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Mental Health Center, West China Hospital, Sichuan University, Chengdu, Sichuan, ChinaSichuan Clinical Medical Research Center for Mental Disorders, Chengdu, Sichuan, China
Address correspondence to Zhenzhen Xiong, PhD, School of Nursing, Chengdu Medical College, No. 601 Tian Hui Road, Rong Du Avenue, Chengdu, Sichuan 610083, China; or Dan Zhao, MD, School of Nursing, Chengdu Medical College, No. 601 Tian Hui Road, Rong Du Avenue, Chengdu, Sichuan 610083, China.
Address correspondence to Zhenzhen Xiong, PhD, School of Nursing, Chengdu Medical College, No. 601 Tian Hui Road, Rong Du Avenue, Chengdu, Sichuan 610083, China; or Dan Zhao, MD, School of Nursing, Chengdu Medical College, No. 601 Tian Hui Road, Rong Du Avenue, Chengdu, Sichuan 610083, China.
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.
Sleep disorders are frequently observed in the older adult population. However, they can have serious effects on quality of life and aggravate existing diseases.
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.
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.
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.
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.
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.
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,
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.
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.
Light therapy has been widely applied as a convenient, safe, nondrug therapy against sleep disorders through its ability to modulate circadian rhythms.
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.
The effect of bright light therapy on sleep and circadian rhythms in renal transplant recipients: a pilot randomized, multicentre wait-list controlled trial.
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.
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.
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
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.
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.
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 Confounding
Bias in Selection of Participants Into the Study
Bias in Classification of Interventions
Bias Due to Deviations From Intended Interventions
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 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.
Fig. 1PRISMA flow diagram of study inclusion. CNKI, China National Knowledge Infrastructure; CBM, Chinese Biomedical Literature Database; VIP, China Science and Technology Journal Database.
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 Year
Study Design
Participants
Intervention
Duration and Frequency of Intervention; Follow-Up (If Any)
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.
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.
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.
Older 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)
Older 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
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.
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,
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.
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.
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.
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.
Interstudy differences in outcome measures made it impossible to compare efficacy directly across light therapy methods. Studies using stationary light-emitting devices reported efficacy.
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.
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.
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.
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.
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.
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
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.
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.
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,
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,
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
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
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.
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.
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
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
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,
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 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
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
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
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.
J Gerontol B Psychol Sci Soc Sci.2002; 57: S69-S78
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.
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
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.
: 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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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,
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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
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.
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
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
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.
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.
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.
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.
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.
Increasing walking and bright light exposure to improve sleep in community-dwelling persons with Alzheimer's disease: results of a randomized, controlled trial.
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,
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.
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
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.
The effect of bright light therapy on sleep and circadian rhythms in renal transplant recipients: a pilot randomized, multicentre wait-list controlled trial.
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.
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.
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.
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 Therapeutic Environment Screening Survey for Nursing Homes (TESS-NH): an observational instrument for assessing the physical environment of institutional settings for persons with dementia.
J Gerontol B Psychol Sci Soc Sci.2002; 57: S69-S78
Study protocol: cost-effectiveness of multidisciplinary nutritional support for undernutrition in older adults in nursing home and home-care: cluster randomized controlled trial.
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.
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.
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.
Effect of bright light and melatonin on cognitive and noncognitive function in elderly residents of group care facilities: a randomized controlled trial.
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.
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.
Increasing walking and bright light exposure to improve sleep in community-dwelling persons with Alzheimer's disease: results of a randomized, controlled trial.
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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