The effect of healthy lifestyles and social determinants on independent life expectancy and sex differences in China: evidence from a 13-year cohort study

BACKGROUND: Functional independence is the basis for healthy ageing and quality of late life. However, evidence on how healthy lifestyle factors and social determinants of health affect longevity in independence remains limited, particularly regarding sex differences. We aimed to examine the associations of these factors with life expectancy with and without dependency, and to assess whether such effects differ by sex. METHODS: This cohort study used data from the nationally representative Chinese Longitudinal Healthy Longevity Study (CLHLS), which collected data from 2008 to 2021. Participants aged 65-100 years were included if they had at least one follow-up or death record. Healthy lifestyle factors (ie, diet, physical activity, smoking, and alcohol use) and social determinants of health (ie, financial status, education, health-care access, built environment, and social context) were assessed at baseline. Functional independence was determined by self-reported need for assistance with activities of daily living and instrumental activities of daily living at each survey wave. A continuous-time three-state Markov model was applied to estimate hazard ratios and 95% CIs between independence, dependence, and death, yielding total and independent life expectancy by sex, adjusted for covariates. FINDINGS: 11 804 participants were included in the study. At age 65 years, females had longer total life expectancy than males (18·18 years [95% CI 17·74-18·49] vs 15·50 years [15·10-15·89]) but shorter independent life expectancy (10·35 years [10·13-10·55] vs 11·29 years [11·05-11·54]). The gain in independent life expectancy was greater for males with 3-4 healthy lifestyle factors versus males with 0-1 healthy lifestyle factors (2·45 years [2·24-2·67]) compared with females with 3-4 healthy lifestyle factors versus females with 0-1 healthy lifestyle factors (2·09 years [1·90-2·29], p=0·015). However, females had greater gains in independent life expectancy from favourable social determinants of health. Those with 4-5 positive social determinants of health indicators lived 1·95 (1·74-2·16) more years independently compared with those with 0-1, surpassing the 1·67 year (1·49-1·85) gain observed in males (p=0·047). The combination of both favourable lifestyle behaviours and supportive social conditions produced the largest improvement in independent life expectancy, with gains of 3·94 (3·73-4·15) years for males and 3·89 (3·68-4·11) years for females. INTERPRETATION: Pathways to healthy ageing differ between sexes in China: males benefit more from lifestyle modifications whereas females gain more from improved social conditions. These results underscore the importance of sex-specific public health strategies that focus on reducing unhealthy behaviours among males and improving social support for females. FUNDING: National Natural Science Foundation of China and Chinese Academy of Medical Sciences Innovation Fund. TRANSLATION: For the Chinese translation of the abstract see Supplementary Materials section.