Association between insomnia symptoms and social frailty in community-dwelling adults aged 75 years and older: a cross-sectional study

Insomnia has been associated with frailty; however, its association with social frailty remains unclear, particularly among adults aged 75 years and older. This study aimed to examine the association between insomnia symptoms and social frailty in community-dwelling adults aged 75 years and older. In this cross-sectional study, mailed questionnaire data were obtained from 2091 community-dwelling adults aged 75 years and older in Matsubara, Japan. Insomnia symptoms were assessed using the Japanese version of the Athens Insomnia Scale (AIS-J), with scores of ≥ 6 indicating insomnia symptoms. Social frailty was defined as a score of ≥ 2 on Makizako’s five-item questionnaire. Multivariable logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), with adjustment for sociodemographic factors and cognitive impairment in the primary model; an additional model further adjusted for physical frailty. Among participants with complete data on both AIS-J and social frailty, social frailty was present in 64.4% of those with insomnia symptoms and in 40.0% of those without insomnia symptoms. Insomnia symptoms were significantly associated with social frailty in the primary model adjusted for sociodemographic factors and cognitive impairment (OR, 2.35; 95% CI, 1.91–2.88). This association remained significant after further adjustment for physical frailty (OR, 1.93; 95% CI, 1.56–2.40). Insomnia symptoms were significantly associated with social frailty in community-dwelling adults aged 75 years and older. These findings underscore the relevance of sleep to social vulnerability in late old age, although longitudinal studies are needed to clarify directionality.