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Light Therapy to Improve Sleep Quality in Older Adults Living in Residential Long-Term Care: A Systematic Review

Published:November 18, 2022DOI:https://doi.org/10.1016/j.jamda.2022.10.008

      Abstract

      Objectives

      Because light can regulate sleep rhythms, numerous studies have investigated whether light therapy can improve sleep disorders in older people, but its efficacy remains controversial. Therefore, this systematic review aimed to examine and summarize current evidence about the efficacy of light therapy to improve sleep for older people in residential long-term care.

      Design

      Systematic review.

      Setting and participants

      Older people living in long-term care settings.

      Methods

      Systematic searches were conducted in the databases PubMed, Web of Science, Cochrane, EMBASE, CINAHL, China National Knowledge Infrastructure, China Science and Technology Journal Database, WanFang, Chinese Biomedical Literature Database, and in reference lists within relevant articles. Studies were eligible for inclusion if they evaluated light therapy for older people with sleep disorders in long-term care settings.

      Results

      This systematic review includes 21 articles, summarizing light therapy with different durations and intensities. The light intervention was typically administered between 7:00 and 12:00 am for 30-120 minutes. The interventions lasted from 1 week to several months, and the intensity of the light intervention usually ranged from 2500 to 10,000 lux. Short-term exposure (30-60 minutes) with high light levels (≥10,000 lux), relatively long-term exposure (1-2 hours) with moderate light levels (2500-10,000 lux), or long-term exposure (1-4 hours or full day) with low light levels (≤2500 lux) were associated with improved sleep indicators for older people in long-term care settings.

      Conclusions and implications

      The efficacy of light therapy in long-term care settings may be affected by the duration of exposure, time and length of intervention, intensity of light, and equipment used to administer the therapy. Further research must be conducted to optimize light therapy parameters. Large, high-quality randomized controlled trials are needed to deepen our understanding of the effects of light therapy on sleep in older people living in long-term care settings.

      Keywords

      Sleep disorders are frequently observed in the older adult population. However, they can have serious effects on quality of life and aggravate existing diseases.
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      Association of socioeconomic factors and prevalence of hypertension with sleep disorder among the elderly in rural southwest China.
      The average age of the world's population is steadily increasing, with about 1 billion people aged 65 years or older in 2019. That number is expected to increase to 1.4 billion by 2030 and to 2.1 billion by 2050.
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      Urbanization and population aging: converging trends of demographic transitions in modern world.
      An estimated 40% to 70% of older adults worldwide report chronic sleep problems, with up to 50% of these cases going undiagnosed.
      • Miner B.
      • Kryger M.H.
      Sleep in the aging population.
      The Established Populations for Epidemiologic Studies of the Elderly (EPESE) reported that 43% of participants aged 65-74 years experienced difficulties falling asleep and remaining asleep, and the prevalence of sleep problems increased to 50% among participants aged 75-84 years.
      • Frohnhofen H.
      • Schlitzer J.
      Sleep and sleep disorders in the elderly: Part 1: epidemiology and diagnostics.
      Poor sleep patterns can increase the risk of adverse health outcomes, as well as chronic diseases such as cardiovascular disease, type 2 diabetes, and osteoporosis.
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      Short sleep duration and health outcomes: a systematic review, meta-analysis, and meta-regression.
      Studies have shown that sleep disorders are more common among older people living in long-term care settings than among those living in the general community.
      • Neikrug A.B.
      • Ancoli-Israel S.
      Sleep disturbances in nursing homes.
      A study involving 492 older people who lived in long-term care settings found that >50% reported daytime sleepiness and 60% reported nighttime sleep disturbances.
      • Martin J.L.
      • Webber A.P.
      • Alam T.
      • et al.
      Daytime sleeping, sleep disturbance, and circadian rhythms in the nursing home.
      These results may reflect the environment within residential long-term care, where noise levels, especially at night, may be higher because of activity by roommates and staff,
      • Kim D.E.
      • Yoon J.Y.
      Factors that influence sleep among residents in long-term care facilities.
      ,
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      • Hu Z.
      • Nie Y.
      • et al.
      The prevalence of poor sleep quality and associated risk factors among Chinese elderly adults in nursing homes: A cross-sectional study.
      and where residents may not receive sufficient light exposure during the day.
      • Shochat T.
      • Martin J.
      • Marler M.
      • et al.
      Illumination levels in nursing home patients: effects on sleep and activity rhythms.
      However, drugs used to treat sleep disorders, such as benzodiazepines, are considered unsafe for older people because the drugs may exacerbate their existing risk of drowsiness, cognitive degradation, high risk of fracture, ataxia, drug dependence, and other adverse reactions associated with long-term use.
      • Schroeck J.L.
      • Ford J.
      • Conway E.L.
      • et al.
      Review of safety and efficacy of sleep medicines in older adults.
      Therefore, it is necessary to explore nondrug therapy to improve sleep disorders in older people living in long-term care settings.
      Light plays an important role in maintaining the biological rhythm of the human body: it regulates the input of the physiological pacemaker of the hypothalamus (ie, the suprachiasmatic nucleus) via the retina, and it inhibits the secretion of melatonin.
      • Faulkner S.M.
      • Bee P.E.
      • Meyer N.
      • et al.
      Light therapies to improve sleep in intrinsic circadian rhythm sleep disorders and neuro-psychiatric illness: systematic review and meta-analysis.
      Light therapy has been widely applied as a convenient, safe, nondrug therapy against sleep disorders through its ability to modulate circadian rhythms.
      • Pail G.
      • Huf W.
      • Pjrek E.
      • et al.
      Bright-light therapy in the treatment of mood disorders.
      Different wavelengths of light can activate circadian rhythms in rod cells and cone cells of the retina, with different effects.
      • Mouland J.W.
      • Martial F.
      • Watson A.
      • et al.
      Cones support alignment to an inconsistent world by suppressing mouse circadian responses to the blue colors associated with twilight.
      The duration of light exposure also influences circadian rhythm in different ways.
      • Gammack J.K.
      Light therapy for insomnia in older adults.
      Light therapy has been reported to be effective for improving the sleep of healthy older people
      • Rubiño J.A.
      • Gamundí A.
      • Akaarir M.
      • et al.
      Bright light therapy and circadian cycles in institutionalized elders.
      ,
      • Scheuermaier K.
      • Münch M.
      • Ronda J.M.
      • et al.
      Improved cognitive morning performance in healthy older adults following blue-enriched light exposure on the previous evening.
      and patients with dementia or Parkinson's disease.
      • Videnovic A.
      • Klerman E.B.
      • Wang W.
      • et al.
      Timed light therapy for sleep and daytime sleepiness associated with parkinson disease: a randomized clinical trial.
      ,
      • Tan J.S.I.
      • Cheng L.J.
      • Chan E.Y.
      • et al.
      Light therapy for sleep disturbances in older adults with dementia: a systematic review, meta-analysis and meta-regression.
      It can also improve sleep-wake disorders in patients with seasonal depression, perhaps by altering melatonin secretion patterns.
      Light therapy for older people is easier to apply within long-term care settings than in the general community.
      • Hughes C.M.
      Compliance with medication in nursing homes for older people: resident enforcement or resident empowerment.
      Studies of light therapy in long-term care settings has focused on patients with dementia, in whom it can improve circadian rhythm, sleep disorders, insomnia, and sleep problems.
      • Forbes D.
      • Blake C.M.
      • Thiessen E.J.
      • et al.
      Light therapy for improving cognition, activities of daily living, sleep, challenging behaviour, and psychiatric disturbances in dementia.
      ,
      • Burkhalter H.
      • Wirz-Justice A.
      • Denhaerynck K.
      • et al.
      The effect of bright light therapy on sleep and circadian rhythms in renal transplant recipients: a pilot randomized, multicentre wait-list controlled trial.
      Some studies have even reported benefits on emotion regulation and cognition.
      • Forbes D.
      • Blake C.M.
      • Thiessen E.J.
      • et al.
      Light therapy for improving cognition, activities of daily living, sleep, challenging behaviour, and psychiatric disturbances in dementia.
      ,
      • Kim S.J.
      • Lee S.H.
      • Suh I.B.
      • et al.
      Positive effect of timed blue-enriched white light on sleep and cognition in patients with mild and moderate Alzheimer's disease.
      However, other studies have failed to detect benefits of light therapy, for example, on individuals with seasonal affective disorder,
      • Rohan K.J.
      • Meyerhoff J.
      • Ho S.Y.
      • et al.
      Outcomes one and two winters following cognitive-behavioral therapy or light therapy for seasonal affective disorder.
      cognitive impairment,
      • Wang Z.
      • Zhang Y.
      • Dong L.
      • et al.
      Effects of morning blue-green 500 nm light therapy on cognition and biomarkers in middle-aged and older adults with subjective cognitive decline and mild cognitive impairment: study protocol for a randomized controlled trial.
      ,
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      or older adults with sleep disorders.
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      ,
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      Thus, whether light therapy is effective against sleep disorders remains controversial, particularly for residents of long-term care settings. Furthermore, no evidence-based consensus exists about the optimal parameters for light therapy, such as light intensity and duration.
      This systematic review was to summarize the available evidence about light therapy to improve sleep quality and nighttime sleep in older residents in long-term care settings. Our narrative analysis may give health care providers a clearer understanding of current research on this topic, and it may inspire future studies to address the broad gaps in this field.

      Aims

      The purpose of this review was to evaluate studies addressing the efficacy of light therapy to improve the circadian rhythm and sleep-related outcomes in residents living in long-term care settings.

      Methods

      Search Strategy

      We systematically searched several electronic databases, including PubMed, Web of Science, Cochrane, EMBASE, CINAHL, China National Knowledge Infrastructure, China Science and Technology Journal Database, WanFang, and Chinese Biomedical Literature Database (Supplementary Table 1). We searched for all relevant articles written in English or Chinese that were published until March 29, 2021, and addressed light therapy interventions for older residents of long-term care settings. The following search strings were used in combination with Boolean operators (AND, OR): phototherapy, light therapy, bright light, light exposure, sleep wake disorders, dyssomnia, circadian rhythm, somnolence, insomnia, nursing home, residential facility, assisted living facility, long-term care, and institutionalization. In addition, we used the following Chinese search terms: 光照疗法, 光照治疗, 光照, 睡眠障碍, 睡眠紊乱, and 睡眠. Titles and abstracts of identified published articles were independently reviewed for relevance by 2 authors (M.J.Z., Q.W.). In the case of inconsistencies or lack of agreement, another senior researcher (Z.Z.X.) was consulted for the final decision about inclusion.

      Eligibility Criteria

      Studies were eligible for inclusion if they (1) studied the effect of light therapy on the sleep of people older than 65 years in long-term care settings, (2) had a randomized or nonrandomized design, (3) reported sleep or circadian outcomes, and (4) were published in English or Chinese. Case studies, case series, review articles, commentaries, letters, editorials, and conference abstracts were excluded. If the full text of the study was unavailable, the corresponding authors were contacted and, if necessary, reminders were sent. If sufficient data could not be obtained from the corresponding authors, the study was excluded.

      Methodological Quality Assessment

      The methodological quality of the included articles was rated independently by 2 reviewers (M.J.Z., Q.W.). We assessed the risk of bias using the Cochrane Collaboration’s revised tool for assessing risk of bias of randomized controlled trials.
      • Sterne J.A.C.
      • Savović J.
      • Page M.J.
      • et al.
      RoB 2: a revised tool for assessing risk of bias in randomised trials.
      The quality checklist provided by this assessment tool covers 7 domains: (1) random sequence generation, (2) allocation concealment, (3) blinding of participants and personnel, (4) blinding of outcome assessment, (5) incomplete outcome data, (6) selective reporting, and (7) other sources of bias. A plus symbol (+) corresponded to “low risk of bias”; a minus symbol (–), “high risk of bias”; and a question mark (?), “unclear risk of bias.” The results are displayed in Table 1.
      Table 1Cochrane Handbook for Systematic Reviews of Interventions Quality Assessment Randomized Controlled Trials
      DomainAncoli-Israel et al 2003
      • Ancoli-Israel S.
      • Gehrman P.
      • Martin J.L.
      • et al.
      Increased light exposure consolidates sleep and strengthens circadian rhythms in severe Alzheimer's disease patients.
      Gasio et al 2003
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      Dowling et al 2005
      • Dowling G.
      • Mastick J.
      • Hubbard E.
      • et al.
      Effect of timed bright light treatment for rest-activity disruption in institutionalized patients with Alzheimer's disease.
      Gammack et al 2009
      • Gammack J.K.
      • Burke J.M.
      Natural light exposure improves subjective sleep quality in nursing home residents.
      Wu et al 2015
      • Wu M.
      • Sung H.
      • Lee W.
      • et al.
      The effects of light therapy on depression and sleep disruption in older adults in a long-term care facility.
      Düzgün et al 2017
      • Duzgun G.
      • Akyol A.D.
      Effect of natural sunlight on sleep problems and sleep quality of the elderly staying in the nursing home.
      Figueiro et al 2019
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      Lan et al 2019
      • Lan L.
      Effect of light duration on the clinical outcome of full-spectrum therapy for Alzheimer's disease patients with sleep disorders.
      Linander et al 2020
      • Linander C.B.
      • Kallemose T.
      • Joergensen L.M.
      • et al.
      The effect of circadian-adjusted LED-based lighting on sleep, daytime sleepiness and biomarkers of inflammation in a randomized controlled cross-over trial by pragmatic design in elderly care home dwellers.
      Juda et al 2020
      • Juda M.
      • Liu-Ambrose T.
      • Feldman F.
      • et al.
      Light in the senior home: effects of dynamic and individual light exposure on sleep, cognition, and well-being.
      Zhang et al 2021
      • Zhang J.
      • Wu W.
      • Huang lc
      • et al.
      Effect of light therapy on circadian sleep disorder in the elderly.
      Random sequence generation (selection bias)+?+++++++++
      Allocation concealment (selection bias)??+????+++
      Blinding of participants and personnel (performance bias)+?++??++??
      Blinding of outcome assessment (detection bias)+++++?+++++
      Incomplete outcome data (attrition bias)+++-+++??++
      Selective reporting (reporting bias)++++???++?
      Other source of bias (other bias)?+???++????
      Plus symbol: low risk of bias; minus symbol: high risk of bias; question mark symbol: unclear risk of bias.
      The ROBINS-I assessing the risk of bias in nonrandomized studies of interventions
      • Sterne J.A.
      • Hernán M.A.
      • Reeves B.C.
      • et al.
      ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions.
      was used to assess the risk of bias for quantitative studies that compared the efficacy of an intervention in 2 or more groups of individuals. This tool includes 7 domains: (1) bias due to confounding, (2) bias in selection of participants into the study, (3) bias in classification of interventions, (4) bias due to deviations from intended interventions, (5) bias due to missing data, (6) bias in measurement of outcomes, and (7) bias in selection of the reported results. Each of these domains could be rated as low risk, moderate risk, serious risk, critical risk, or no information. The results are displayed in Table 2.
      Table 2Risk of Bias Summary for Nonrandomized Controlled Trials by ROBINS-I
      First Author (Year)Bias Due to ConfoundingBias in Selection of Participants Into the StudyBias in Classification of InterventionsBias Due to Deviations From Intended InterventionsBias Due to Missing DataBias in Measurement of OutcomesBias in Selection of the Reported ResultOverall Bias
      Sansal, 2020
      • Sansal K.E.
      • Tanriover S.H.
      • Turkuler Aka B.
      Effects of outdoor natural light exposure on sleep quality in the elderly.
      Not applicableLowLowLowLowNo informationLowModerate
      Sekiguchi, 2017
      • Sekiguchi H.
      • Iritani S.
      • Fujita K.
      Bright light therapy for sleep disturbance in dementia is most effective for mild to moderate Alzheimer's type dementia: a case series.
      LowLowLowModerateLowLowLowModerate
      Figueiro, 2014
      • Figueiro M.G.
      • Plitnick B.A.
      • Lok A.
      • et al.
      Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities.
      Not applicableLowSeriousNo informationLowLowLowSerious
      Akyar, 2013
      • Akyar I.
      • Akdemir N.
      The effect of light therapy on the sleep quality of the elderly: an intervention study.
      LowLowNo informationLowNo informationNo informationNo informationModerate
      Sloane, 2007
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      LowSeriousLowLowLowLowLowSerious
      Fetveit, 2005
      • Fetveit A.
      • Bjorvatn B.
      Bright-light treatment reduces actigraphic measured daytime sleep in nursing home patients with dementia - A pilot study.
      LowSeriousSeriousLowLowLowLowSerious
      Skjerve, 2004
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      LowLowNo informationLowLowLowLowModerate
      Fetveit, 2004
      • Fetveit A.
      • Bjorvatn B.
      The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.
      LowNo informationLowLowLowLowLowModerate
      Fetveit, 2003
      • Fetveit A.
      • Skjerve A.
      • Bjorvatn B.
      Bright light treatment improves sleep in institutionalised elderly - an open trial.
      LowNo informationLowLowLowLowLowModerate
      Koyama, 1999
      • Koyama E.
      • Matsubara H.
      • Nakano T.
      Bright light treatment for sleep-wake disturbances in aged individuals with dementia.
      Not applicableNo informationLowLowLowLowLowModerate

      Analysis Approach

      The included studies were heterogeneous in light therapy methods and sleep outcomes, which made meta-analysis impossible. Hence, narrative analysis was conducted based on whether sleep outcomes were subjective or objective, and based on the particular light therapy applied.

      Results

      Study Selection

      The search strategy identified a total of 472 articles. Two authors reviewed titles and abstracts and selected 80 articles for further review. Manual searching of reference lists within these 80 articles and a search of the Cochrane Central Register of Controlled Trials revealed no additional studies. Excluded articles were duplicates, protocols, review articles, case reports, reports not published in English or Chinese, and studies not involving light therapy intervention.
      Of the 80 articles, another 59 were excluded after full-text review. Excluded articles did not feature light therapy as a primary intervention, they were not conducted in long-term care settings, their method was only qualitative, they did not report sleep or circadian rhythm outcomes, or the full text was unavailable and efforts to obtain sufficient data from the corresponding author failed.
      Ultimately, 21 articles were included in this systematic review. A PRISMA flow diagram of the search process is presented in Figure 1.
      Figure thumbnail gr1
      Fig. 1PRISMA flow diagram of study inclusion. CNKI, China National Knowledge Infrastructure; CBM, Chinese Biomedical Literature Database; VIP, China Science and Technology Journal Database.

      Characteristics

      This review included 10 nonrandomized pilot studies and 11 randomized controlled trials. The total sample in this review was 748 participants, with sample size per study ranging from 6 to 92. The mean age of participants in each study ranged from 68.26 to 89 years. Nearly half the studies recruited older people with sleep disorders and dementia, 9 studies recruited only older adults with sleep disorders, and 2 studies recruited older people with sleep disorders and depression. Most of the studies were conducted in North America. The characteristics of included articles are presented in Table 3.
      Table 3Characteristics of Studies Included in the Systematic Review
      First Author and YearStudy DesignParticipantsInterventionDuration and Frequency of Intervention; Follow-Up (If Any)Tools Used to Measure Outcomes
      Sansal, 2020
      • Sansal K.E.
      • Tanriover S.H.
      • Turkuler Aka B.
      Effects of outdoor natural light exposure on sleep quality in the elderly.
      Pretest-posttest designOlder patients with sleep disorders (n = 39); no control groupIntervention: Outdoor natural light (>10,000 lux),

      Control: No control group
      Two 5-day interventions (9:00-9:40 am, 40 min)MEQ, PSQI, PROMIS, RCSQ
      Linander
      • Linander C.B.
      • Kallemose T.
      • Joergensen L.M.
      • et al.
      The effect of circadian-adjusted LED-based lighting on sleep, daytime sleepiness and biomarkers of inflammation in a randomized controlled cross-over trial by pragmatic design in elderly care home dwellers.
      , 2020
      Randomized controlled with crossoverOlder patients with sleep disorders (n = 34):

      Intervention group: n = 19

      Control group: n = 15
      Intervention: Circadian rhythm LED lamp

      (300/400/300 lux 12-14 h)

      Control: Standard light

      (70/70/150 lux 12-14 h)
      16 wk; 8 wk for all conditionsPSQI, ESS
      Juda
      • Juda M.
      • Liu-Ambrose T.
      • Feldman F.
      • et al.
      Light in the senior home: effects of dynamic and individual light exposure on sleep, cognition, and well-being.
      , 2020
      Randomized controlled with crossoverOlder patients with disturbed sleep

      patterns (n = 14)
      Intervention: LED lighting system

      Control: Standard light
      10 wk, 5 wk for all conditionsActigraph, μMCTQ
      Figueiro, 2019
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      Randomized controlled with crossoverOlder patients with

      dementia and disturbed sleep (n = 46)
      Intervention: LED lighting system (5000 lux)

      Control: LED lighting system (2000lux)
      16 wk; 8 wk for all conditionsActigraph, PSQI
      Sekiguchi, 2017
      • Sekiguchi H.
      • Iritani S.
      • Fujita K.
      Bright light therapy for sleep disturbance in dementia is most effective for mild to moderate Alzheimer's type dementia: a case series.
      Pretest-posttest designOlder people with dementia and disturbed sleep patterns (n=17); no control groupIntervention: Light box at 900-1000 lux

      Control: No control group
      Two weeks for (1) 1 h at 900-1000 lux at a distance longer than 0.5 m; and (2) 2 h at 2500-5000 lux at a distance of 1 mNPI-NH
      Düzgün, 2017
      • Duzgun G.
      • Akyol A.D.
      Effect of natural sunlight on sleep problems and sleep quality of the elderly staying in the nursing home.
      Randomized controlledOlder people with sleep disorders (n=61):

      Intervention group: n=30

      Control group: n=31
      Intervention: Outdoor natural light

      Control: Usual indoor light
      5 days for up to 2 h each day (8:00-10:00 am) in subgroups:

      (1) 30-60 min

      (2) 60-90 min

      (3) 90-120 min

      (4) 120 min
      PSQI
      Wu, 2015
      • Wu M.
      • Sung H.
      • Lee W.
      • et al.
      The effects of light therapy on depression and sleep disruption in older adults in a long-term care facility.
      Randomized controlledOlder people with depression and disturbed sleep patterns (n=65):

      Intervention group: n=34

      Control group: n=31
      Intervention: Light box at 10,000 lux

      Control: Routine care, no light treatment
      4 wk at 30 min per day (3 times a week)Incidence of sleep disruption
      Figueiro, 2014
      • Figueiro M.G.
      • Plitnick B.A.
      • Lok A.
      • et al.
      Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities.
      Pretest-posttest designOlder people with dementia, depression, and disturbed sleep patterns (n=14); no control groupIntervention: Tailored lighting system (bluish-white light)

      Control: No control group
      4 wk at 10 h/d turned on at the residents’ waking time (6:00 am to 8:00 am) and turned off at 6:00 pmDaysimeter, PSQI
      Akyar, 2013
      • Akyar I.
      • Akdemir N.
      The effect of light therapy on the sleep quality of the elderly: an intervention study.
      Pretest-posttest designOlder people with disturbed sleep patterns (n=24); no control groupIntervention: Light box at 10,000 lux

      Control: No control group
      4 wk at 30 min/dPSQI
      Gammack, 2009
      • Gammack J.K.
      • Burke J.M.
      Natural light exposure improves subjective sleep quality in nursing home residents.
      Randomized controlledOlder people with disturbed sleep patterns (n=24):

      Intervention group: n=12

      Control group: n=12
      Intervention: Outdoor natural light

      Control: Usual indoor light
      21 d at 60 min per day during 07:00-12:00 amSelf-reported sleep quality
      Sloane, 2007
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      Pretest-posttest designOlder people with dementia and disturbed sleep patterns (n=66)Intervention: LED lighting system (2500 lux) in 3 subgroups:

      (1) Morning bright light

      (2) Evening bright light

      (3) All-day bright light

      Control: No control group
      3 wk for all 3 subgroups:

      (1) 07:00-11:00 am

      (2) 04:00-08:00 pm

      (3) All day (07:00-11:00 am + 04:00-08:00 pm)
      Actiwatch
      Fetveit, 2005
      • Fetveit A.
      • Bjorvatn B.
      Bright-light treatment reduces actigraphic measured daytime sleep in nursing home patients with dementia - A pilot study.
      Pretest-posttest designOlder people patients with disturbed sleep patterns (n=11); no control groupIntervention: Light box at 6000-8000 lux at a distance of 60-70 cm

      Control: No control group
      2 wk for 30 min between 08:00 and 11:00 am; follow-up of 16 wk after treatmentActiwatch
      Dowling, 2005
      • Dowling G.
      • Mastick J.
      • Hubbard E.
      • et al.
      Effect of timed bright light treatment for rest-activity disruption in institutionalized patients with Alzheimer's disease.
      Randomized controlledOlder people with dementia and disturbed sleep patterns (n=70):

      Intervention groups: (1) n=29 and (2) n=24

      Control group: n=17
      Intervention: Outdoor natural light (2500 lux)

      (1) Morning bright light

      (2) Evening bright light

      Control: Usual indoor light (150-200 lux)
      10 wk (5 d/wk)

      (1) 09.30-10.30 am

      (2) 03.30-4.30 pm
      Actiwatch
      Skjerve, 2004
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      Pretest-posttest designOlder people with severe dementia and disturbed sleep patterns (n=10); no control groupIntervention: Light box (5000-8000 lux)

      Control: No control group
      4 wk at 45 min/d; follow-up of 2 wk after treatmentActigraphy
      Fetveit, 2004
      • Fetveit A.
      • Bjorvatn B.
      The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.
      Pretest-posttest designOlder people with dementia and disturbed sleep patterns (n=11); no control groupIntervention: Light box (6000-8000 lux)

      Control: No control group
      2 wk at 2 h/d (08:00-11:00 am); follow-up of 16 wk after treatmentActiwatch
      Ancoli-Israel, 2003
      • Ancoli-Israel S.
      • Gehrman P.
      • Martin J.L.
      • et al.
      Increased light exposure consolidates sleep and strengthens circadian rhythms in severe Alzheimer's disease patients.
      Randomized controlledOlder people with dementia and disturbed sleep patterns (n=92)

      Intervention groups:

      (1) n = 31 and (2) n = 30

      Control group: n = 31
      Intervention: Light box

      (1) Evening bright light (2500 lux, 05:30-07:30 pm)

      (2) Morning bright light (2500 lux, 09.30-11.30 am)

      Control: Dim red light (<300 lux, 09:30-11:30 am)
      10 d at 2 h/d; 2 follow-up points at 5 d and 5 wk after treatmentActillume
      Fetveit, 2003
      • Fetveit A.
      • Skjerve A.
      • Bjorvatn B.
      Bright light treatment improves sleep in institutionalised elderly - an open trial.
      Pretest-posttest designOlder people with disturbed sleep patterns (n=11); no control groupIntervention: Light box at 6000-8000 lux at a distance of 60-70 cm

      Control: No control group
      2 wk at 2 h/d (08:00-11:00 am); follow-up of 2 wk after treatmentActiwatch
      Gasio, 2003
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      Randomized controlledOlder people with dementia and disturbed sleep patterns (n=13):

      Intervention group: n=4

      Control group: n=9
      Intervention:

      Dawn-dusk simulator (0.001–400 lux)

      Control: Dim red light (<5 lux)
      3 wkActigraphy
      Koyama, 1999
      • Koyama E.
      • Matsubara H.
      • Nakano T.
      Bright light treatment for sleep-wake disturbances in aged individuals with dementia.
      Pretest-posttest designOlder people with dementia and disturbed sleep patterns (n=6); no control groupIntervention: Desktop type and flat panel tray type (4000 lux at eye)

      Control: No control group
      From 30 to 96 d for

      (1) 2 h/d a day (9:30-11:30 am) or

      (2) 1 h a day (11:00-12:00 am)
      Nursing staff observations
      Zhang, 2021
      • Zhang J.
      • Wu W.
      • Huang lc
      • et al.
      Effect of light therapy on circadian sleep disorder in the elderly.
      Randomized controlledOlder people with disturbed sleep patterns (n=60):

      Intervention group 1: n=15

      Intervention group 2: n=15

      Intervention group 3: n=15

      Control group: n=15
      Intervention: Bright light (10,000 lux)

      Control group:

      Wearing an eye mask during exposure to bright light (10,000 lux)
      Exposure for

      (1) 0.5 h a day

      (2) 1 h a day

      (3) 2 h a day
      HAMD, HAMA, ASI, PSQI
      Lan, 2019
      • Lan L.
      Effect of light duration on the clinical outcome of full-spectrum therapy for Alzheimer's disease patients with sleep disorders.
      Randomized controlledOlder people with dementia and disturbed sleep patterns (n=60):

      Intervention group 1: n=20

      Intervention group 2: n=20

      Intervention group 3: n=20
      Intervention:

      Light box (10,000 lux)
      Exposure for (08:00-11:00 am)

      (1) 0.5 h a day

      (2) 1 h a day

      (3) 2 h a day
      ESS, PSQI, NPI, GDS, MMSE
      ASI, Athens Insomnia Scale; ESS, Epworth Sleep Scale; GDS, Global Deterioration Scale; HAMD, Hamilton Depression Scale; HAMA, Hamilton Anxiety Scale; MEQ, Morningness-Eveningness Questionnaire; MMSE, Mini Mental State Examination; NPI-NH, Neuropsychiatric Inventory (Nursing Home Version); RCSQ, Richards-Campbell Sleep Questionnaire.

      Methods and Effects of Light Therapy

      Light therapy in the included studies was delivered in a variety of ways. For example, outdoor exposure to natural light,
      • Gammack J.K.
      • Burke J.M.
      Natural light exposure improves subjective sleep quality in nursing home residents.
      light boxes placed approximately 1 m from the participant’s field of vision,
      • Eastman C.I.
      • Young M.A.
      • Fogg L.F.
      • et al.
      Bright light treatment of winter depression: a placebo-controlled trial.
      ceiling-mounted light-emitting diode (LED) lighting systems providing fixed or dynamic ambient room light,
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      and “natural” light therapy simulating the transition between dawn and dusk.
      • Terman M.
      • Schlager D.
      • Fairhurst S.
      • et al.
      Dawn and dusk simulation as a therapeutic intervention.
      This last method, called dawn-dusk simulation therapy, continuously adjusts the lighting level as the individual sleeps, based on the rate of change between pre-dusk and dawn, thereby adapting the therapy to the individual's habitual sleep time.
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      The times of day when lighting intervention was administered also varied, including morning, midday, and whole day. The interventions lasted from 1 week to several months and were usually provided between 7:00 and 12:00 am. Intensity of the light ranged from 2500 to higher than 10,000 lux.
      We summarized differences in exposure duration, illumination and spectrum, as well as the specific time when the light intervention was administered. Most studies combined light intensity and duration of exposure in such a way that lower light intensity was administered for longer times, such as >10,000 lux for 30-60 minutes,
      • Duzgun G.
      • Akyol A.D.
      Effect of natural sunlight on sleep problems and sleep quality of the elderly staying in the nursing home.
      ,
      • Lan L.
      Effect of light duration on the clinical outcome of full-spectrum therapy for Alzheimer's disease patients with sleep disorders.
      ,
      • Sansal K.E.
      • Tanriover S.H.
      • Turkuler Aka B.
      Effects of outdoor natural light exposure on sleep quality in the elderly.
      ,
      • Akyar I.
      • Akdemir N.
      The effect of light therapy on the sleep quality of the elderly: an intervention study.
      ,
      • Fetveit A.
      • Bjorvatn B.
      Bright-light treatment reduces actigraphic measured daytime sleep in nursing home patients with dementia - A pilot study.
      ,
      • Zhang J.
      • Wu W.
      • Huang lc
      • et al.
      Effect of light therapy on circadian sleep disorder in the elderly.
      2500 to 10,000 lux for 1-2 hours,
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      ,
      • Wu M.
      • Sung H.
      • Lee W.
      • et al.
      The effects of light therapy on depression and sleep disruption in older adults in a long-term care facility.
      ,
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      ,
      • Fetveit A.
      • Bjorvatn B.
      The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.
      • Fetveit A.
      • Skjerve A.
      • Bjorvatn B.
      Bright light treatment improves sleep in institutionalised elderly - an open trial.
      • Koyama E.
      • Matsubara H.
      • Nakano T.
      Bright light treatment for sleep-wake disturbances in aged individuals with dementia.
      or <2500 lux for 1-4 hours or an entire day.
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      ,
      • Dowling G.
      • Mastick J.
      • Hubbard E.
      • et al.
      Effect of timed bright light treatment for rest-activity disruption in institutionalized patients with Alzheimer's disease.
      ,
      • Linander C.B.
      • Kallemose T.
      • Joergensen L.M.
      • et al.
      The effect of circadian-adjusted LED-based lighting on sleep, daytime sleepiness and biomarkers of inflammation in a randomized controlled cross-over trial by pragmatic design in elderly care home dwellers.
      ,
      • Sekiguchi H.
      • Iritani S.
      • Fujita K.
      Bright light therapy for sleep disturbance in dementia is most effective for mild to moderate Alzheimer's type dementia: a case series.
      ,
      • Figueiro M.G.
      • Plitnick B.A.
      • Lok A.
      • et al.
      Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities.
      The literature suggests that lighting intensity should be increased for more serious sleep disorders.
      The wavelength of light is also an important factor in light therapy. One study reported that the circadian rhythm system is most sensitive to short-wavelength (blue) light, with sensitivity peaking at 460 nm.
      • Figueiro M.G.
      • Plitnick B.A.
      • Lok A.
      • et al.
      Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities.
      In support of this, another study found that increasing the shorter wavelengths (blue and white) in moderate-intensity light improved objective and subjective sleep as well as behavioral indicators.
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      Interstudy differences in outcome measures made it impossible to compare efficacy directly across light therapy methods. Studies using stationary light-emitting devices reported efficacy.
      • Ancoli-Israel S.
      • Gehrman P.
      • Martin J.L.
      • et al.
      Increased light exposure consolidates sleep and strengthens circadian rhythms in severe Alzheimer's disease patients.
      ,
      • Lan L.
      Effect of light duration on the clinical outcome of full-spectrum therapy for Alzheimer's disease patients with sleep disorders.
      We could not assess the durability of benefits because most studies did not perform follow-up after treatment.

      Effects of Light Therapy on Objective Sleep Outcomes and Circadian Rhythm

      Objective sleep and circadian rhythms are usually evaluated using actigraphy. The indicators of objective sleep include total sleep time, sleep efficiency, sleep onset latency, and wake after sleep onset. The parameters of rest-activity cycle of circadian rhythm include intraday stability, intraday variability, and relative amplitude.
      Ten studies
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      ,
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      ,
      • Ancoli-Israel S.
      • Gehrman P.
      • Martin J.L.
      • et al.
      Increased light exposure consolidates sleep and strengthens circadian rhythms in severe Alzheimer's disease patients.
      ,
      • Duzgun G.
      • Akyol A.D.
      Effect of natural sunlight on sleep problems and sleep quality of the elderly staying in the nursing home.
      ,
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      ,
      • Juda M.
      • Liu-Ambrose T.
      • Feldman F.
      • et al.
      Light in the senior home: effects of dynamic and individual light exposure on sleep, cognition, and well-being.
      ,
      • Figueiro M.G.
      • Plitnick B.A.
      • Lok A.
      • et al.
      Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities.
      ,
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      • Fetveit A.
      • Bjorvatn B.
      Bright-light treatment reduces actigraphic measured daytime sleep in nursing home patients with dementia - A pilot study.
      • Fetveit A.
      • Bjorvatn B.
      The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.
      investigated the effects of light therapy on objective sleep outcomes and circadian rhythm. Nine studies included older adults with sleep disorders or dementia, whereas one included older adults with sleep disorders and depression. In these studies, light therapy was administered between 7:00 and 12:00 am for at least 30 minutes, and an activity recorder was used to record objective sleep parameters.
      Some studies
      • Figueiro M.G.
      • Plitnick B.A.
      • Lok A.
      • et al.
      Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities.
      ,
      • Fetveit A.
      • Bjorvatn B.
      Bright-light treatment reduces actigraphic measured daytime sleep in nursing home patients with dementia - A pilot study.
      ,
      • Fetveit A.
      • Bjorvatn B.
      The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.
      used mainly sleep latency and sleep efficiency as outcome indicators, and the results were positive: light therapy reduced sleep latency in residents of long-term care settings, improving sleep efficiency and the sleep-wake cycle. In other words, readjustment of circadian rhythm after light irradiation led to earlier and easier sleep. For example, one study
      • Fetveit A.
      • Bjorvatn B.
      The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.
      found that light therapy increased the sleep efficiency from 73% to 86%. In studies of residents of long-term care settings, 3
      • Ancoli-Israel S.
      • Gehrman P.
      • Martin J.L.
      • et al.
      Increased light exposure consolidates sleep and strengthens circadian rhythms in severe Alzheimer's disease patients.
      ,
      • Fetveit A.
      • Bjorvatn B.
      Bright-light treatment reduces actigraphic measured daytime sleep in nursing home patients with dementia - A pilot study.
      ,
      • Fetveit A.
      • Bjorvatn B.
      The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.
      showed that morning light therapy consolidated nighttime sleep and strengthened circadian rhythms, whereas 2
      • Fetveit A.
      • Bjorvatn B.
      Bright-light treatment reduces actigraphic measured daytime sleep in nursing home patients with dementia - A pilot study.
      ,
      • Fetveit A.
      • Bjorvatn B.
      The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.
      reported a significant reduction in daytime sleep and a reduction in total nocturnal wake time.
      Among 5 studies
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      ,
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      ,
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      ,
      • Juda M.
      • Liu-Ambrose T.
      • Feldman F.
      • et al.
      Light in the senior home: effects of dynamic and individual light exposure on sleep, cognition, and well-being.
      ,
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      using intraday stability and relative amplitude as outcome indicators, 2
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      ,
      • Juda M.
      • Liu-Ambrose T.
      • Feldman F.
      • et al.
      Light in the senior home: effects of dynamic and individual light exposure on sleep, cognition, and well-being.
      found that daytime light therapy significantly improved both indicators, reducing intraday stability by 0.749, increasing relative amplitude by 0.666, stimulating circadian rhythm, and reducing rhythm fragmentation. The other 3 studies,
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      ,
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      ,
      • Dowling G.
      • Mastick J.
      • Hubbard E.
      • et al.
      Effect of timed bright light treatment for rest-activity disruption in institutionalized patients with Alzheimer's disease.
      ,
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      however, found no significant improvement in outcome indicators. In one
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      of these studies, light therapy did not significantly alter intraday stability, intraday variability, or relative amplitude; nevertheless, therapy shifted the main sleep episode 74 minutes earlier and led to shorter sleep latency, longer sleep duration, and less nocturnal activity. In 2 other studies,
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      ,
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      exposing participants with severe dementia to morning light did not significantly alter the measures of circadian rhythm, yet it did significantly increase nocturnal sleep time, as measured by actigraphy, in one
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      of those studies. The authors of that work concluded that the treatment period of 4 weeks may not have been sufficient to affect patients with severe dementia.

      Effects of Light Therapy on Subjective Sleep Outcomes and Daytime Sleepiness

      Ten studies
      • Wu M.
      • Sung H.
      • Lee W.
      • et al.
      The effects of light therapy on depression and sleep disruption in older adults in a long-term care facility.
      • Duzgun G.
      • Akyol A.D.
      Effect of natural sunlight on sleep problems and sleep quality of the elderly staying in the nursing home.
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      • Lan L.
      Effect of light duration on the clinical outcome of full-spectrum therapy for Alzheimer's disease patients with sleep disorders.
      ,
      • Sansal K.E.
      • Tanriover S.H.
      • Turkuler Aka B.
      Effects of outdoor natural light exposure on sleep quality in the elderly.
      ,
      • Figueiro M.G.
      • Plitnick B.A.
      • Lok A.
      • et al.
      Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities.
      ,
      • Akyar I.
      • Akdemir N.
      The effect of light therapy on the sleep quality of the elderly: an intervention study.
      ,
      • Koyama E.
      • Matsubara H.
      • Nakano T.
      Bright light treatment for sleep-wake disturbances in aged individuals with dementia.
      ,
      • Zhang J.
      • Wu W.
      • Huang lc
      • et al.
      Effect of light therapy on circadian sleep disorder in the elderly.
      reported the effect of light therapy on sleep outcomes and daytime sleepiness. Subjective sleep assessment usually involves sleep diaries and sleep questionnaires, such as the Pittsburgh Sleep Quality Index (PSQI), whereas daytime sleepiness is usually assessed using the Epworth Sleep Scale. Three studies
      • Lan L.
      Effect of light duration on the clinical outcome of full-spectrum therapy for Alzheimer's disease patients with sleep disorders.
      ,
      • Akyar I.
      • Akdemir N.
      The effect of light therapy on the sleep quality of the elderly: an intervention study.
      ,
      • Zhang J.
      • Wu W.
      • Huang lc
      • et al.
      Effect of light therapy on circadian sleep disorder in the elderly.
      exposed residents of long-term care settings to bright morning light of 10,000 lux. All 3 of these studies measured significant improvements in the PSQI (the PSQI score decreased by 7.04 on average), whereas one
      • Zhang J.
      • Wu W.
      • Huang lc
      • et al.
      Effect of light therapy on circadian sleep disorder in the elderly.
      of the 3 studies also reported significant improvement in scores on the Athens Insomnia Scale, and another
      • Lan L.
      Effect of light duration on the clinical outcome of full-spectrum therapy for Alzheimer's disease patients with sleep disorders.
      of the 3 studies reported significant improvement on the Epworth Sleep Scale, which measures daytime sleepiness (The total score of the Athens Insomnia Scale and Epworth Sleep Scale was 24 points, and the scores decreased by 6.16 and 7.57, respectively), suggesting that morning light therapy can effectively improve the sleep quality and daytime sleepiness of long-term care setting residents. Additional studies have reported significant improvement in subjective sleep measures using different light therapy methods,
      • Duzgun G.
      • Akyol A.D.
      Effect of natural sunlight on sleep problems and sleep quality of the elderly staying in the nursing home.
      ,
      • Sansal K.E.
      • Tanriover S.H.
      • Turkuler Aka B.
      Effects of outdoor natural light exposure on sleep quality in the elderly.
      ,
      • Figueiro M.G.
      • Plitnick B.A.
      • Lok A.
      • et al.
      Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities.
      such as tailored interventions and natural bright sunshine in the morning.
      On the other hand, one randomized crossover trial
      • Linander C.B.
      • Kallemose T.
      • Joergensen L.M.
      • et al.
      The effect of circadian-adjusted LED-based lighting on sleep, daytime sleepiness and biomarkers of inflammation in a randomized controlled cross-over trial by pragmatic design in elderly care home dwellers.
      in which older patients with different degrees of dementia were exposed to LED or traditional light for 8 weeks reported no significant change in the sleep questionnaires. This discrepancy from other studies may reflect the crossover trial’s small sample and the heterogeneity of dementia in the sample, even after randomization. In one study
      • Koyama E.
      • Matsubara H.
      • Nakano T.
      Bright light treatment for sleep-wake disturbances in aged individuals with dementia.
      based on sleep diaries, 6 residents of 2 long-term care settings with Alzheimer's disease were exposed to bright morning light, and caregivers recorded their sleep patterns in an observational diary. Three subjects experienced improved sleep efficiency and decreased daytime sleepiness, whereas sleep onset time was shifted earlier in the other 3 subjects. The small sample in this study limits the reliability of its findings. In another study
      • Wu M.
      • Sung H.
      • Lee W.
      • et al.
      The effects of light therapy on depression and sleep disruption in older adults in a long-term care facility.
      based on sleep diaries, administering light therapy for 30 minutes in the morning to 34 older adult patients sitting in front of a 10,000-lux light box did not significantly improve sleep disruption.
      Taken together, these studies of light therapy suggest that it has variable, but usually positive, effects on sleep quality and circadian rhythms in residents living in long-term care settings. Very few studies have reported adverse reactions after light therapy.

      Discussion

      Light levels in residential long-term care facilities are far below what is considered necessary for circadian entrainment. Environmental assessment of dementia care institutions
      • Sloane P.D.
      • Mitchell C.M.
      • Weisman G.
      • et al.
      The Therapeutic Environment Screening Survey for Nursing Homes (TESS-NH): an observational instrument for assessing the physical environment of institutional settings for persons with dementia.
      ,
      • Sinoo M.M.
      • van Hoof J.
      • Kort H.S.M.
      Light conditions for older adults in the nursing home: assessment of environmental illuminances and colour temperature.
      found that even in summer, the median vertical illumination is less than 300 lux, far below the daylight range of 6500-130,000 lux.
      • Kolberg E.
      • Pallesen S.
      • Hjetland G.J.
      • et al.
      Insufficient melanopic equivalent daylight illuminance in nursing home dementia units across seasons and gaze directions.
      ,
      • Norton T.T.
      • Siegwart Jr., J.T.
      Light levels, refractive development, and myopia--a speculative review.
      At the same time, most older people in long-term care settings have limited mobility and cognitive decline.
      • Estabrooks C.A.
      • Poss J.W.
      • Squires J.E.
      • et al.
      A profile of residents in prairie nursing homes.
      Light therapy in long-term care settings may improve residents’ sleep, and compliance with such therapy is easier to ensure within care facilities than in the general community.
      • Hughes C.M.
      Compliance with medication in nursing homes for older people: resident enforcement or resident empowerment.
      ,
      • Beck A.M.
      • Gøgsig Christensen A.
      • Stenbæk Hansen B.
      • et al.
      Study protocol: cost-effectiveness of multidisciplinary nutritional support for undernutrition in older adults in nursing home and home-care: cluster randomized controlled trial.
      Despite these potential benefits of light therapy, our review of the literature revealed a lack of research in this area as well as substantial heterogeneity of interventions and evaluation indicators. Our review, although narrative, summarizes common themes in this diverse evidence base and may help guide future research into light therapy for improving the circadian rhythm and sleep-related outcomes in residents of long-term care settings.
      Despite the variety of light therapy methods and equipment, most studies have concluded that light therapy can help improve the sleep quality of residents in long-term care settings. Moreover, the various studies demonstrate that the effects of light therapy depend on the intensity, duration, and wavelength of light, as well as on the individual’s health condition.
      Light therapy can be delivered indoors, such as using a light box or table, light therapy glasses, or indoor ambient light. Most studies have used light boxes or tables. Participants sit in front of a lamp and are required to observe the light frequently. However, this fixed-light therapy device has certain limitations
      • Kirschbaum-Lesch I.
      • Gest S.
      • Legenbauer T.
      • et al.
      Feasibility and efficacy of bright light therapy in depressed adolescent inpatients.
      • Hjetland G.J.
      • Kolberg E.
      • Pallesen S.
      • et al.
      Ambient bright light treatment improved proxy-rated sleep but not sleep measured by actigraphy in nursing home patients with dementia: a placebo-controlled randomised trial.
      • Liu C.R.
      • Liou Y.M.
      • Jou J.H.
      Ambient bright lighting in the morning improves sleep disturbances of older adults with dementia.
      : its inflexible format means that it is difficult to integrate into daily life, and individuals may feel uncomfortable and tired if they remain near the light box for a long time.
      • Kirschbaum-Lesch I.
      • Gest S.
      • Legenbauer T.
      • et al.
      Feasibility and efficacy of bright light therapy in depressed adolescent inpatients.
      Such therapy may be particularly challenging for patients with cognitive impairment or moderate or severe dementia,
      • Ismail Z.
      • Smith E.E.
      • Geda Y.
      • et al.
      Neuropsychiatric symptoms as early manifestations of emergent dementia: provisional diagnostic criteria for mild behavioral impairment.
      ,
      • Lyketsos C.G.
      • Carrillo M.C.
      • Ryan J.M.
      • et al.
      Neuropsychiatric symptoms in Alzheimer's disease.
      who exhibit abnormal behavior and may be unable to concentrate or remain seated for a long time.
      • Sekiguchi H.
      • Iritani S.
      • Fujita K.
      Bright light therapy for sleep disturbance in dementia is most effective for mild to moderate Alzheimer's type dementia: a case series.
      This type of light therapy therefore creates challenges for the staff of residential care settings.
      • Hjetland G.J.
      • Kolberg E.
      • Pallesen S.
      • et al.
      Ambient bright light treatment improved proxy-rated sleep but not sleep measured by actigraphy in nursing home patients with dementia: a placebo-controlled randomised trial.
      More flexible is light therapy based on indoor ambient light or light therapy glasses.
      • Liu C.R.
      • Liou Y.M.
      • Jou J.H.
      Ambient bright lighting in the morning improves sleep disturbances of older adults with dementia.
      Relaying on indoor light means that all residents can receive light therapy at the same time without intervention from staff.
      • Kolberg E.
      • Hjetland G.J.
      • Thun E.
      • et al.
      The effects of bright light treatment on affective symptoms in people with dementia: a 24-week cluster randomized controlled trial.
      Light therapy glasses contain LEDs and can be worn comfortably.
      • Comtet H.
      • Geoffroy P.A.
      • Kobayashi Frisk M.
      • et al.
      Light therapy with boxes or glasses to counteract effects of acute sleep deprivation.
      Thus, ambient light and light therapy glasses can be integrated into daily life.
      • Hjetland G.J.
      • Kolberg E.
      • Pallesen S.
      • et al.
      Ambient bright light treatment improved proxy-rated sleep but not sleep measured by actigraphy in nursing home patients with dementia: a placebo-controlled randomised trial.
      Residents can remain active during the therapy, continuing to perform tasks such as eating, reading, and walking.
      • Raymackers J.M.
      • Andrade M.
      • Baey E.
      • et al.
      Bright light therapy with a head-mounted device for anxiety, depression, sleepiness and fatigue in patients with Parkinson's disease.
      This translates to greater compliance with therapy than if fixed equipment were used. On the other hand, some residents may find light therapy glasses to be uncomfortable
      • Comtet H.
      • Geoffroy P.A.
      • Kobayashi Frisk M.
      • et al.
      Light therapy with boxes or glasses to counteract effects of acute sleep deprivation.
      and to induce headache, blurred vision, and visual discomfort. This may be in part because the light source is so close to the eyes.
      Using outdoor natural light for light therapy can provide even more flexibility for residents and may lead to less eye irritation, but this approach makes it difficult to control the actual daytime light intensity delivered. In addition, residents may become uncomfortable or experience health problems, such as high blood pressure, if they receive outdoor light therapy when the outside temperature is high.
      • Wahnschaffe A.
      • Nowozin C.
      • Rath A.
      • et al.
      Night-time activity forecast by season and weather in a longitudinal design - natural light effects on three years' rest-activity cycles in nursing home residents with dementia.
      The studies in this systematic review applied light therapy for different durations at different intensities. Short-term exposure (30-60 minutes) with high light levels (≥10,000 lux), relatively long-term exposure (1-2 hours) with moderate light levels (2500-10,000 lux), or long-term exposure (1-4 hours or full day) with low light levels (≤2500 lux) were associated with improved sleep indicators.
      • Kolberg E.
      • Hjetland G.J.
      • Thun E.
      • et al.
      The effects of bright light treatment on affective symptoms in people with dementia: a 24-week cluster randomized controlled trial.
      ,
      • Rutten S.
      • Vriend C.
      • Smit J.H.
      • et al.
      Bright light therapy for depression in Parkinson disease: a randomized controlled trial.
      ,
      • Konis K.
      • Mack W.J.
      • Schneider E.L.
      Pilot study to examine the effects of indoor daylight exposure on depression and other neuropsychiatric symptoms in people living with dementia in long-term care communities.
      For example, one study
      • Riemersma-van D.L.R.F.
      • Swaab D.F.
      • Twisk J.
      • et al.
      Effect of bright light and melatonin on cognitive and noncognitive function in elderly residents of group care facilities: a randomized controlled trial.
      found that full-day exposure to bright white light from a large number of fluorescent lamps in the ceiling (>1000 lux at the cornea) can improve sleep quality in patients with Alzheimer’s disease or related dementia. Another study found that spending 2.5 hours outdoors in natural light each morning improved sleep quality of older adults living in residential long-term care.
      • Burns A.C.
      • Saxena R.
      • Vetter C.
      • et al.
      Time spent in outdoor light is associated with mood, sleep, and circadian rhythm-related outcomes: a cross-sectional and longitudinal study in over 400,000 UK Biobank participants.
      Several studies
      • Akyar I.
      • Akdemir N.
      The effect of light therapy on the sleep quality of the elderly: an intervention study.
      ,
      • Fetveit A.
      • Bjorvatn B.
      Bright-light treatment reduces actigraphic measured daytime sleep in nursing home patients with dementia - A pilot study.
      ,
      • Fetveit A.
      • Bjorvatn B.
      The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.
      found improved sleep quality in older adults using a light box of 6000 to 10,000 lux for 30 minutes or 2 hours. On the other hand, one study
      • Zhang J.
      • Wu W.
      • Huang lc
      • et al.
      Effect of light therapy on circadian sleep disorder in the elderly.
      found no improvement in sleep interruption after exposure lasting 30 minutes a day 3 times a week.
      • Wu M.
      • Sung H.
      • Lee W.
      • et al.
      The effects of light therapy on depression and sleep disruption in older adults in a long-term care facility.
      These studies suggest that light can improve sleep in older adults in long-term care settings, but that the therapy needs to be optimized to ensure efficacy.
      Although 2500 lux appears in the literature as the accepted standard dose of light therapy, whether it is optimal for all users is not clear.
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      Such optimization should consider that older and younger individuals may not perceive the same dose of light in the same way because eyesight degrades with age.
      • Martin J.
      • Marler M.
      • Harker J.
      • et al.
      A multicomponent nonpharmacological intervention improves activity rhythms among nursing home residents with disrupted sleep/wake patterns.
      Most of the participants in our review (405 of 748) were older patients with dementia. Although several studies have demonstrated that light therapy can improve sleep disorders in older people with dementia,
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      ,
      • Figueiro M.G.
      • Plitnick B.A.
      • Lok A.
      • et al.
      Tailored lighting intervention improves measures of sleep, depression, and agitation in persons with Alzheimer's disease and related dementia living in long-term care facilities.
      ,
      • Van Someren E.J.
      • Kessler A.
      • Mirmiran M.
      • et al.
      Indirect bright light improves circadian rest-activity rhythm disturbances in demented patients.
      its efficacy may depend on the type and severity of dementia. For example, patients with mild and moderate Alzheimer’s disease may benefit more from bright light therapy than patients with severe dementia.
      • Kim S.J.
      • Lee S.H.
      • Suh I.B.
      • et al.
      Positive effect of timed blue-enriched white light on sleep and cognition in patients with mild and moderate Alzheimer's disease.
      ,
      • Sekiguchi H.
      • Iritani S.
      • Fujita K.
      Bright light therapy for sleep disturbance in dementia is most effective for mild to moderate Alzheimer's type dementia: a case series.
      It is possible that extensive loss of melanopsin retinal ganglion cells in patients with advanced Alzheimer’s disease may render them less sensitive to the synchronizing effects of light therapy.
      • Konis K.
      Field evaluation of the circadian stimulus potential of daylit and non-daylit spaces in dementia care facilities.
      Similarly, the type of dementia seems to have an impact on the effects of light therapy. For example, one study
      • Mishima K.
      • Hishikawa Y.
      • Okawa M.
      Randomized, dim light controlled, crossover test of morning bright light therapy for rest-activity rhythm disorders in patients with vascular dementia and dementia of Alzheimer's type.
      found that intense light treatment significantly improved sleep quality in patients with vascular dementia, but not in patients with Alzheimer’s disease. This may be due to the fact that in vascular dementia, lacunar infarctions lie predominantly in the subcortical area and may disconnect neural pathways leading to and from the suprachiasmatic nucleus, leading to sleep rhythm disorder.
      • Harper D.G.
      • Stopa E.G.
      • McKee A.C.
      • et al.
      Dementia severity and Lewy bodies affect circadian rhythms in Alzheimer disease.
      In contrast, Alzheimer‘s disease usually involves damage to the hippocampus and medial temporal lobe of the brain, which may lead to different responses to light therapy. Other studies have pointed out that light therapy can improve agitation behavior and emotional cognition in dementia.
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      ,
      • Cibeira N.
      • Maseda A.
      • Lorenzo-López L.
      • et al.
      Bright light therapy in older adults with moderate to very severe dementia: immediate effects on behavior, mood, and physiological parameters.
      ,
      • Burns A.
      • Allen H.
      • Tomenson B.
      • et al.
      Bright light therapy for agitation in dementia: a randomized controlled trial.
      Taken together, these studies of patients with dementia suggest that light therapy can be effective for improving sleep, but it may need to be tailored to the type and stage of dementia.
      In general, the literature on light therapy for residents in long-term care settings indicates low withdrawal rate and high compliance. Among the 21 included studies, six articles
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      ,
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      ,
      • Ancoli-Israel S.
      • Gehrman P.
      • Martin J.L.
      • et al.
      Increased light exposure consolidates sleep and strengthens circadian rhythms in severe Alzheimer's disease patients.
      ,
      • Wu M.
      • Sung H.
      • Lee W.
      • et al.
      The effects of light therapy on depression and sleep disruption in older adults in a long-term care facility.
      ,
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      ,
      • Linander C.B.
      • Kallemose T.
      • Joergensen L.M.
      • et al.
      The effect of circadian-adjusted LED-based lighting on sleep, daytime sleepiness and biomarkers of inflammation in a randomized controlled cross-over trial by pragmatic design in elderly care home dwellers.
      reported data on withdrawal from light therapy. In 5 studies,
      • Gasio P.F.
      • Krauchi K.
      • Cajochen C.
      • et al.
      Dawn-dusk simulation light therapy of disturbed circadian rest-activity cycles in demented elderly.
      ,
      • Wu M.
      • Sung H.
      • Lee W.
      • et al.
      The effects of light therapy on depression and sleep disruption in older adults in a long-term care facility.
      ,
      • Figueiro M.G.
      • Plitnick B.
      • Roohan C.
      • et al.
      Effects of a tailored lighting Intervention on sleep quality, rest-activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial.
      ,
      • Linander C.B.
      • Kallemose T.
      • Joergensen L.M.
      • et al.
      The effect of circadian-adjusted LED-based lighting on sleep, daytime sleepiness and biomarkers of inflammation in a randomized controlled cross-over trial by pragmatic design in elderly care home dwellers.
      ,
      • Fetveit A.
      • Skjerve A.
      • Bjorvatn B.
      Bright light treatment improves sleep in institutionalised elderly - an open trial.
      64 of 208 participants (30.8%) stopped participating in the trial, and the reasons were that (1) the participants could not begin the study because they had died or were hospitalized; (2) they did not comply with the study protocol, they refused to wear the Actigraph, or they were afraid of the dawn-dusk simulation; or (3) the therapy equipment failed. Other studies
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      ,
      • Juda M.
      • Liu-Ambrose T.
      • Feldman F.
      • et al.
      Light in the senior home: effects of dynamic and individual light exposure on sleep, cognition, and well-being.
      described participants who dropped out because of restlessness during light therapy.
      Few side effects of light therapy have been described in previous studies of older people, which suggests that serious side effects are rare.
      • Rutten S.
      • Vriend C.
      • Smit J.H.
      • et al.
      Bright light therapy for depression in Parkinson disease: a randomized controlled trial.
      ,
      • Rutten S.
      • Vriend C.
      • Smit J.H.
      • et al.
      A double-blind randomized controlled trial to assess the effect of bright light therapy on depression in patients with Parkinson's disease.
      This may reflect that some studies exclude participants who have proliferative diabetes retinopathy or moderate or severe maculopathy, or patients who lack natural or intraocular lenses in any eye.
      • Sloane P.D.
      • Williams C.S.
      • Mitchell C.M.
      • et al.
      High-intensity environmental light in dementia: effect on sleep and activity.
      ,
      • Hopkins S.
      • Morgan P.L.
      • Schlangen L.J.M.
      • et al.
      Blue-enriched lighting for older people living in care homes: effect on activity, actigraphic sleep, mood and alertness.
      These conditions may render individuals vulnerable to retinal damage from intense light. Our review identified 2 articles reporting possible side effects of light therapy. A participant in one study
      • Fetveit A.
      • Bjorvatn B.
      Bright-light treatment reduces actigraphic measured daytime sleep in nursing home patients with dementia - A pilot study.
      had temporary mild eye irritation 4-5 minutes after light therapy, but this gradually disappeared after a few days of treatment. One participant in another study
      • Skjerve A.
      • Holsten F.
      • Aarsland D.
      • et al.
      Improvement in behavioral symptoms and advance of activity acrophase after short-term bright light treatment in severe dementia.
      developed a marked increase in agitation and confusion during the second week of treatment. Nevertheless, a systematic review
      • Chang C.H.
      • Liu C.Y.
      • Chen S.J.
      • et al.
      Efficacy of light therapy on nonseasonal depression among elderly adults: a systematic review and meta-analysis.
      of 8 studies reported no obvious adverse reactions to light therapy, and no manic behavior during treatment or follow-up.
      • Fetveit A.
      • Skjerve A.
      • Bjorvatn B.
      Bright light treatment improves sleep in institutionalised elderly - an open trial.
      Thus, the literature suggests that light therapy is generally safe but that it may trigger side effects such as eye irritation or discomfort. The eye condition of participants should be carefully evaluated before light therapy, and participants should be monitored during therapy in order to detect adverse reactions.
      • Videnovic A.
      • Klerman E.B.
      • Wang W.
      • et al.
      Timed light therapy for sleep and daytime sleepiness associated with parkinson disease: a randomized clinical trial.
      Some of the studies included in this review reported that light therapy did not have a significant effect on sleep. This negative result could be related to short intervention time, small sample, and heterogeneity among patients, which may mask significant benefits for certain individuals. It could also reflect that light therapy was not delivered at an optimal time according to patients’ circadian rhythm, which affects how they perceive light environments. It may reflect confounding by comorbidities, age, and psychosocial factors.
      • Linander C.B.
      • Kallemose T.
      • Joergensen L.M.
      • et al.
      The effect of circadian-adjusted LED-based lighting on sleep, daytime sleepiness and biomarkers of inflammation in a randomized controlled cross-over trial by pragmatic design in elderly care home dwellers.
      A longitudinal study design may help reduce such confounding,
      • Juda M.
      • Liu-Ambrose T.
      • Feldman F.
      • et al.
      Light in the senior home: effects of dynamic and individual light exposure on sleep, cognition, and well-being.
      and longer interventions are needed to reliably observe changes on sleep.
      Many researchers have suggested that a combination of light therapy, melatonin supplements, exercise, and changes in the sleep environment may have a more robust effect on circadian rhythms and sleep patterns than light therapy alone. For example, one study reported significant improvements in daytime alertness, increased activity, and stability of activity-rest rhythms in older adults treated with a combination of light therapy and melatonin.
      • Cheng D.C.Y.
      • Ganner J.L.
      • Gordon C.J.
      • et al.
      The efficacy of combined bright light and melatonin therapies on sleep and circadian outcomes: a systematic review.
      Light therapy appears to mitigate the negative effects of melatonin on mood, but to what extent still needs to be evaluated. To avoid such side effects, it may be useful to combine light therapy with individualized exercise plans.
      • McCurry S.M.
      • Pike K.C.
      • Vitiello M.V.
      • et al.
      Increasing walking and bright light exposure to improve sleep in community-dwelling persons with Alzheimer's disease: results of a randomized, controlled trial.

      Implications

      Ensuring access to sufficient lighting is especially important for individuals in long-term care settings, yet indoor lighting in these settings is a neglected issue. Because increasing exposure to sunlight can improve the sleep of patients with Alzheimer's disease and related dementias,
      • Figueiro M.G.
      • Hamner R.
      • Higgins P.
      • et al.
      Field measurements of light exposures and circadian disruption in two populations of older adults.
      long-term care settings and other care facilities should be designed in such a way that older individuals receive more natural light as part of their daily activities.
      • Lucas R.J.
      • Peirson S.N.
      • Berson D.M.
      • et al.
      Measuring and using light in the melanopsin age.
      At the same time, long-term care settings can incorporate dynamic lighting systems that may improve the circadian rhythm of residents and thereby improve their sleep patterns.
      The myriad improvements in sleep outcomes from lighting interventions underscore the importance of lighting systems in health care settings, but the inconsistency in findings highlights the need for further research on these systems. Future research on light therapy should be more rigorous in how light exposure is measured and how indoor and outdoor lighting environments are assessed. Future studies should also include relatively large samples, longer interventions, and suitably longer follow-up, preferably with a randomized design. Rigorous procedures will be crucial for optimizing the various parameters of light therapy, including intensity, wavelength, duration, and timing.

      Limitations

      The 21 studies in our review applied recognized indicators and assessment instruments, but these varied substantially across the studies. In addition, the studies differed in the light therapy regimens and the clinic demographics of their samples. The studies measured sleep outcomes in a variety of ways, including actigraphy, salivary melatonin data, sleep diaries, and various sleep scales. Therefore, we were not able to meta-analyze the reported data, preventing a quantitative understanding of the efficacy of light therapy. Moreover, we did not exclude studies based on the study quality. Although this may help ensure a complete review of available evidence, the resulting heterogeneity may bring bias to the final results. For example, one article
      • Koyama E.
      • Matsubara H.
      • Nakano T.
      Bright light treatment for sleep-wake disturbances in aged individuals with dementia.
      in our review contained only 6 participants, so its findings may be less reliable and generalizable.

      Conclusions

      There is substantial evidence to show that light therapy can improve sleep quality in older people living in long-term care settings. This systematic review adds to the body of evidence that light therapy can be used as a supplement to drug therapy to improve sleep in older individuals living in long-term care settings.

      Supplementary Data

      Supplementary Table 1Search Strategies
      Group 1 Sleep Disorders
       (Sleep or "Sleep Wake Disorder
      Intercept character.
      " or "Sleep Disorder
      Intercept character.
      " or Dyssomnia
      Intercept character.
      or "Sleep Deprivation" or "Inadequate Sleep" or "Sleep Insufficien" or "Circadian Rhythm
      Intercept character.
      " or Sleepiness or Somnolence or Parasomnias or insomnia
      Intercept character.
      ) AND
      Group 2 Light and lighting
       (Phototherap
      Intercept character.
      OR "Light Therap
      Intercept character.
      " OR "light treatment" OR "bright light" OR "light exposure" OR sunlight OR "artifificial light" OR heliotherap
      Intercept character.
      ) AND
      Group 3 Long-term care facilities
       ("nursing home
      Intercept character.
      " OR "Residential Facilit
      Intercept character.
      " OR "Assisted Living Facilit
      Intercept character.
      " OR "Group Home
      Intercept character.
      " OR "Homes for the Aged
      Intercept character.
      " OR "Old Age Home
      Intercept character.
      " OR "Skilled Nursing Facilit
      Intercept character.
      " OR "Long-Term Care" OR Institutionalization
      Intercept character.
      OR "old age homes" OR "residential aged care" OR "rest homes" OR "care homes" OR "personal care homes" OR "institutional care
      Intercept character.
      ")
      Intercept character.

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        Journal of the American Medical Directors Association
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          Regarding the January 2023 article, Zhang M, et al. Light Therapy to Improve Sleep Quality in Older Adults Living in Residential Long-Term Care: A Systematic Review. J Am Med Dir Assoc 2023;24(1):65-74.
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