Social isolation, loneliness, and functional disability in Chinese older women and men: a longitudinal cross-lag analysis

In this study, we explored the relationship between social isolation, loneliness, and functional impairment in 50-year-old participants, by sex. Using longitudinal data from the China Health and Retirement Longitudinal Study (2018 and 2020), 6,524 participants meeting the inclusion criteria were analyzed. A cross-lag model was established to explore the associations between social isolation, loneliness, activities of daily living (ADL), and instrumental ADL (IADL) disability over time, with results stratified by sex. Social isolation was not significantly associated with ADL and IADL disability, but loneliness was. Autoregressive associations indicated that social isolation, loneliness, and functional disability in 2018 predicted their exacerbations in 2020 (p < 0.001). Cross-lag analysis showed that the time-lagged effect of loneliness on ADL disability was greater in women (β = 0.27) than in men (β = 0.06); the time-lagged effect of ADL disability on loneliness was greater in men (β = 0.16) than in women (β = 0.05). The bidirectional time-lagged effects of loneliness and IADL disability showed opposite patterns between the sexes. Functional disability in China was significantly associated with loneliness but not with social isolation. Sex differences were observed in the time-lagged effect of loneliness on functional disability. These findings extend our understanding of the association between social relationships and functional disability in non-Western populations.