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Associations Between Social Isolation and Physical Frailty in Older Adults: A Systematic Review and Meta-Analysis

      To the Editor:
      The emergence of COVID-19 has drastically changed our daily lives.
      • Yu J.
      • Mahendran R.
      COVID-19 lockdown has altered the dynamics between affective symptoms and social isolation among older adults: Results from a longitudinal network analysis.
      Lockdowns were imposed across many countries for extended periods of time during the pandemic to reduce the risk of infection.
      • Yu J.
      • Mahendran R.
      COVID-19 lockdown has altered the dynamics between affective symptoms and social isolation among older adults: Results from a longitudinal network analysis.
      However, the side effects of lockdowns included loss of opportunities to socialize and interact with other people. Social isolation and its impacts on health have since been highlighted, especially among high-risk populations of older people.
      • Yu J.
      • Mahendran R.
      COVID-19 lockdown has altered the dynamics between affective symptoms and social isolation among older adults: Results from a longitudinal network analysis.
      Social isolation has been well documented as a significant risk factor of mortality, and has also been shown to be associated with poorer physical and mental health.
      • Holt-Lunstad J.
      • Smith T.B.
      • Baker M.
      • et al.
      Loneliness and social isolation as risk factors for mortality: A meta-analytic review.
      Frailty is a geriatric syndrome characterized by cumulative age-related health deficits, decreased physiological reserve, and increased vulnerability to stressors.
      • Clegg A.
      • Young J.
      • Iliffe S.
      • et al.
      Frailty in elderly people.
      ,
      • Kojima G.
      • Liljas A.E.M.
      • Iliffe S.
      Frailty syndrome: implications and challenges for health care policy.
      Although social isolation and frailty are common in older adults, evidence is limited in the literature regarding the associations between social isolation and frailty.
      • Mehrabi F.
      • Béland F.
      Effects of social isolation, loneliness and frailty on health outcomes and their possible mediators and moderators in community-dwelling older adults: A scoping review.
      The aim of this systematic review and meta-analysis was to investigate the associations between social isolation and frailty in community-dwelling older adults.

      Methods

      Search Strategy and Study Selection

      The protocol was developed according to the PRISMA statements. PubMed was searched in March 2022 without language restriction for longitudinal and cross-sectional observational studies published in 2000 or later providing associations between social isolation and physical frailty. The populations included community-dwelling older adults with a mean age of 60 or older. The search strategy used the Medical Subject Heading (MeSH) and text terms: “social isolation (MeSH)” OR “social isolation” OR “socially isolated” OR “Berkman-syme” OR “Lubben” OR “disconnectedness” AND “frailty (MeSH)” OR “frailty” OR “frailties” OR “frail elderly (MeSH)” OR “frail elderly”. Reference lists of relevant articles were also searched. It was attempted to contact study authors for necessary data. Risks of bias were examined using the 8-item Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross-Sectional Studies (https://jbi.global/sites/default/files/2019-05/JBI_Critical_Appraisal-Checklist_for_Analytical_Cross_Sectional_Studies2017_0.pdf) and were considered to be low if the score was ≥4 of 8. Odds ratios (ORs) of social isolation and frailty were combined using fixed-effects meta-analysis. Publication bias was examined by visually inspecting a funnel plot. Data analyses were performed using Review Manager 5 (The Cochrane Collaboration, Copenhagen, Denmark).

      Results

      Among 317 citations identified by the systematic review, 5 cross-sectional studies and 4 longitudinal studies were included in this review (Supplementary Table 1). A fix-effect meta-analysis combining ORs from 3 cross-sectional studies
      • Hoogendijk E.O.
      • Smit A.P.
      • van Dam C.
      • et al.
      Frailty combined with loneliness or social isolation: An elevated risk for mortality in later life.
      • Merchant R.A.
      • Liu S.G.
      • Lim J.Y.
      • et al.
      Factors associated with social isolation in community-dwelling older adults: A cross-sectional study.
      • Cudjoe T.K.M.
      • Selvakumar S.
      • Chung S.E.
      • et al.
      Getting under the skin: social isolation and biological markers in the National Health and Aging Trends Study.
      showed significant association between social isolation and frailty (3 studies: pooled OR = 1.88; 95% confidence interval = 1.60–2.20; P < .001) (Figure 1). All 3 studies were considered to have low risk of bias (all studies scored 8 of 8). Heterogeneity was low (I2 = 21%; P = .28). It was difficult to assess the funnel plot because of the limited number of the included studies. Longitudinal studies examining associations between social isolation used different statistical methodologies; therefore, they could not be combined by meta-analysis. These studies showed mixed results, most of which did not reach statistical significance.
      Figure thumbnail gr1
      Fig. 1Forest plot of ORs of cross-sectional association between social isolation and frailty.

      Discussion

      The current review and meta-analysis pooling data from 3 cross-sectional studies suggests that socially isolated older adults are significantly more likely to be frail compared with their counterparts.
      There is little evidence on longitudinal associations between social isolation and frailty,
      National Academies of Sciences, Engineering, and Medicine
      Social Isolation and Loneliness in Older Adults: Opportunities for the Health Care System.
      and how these 2 entities are associated is not known. One study of 2346 older adults in England showed that only men with high social isolation level had an increased risk of becoming frail.
      • Gale C.R.
      • Westbury L.
      • Cooper C.
      Social isolation and loneliness as risk factors for the progression of frailty: The English Longitudinal Study of Ageing.
      Although we could not find previous studies that investigated if baseline frailty may contribute to the development of social isolation, it may be plausible to consider the direction of the pathway. Frail older people tend to have impaired physical functions,
      • Clegg A.
      • Young J.
      • Iliffe S.
      • et al.
      Frailty in elderly people.
      such as slow gait speed or difficulty in activities of daily living, which may limit interaction and socialization with others, increasing risk of social isolation.
      National Academies of Sciences, Engineering, and Medicine
      Social Isolation and Loneliness in Older Adults: Opportunities for the Health Care System.
      Strengths of this study include the use of comprehensive methodology following the PRISMA statements, search strategy using the MeSH and text terms, identification of a study from another source, screening by 2 investigators, assessment of risk of bias, heterogeneity, publication bias, and successful performance of a meta-analysis to provide pooled evidence. As for limitations, a small number of studies were used for the meta-analysis, which hinders sensitivity, and subgroup and meta-regression analyses. It was not possible to combine results of longitudinal studies due to different methodologies; therefore, the directionality cannot be inferred. All ORs used for the meta-analysis were not adjusted for important confounders.
      This is the first pooled evidence of significant cross-sectional association between social isolation and frailty in community-dwelling older adults. More research, especially longitudinal studies, is clearly needed to enable the enhancement of our understanding of the underlying mechanisms and pathophysiology of social isolation and frailty.

      Author Contributions

      Study concept and design: GK, RA, and MT. Analysis and interpretation of data: GK, RA, and MT. Drafting the article: GK. Revising the article critically for important intellectual content: GK, RA, and MT. Final approval of the version to be published: GK, RA, and MT.

      Acknowledgments

      The contents do not necessarily represent the views of the Department of Veterans Affairs or the U.S. government.

      Supplementary Data

      Supplementary Table 1Summary of Included Studies on Social Isolation and Frailty
      Author/Year/Study NameLocationSample SizeFemale, %Age (Range)Social Isolation MeasuresFrailty CriteriaStudy Design (Follow-up)Findings
      Cross-sectional studies
       Mulasso 2016
      • Mulasso A.
      • Roppolo M.
      • Giannotta F.
      • et al.
      Associations of frailty and psychosocial factors with autonomy in daily activities: a cross-sectional study in Italian community-dwelling older adults.


      Act on Ageing
      Italy21066.273.4 (≥65)Friendship Scale (0–24)mCHSCS
      • -
        Mean score ± SD for robust, prefrail, and frail participants were 19.82 ± 4.21, 18.25 ± 4.55, and 16.45 ± 4.50
       Hayashi 2020
      • Hayashi T.
      • Umegaki H.
      • Makino T.
      • et al.
      Combined impact of physical frailty and social isolation on rate of falls in older adults.
      Japan38047.972.3 (-)LSNS-6 (0–30) (SI = 0–12)mCHSCS

        Unadjusted logistic regression model

      • -
        cOR = 1.50 (0.91–2.47) of SI for being frail/prefrail (ref: robust)
       Hoogendijk 2020
      • Hoogendijk E.O.
      • Smit A.P.
      • van Dam C.
      • et al.
      Frailty combined with loneliness or social isolation: an elevated risk for mortality in later life.


      LASA
      Netherlands142757.375.5 (≥65)Original scale (0–3) (SI = 2–3)mCHSCS

        Unadjusted logistic regression model

      • -
        cOR = 1.86 (1.34–2.58) of SI for being frail (ref: nonfrailty)
       Merchant 2020
      • Merchant R.A.
      • Liu S.G.
      • Lim J.Y.
      • et al.
      Factors associated with social isolation in community-dwelling older adults: a cross-sectional study.
      Singapore20278.274.1 (≥60)LSNS-6 (0–30) (SI = 0–12)FRAILCS

        Unadjusted logistic regression model

      • -
        cOR = 1.16 (0.62–2.16) of SI for being frail (ref: nonfrailty)
      • -
        cOR = 2.33 (0.61–8.89) of SI for being frail (ref: robust)
      • -
        cOR = 1.10 (0.59–2.06) of SI for being prefrail (ref: robust)
       Cudjoe 2021
      • Cudjoe T.K.M.
      • Selvakumar S.
      • Chung S.E.
      • et al.
      Getting under the skin: social isolation and biological markers in the national health and aging trends study.


      NHATS
      USA464855.476.0 (≥65)Berkman-Syme Social Network Index (SI = 1 or higher)mCHSCS

        Unadjusted logistic regression model

      • -
        cOR = 1.97 (1.63–2.39) of SI for being frail (ref: nonfrailty)
      • -
        cOR = 2.45 (1.98–3.03) of SI for being frail (ref: robust)
      • -
        cOR = 1.64 (1.34–2.01) of SI for being prefrail (ref: robust)
      Longitudinal studies
       Gale 2018
      • Gale C.R.
      • Westbury L.
      • Cooper C.
      • et al.
      Social isolation and loneliness as risk factors for the progression of frailty: the English Longitudinal Study of Ageing.


      ELSA
      UK234656.969.3 (≥60)Original scale (0–5)mCHSLT (4 y)

        Multinomial logistic regression models of baseline loneliness for worsening frailty (ref: low social isolation, robust)

      • -
        aOR = 0.92 (0.73–1.15) of average SI for prefrailty
      • -
        aOR = 0.88 (0.57–1.36) of average SI for frailty
      • -
        aOR = 1.19 (0.93–1.53) of high SI for prefrailty
      • -
        aOR = 1.12 (0.70–1.78) of high SI for frailty
       Jarach 2021
      • Jarach C.M.
      • Tettamanti M.
      • Nobili A.
      • et al.
      Social isolation and loneliness as related to progression and reversion of frailty in the Survey of Health Aging Retirement in Europe (SHARE).


      SHARE
      European countries
      Sweden, Denmark, Austria, Germany, France, Switzerland, Belgium, Luxembourg, Czech Republic, Slovenia, Spain, Italy, and Israel.
      27,46854.670.5 (≥60)Original scale (0–3)mCHSLT (2 years)Multinomial logistic regression models of baseline

        SI for frailty change (
        P < .05.
        P < .05)

      • -
        aOR = 1.17 of average SI for robust to prefrail
        P < .05.
      • -
        aOR = 1.84 of average SI for robust to frail
        P < .05.
      • -
        aOR = 1.62 of average SI for prefrail to frail
        P < .05.
      • -
        aOR = 0.93 of average SI for prefrail to robust
      • -
        aOR = 0.84 of average SI for frail to prefrail
      • -
        aOR = 1.14 of average SI for frail to robust
      • -
        aOR = 1.35 of high SI for robust to prefrail
        P < .05.
      • -
        aOR = 2.06 of high SI for robust to frail
        P < .05.
      • -
        aOR = 1.90 of high SI for prefrail to frail
        P < .05.
      • -
        aOR = 0.89 of high SI for prefrail to robust
      • -
        aOR = 0.96 of high SI for frail to prefrail
      • -
        aOR = 0.82 of high SI for frail to robust
       Uno 2021
      • Uno C.
      • Okada K.
      • Matsushita E.
      • et al.
      Friendship-related social isolation is a potential risk factor for the transition from robust to prefrailty among healthy older adults: a 1-year follow-up study.
      Japan22953.769.3 (≥60)LSNS-6 family (0–15) (family SI = 0–6)

      LSNS-6 friend (0–15) (friend SI = 0–6)
      mCHSLT (1 year)
      • -
        aOR = 0.61 (0.23–1.63) of family SI for incident prefrailty
      • -
        aOR = 4.58 (2.11–9.92) of friend SI for incident prefrailty
       Ge 2022
      • Ge L.
      • Yap C.W.
      • Heng B.H.
      • et al.
      Associations of social isolation, social participation, and loneliness with frailty in older adults in Singapore: a panel data analysis.


      PHI Survey
      Singapore60657.670.1 (≥60)LSNS-6 family subscale and friends subscaleCFS
      CFS as a 7-level ordered variable.
      LT (3 years)Fixed-effects ordinal logistic regression of baseline

        SI for worsening frailty

      • -
        aOR = 1.05 (0.97–1.14), P = .231 for LSNS-6

        Family

      • -
        aOR = 0.99 (0.92–1.07), P = .782 for LSNS-6
      Friends
      aOR, adjusted odds ratio; CFS, Clinical Frailty Scale; cOR, calculated odds ratio; CS, cross-sectional study design; ELSA, English Longitudinal Study of Ageing; LSNS-6, 6-item Lubben Social Network Scale; LT, longitudinal study design; mCHS, Modified Cardiovascular Health Study criteria; NHATS, National Health and Aging Trends Study; PHI Survey, Population Health Index Survey; SI, social isolation.
      Sweden, Denmark, Austria, Germany, France, Switzerland, Belgium, Luxembourg, Czech Republic, Slovenia, Spain, Italy, and Israel.
      P < .05.
      CFS as a 7-level ordered variable.

      References

        • Yu J.
        • Mahendran R.
        COVID-19 lockdown has altered the dynamics between affective symptoms and social isolation among older adults: Results from a longitudinal network analysis.
        Sci Rep. 2021; 11: 14739
        • Holt-Lunstad J.
        • Smith T.B.
        • Baker M.
        • et al.
        Loneliness and social isolation as risk factors for mortality: A meta-analytic review.
        Perspect Psychol Sci. 2015; 10: 227-237
        • Clegg A.
        • Young J.
        • Iliffe S.
        • et al.
        Frailty in elderly people.
        Lancet. 2013; 381: 752-762
        • Kojima G.
        • Liljas A.E.M.
        • Iliffe S.
        Frailty syndrome: implications and challenges for health care policy.
        Risk Manag Healthc Policy. 2019; 12: 23-30
        • Mehrabi F.
        • Béland F.
        Effects of social isolation, loneliness and frailty on health outcomes and their possible mediators and moderators in community-dwelling older adults: A scoping review.
        Arch Gerontol Geriatr. 2020; 90: 104119
        • Hoogendijk E.O.
        • Smit A.P.
        • van Dam C.
        • et al.
        Frailty combined with loneliness or social isolation: An elevated risk for mortality in later life.
        J Am Geriatr Soc. 2020; 68: 2587-2593
        • Merchant R.A.
        • Liu S.G.
        • Lim J.Y.
        • et al.
        Factors associated with social isolation in community-dwelling older adults: A cross-sectional study.
        Qual Life Res. 2020; 29: 2375-2381
        • Cudjoe T.K.M.
        • Selvakumar S.
        • Chung S.E.
        • et al.
        Getting under the skin: social isolation and biological markers in the National Health and Aging Trends Study.
        J Am Geriatr Soc. 2022; 70: 408-414
        • National Academies of Sciences, Engineering, and Medicine
        Social Isolation and Loneliness in Older Adults: Opportunities for the Health Care System.
        National Academies Press, 2020
        • Gale C.R.
        • Westbury L.
        • Cooper C.
        Social isolation and loneliness as risk factors for the progression of frailty: The English Longitudinal Study of Ageing.
        Age Ageing. 2018; 47: 392-397

      Further readings

        • Mulasso A.
        • Roppolo M.
        • Giannotta F.
        • et al.
        Associations of frailty and psychosocial factors with autonomy in daily activities: a cross-sectional study in Italian community-dwelling older adults.
        Clin Interv Aging. 2016; 11: 37-45
        • Hayashi T.
        • Umegaki H.
        • Makino T.
        • et al.
        Combined impact of physical frailty and social isolation on rate of falls in older adults.
        J Nutr Health Aging. 2020; 24: 312-318
        • Hoogendijk E.O.
        • Smit A.P.
        • van Dam C.
        • et al.
        Frailty combined with loneliness or social isolation: an elevated risk for mortality in later life.
        J Am Geriatr Soc. 2020; 68: 2587-2593
        • Merchant R.A.
        • Liu S.G.
        • Lim J.Y.
        • et al.
        Factors associated with social isolation in community-dwelling older adults: a cross-sectional study.
        Qual Life Res. 2020; 29: 2375-2381
        • Cudjoe T.K.M.
        • Selvakumar S.
        • Chung S.E.
        • et al.
        Getting under the skin: social isolation and biological markers in the national health and aging trends study.
        J Am Geriatr Soc. 2022; 70: 408-412
        • Gale C.R.
        • Westbury L.
        • Cooper C.
        • et al.
        Social isolation and loneliness as risk factors for the progression of frailty: the English Longitudinal Study of Ageing.
        Age Ageing. 2018; 47: 392-397
        • Jarach C.M.
        • Tettamanti M.
        • Nobili A.
        • et al.
        Social isolation and loneliness as related to progression and reversion of frailty in the Survey of Health Aging Retirement in Europe (SHARE).
        Age Ageing. 2021; 50: 258-262
        • Uno C.
        • Okada K.
        • Matsushita E.
        • et al.
        Friendship-related social isolation is a potential risk factor for the transition from robust to prefrailty among healthy older adults: a 1-year follow-up study.
        Eur Geriatr Med. 2021; 12: 285-293
        • Ge L.
        • Yap C.W.
        • Heng B.H.
        • et al.
        Associations of social isolation, social participation, and loneliness with frailty in older adults in Singapore: a panel data analysis.
        BMC Geriatr. 2022; 22: 26