Social isolation, socioeconomic status, and development of functional impairments in Chinese older adults aged 70 years and over: a cohort study

Background Social isolation in older people has been increasingly regarded as a public health issue in the face of rapid population ageing. It is not clear whether social isolation mediates the relationship between socioeconomic status and functional impairment. Methods We used data from a cohort of Chinese older people aged 70 or older living in community (n = 1590). Socioeconomic status (SES) was operationalised as highest education attainment, monthly income at baseline and longest held occupation in lifetime. Functional abilities were measured using Barthel's Index for activities of daily living (ADL) measured at 18 and 36 months of follow-up, from which impairment was defined as score <= 19. Social isolation was measured by six attributes, such as marital status, living alone, and social contact with others. A score of >= 3 was defined as being in social isolation. Causal mediation analysis using natural effect models was used to assess mediation by social isolation. Results We found that lower monthly income at baseline was related to higher risk of social isolation [relative risk comparing lowest to highest income (RR) = 1.52, 95% confidence interval (95% CI) 1.01-2.28]. Social gradient of ADL impairment was not clearly present. The evidence for the mediating role of social isolation was not clear. Conclusions Older people with low SES, particularly those with lower income, were at greater risk of social isolation. Policymakers should strive to improve the current community services and pension scheme to mitigate the situation of social isolation in older people in Hong Kong.