Social isolation is a pervasive and debilitating condition that has adverse prognostic impacts. This condition often co-occurs with other geriatric syndromes, further exacerbating negative health outcomes. Given these considerations, the present study aims to elucidate the roles of social isolation in older adults with anorexia of aging and/or sarcopenia with respect to long-term mortality using a nationally representative cohort study.

Data were obtained from the Taiwan Longitudinal Study on Aging (TLSA), with a sample size of 3,762 study participants aged 50 years and older. Data from 1999 (wave 4) to 2015 (wave 9) were analyzed. The TLSA questionnaire was used to define social isolation, anorexia, and sarcopenia. Logistic regressions were employed to explore the associations between social isolation, anorexia, and sarcopenia. The Cox proportional hazard model was utilized to examine the synergistic effects of social isolation and anorexia or sarcopenia on 16-year all-cause mortality.

After controlling for demographic information and comorbidities, older adults with social isolation were significantly associated with anorexia (adjusted odds ratio [aOR] 1.46 [95% confidence interval: 1.00–2.12, p=0.0475]) and sarcopenia (aOR 1.35 [95% CI: 1.12–1.64, p=0.0021]). Furthermore, the synergistic effects of social isolation with anorexia (aOR 1.65 [95% CI: 1.25–2.18, p=0.0004]) or sarcopenia (aOR 1.65 [95% CI: 1.42–1.92, p<0.0001]) were both significantly associated with higher risks of all-cause mortality, while social isolation alone revealed borderline statistical significance.

Our findings indicate that social isolation is closely linked to anorexia and sarcopenia among middle-aged and older adults. Additionally, social isolation significantly exacerbates the long-term mortality risk associated with anorexia of aging and sarcopenia. However, social isolation alone appears to have borderline long-term mortality risk in this cohort. These findings underscore the importance of addressing social isolation in older adults with anorexia and/or sarcopenia to optimize their health outcomes and mitigate long-term mortality risk.