Area-level socioeconomic inequalities in mortality in China: a nationwide cohort study based on the ChinaHEART project

Abstract

Socioeconomic status is a key social determinant of health. Compared with individual-level socioeconomic status, the association between area-level socioeconomic status and mortality has not been well investigated in China. We aimed to assess associations between area-level socioeconomic status and all-cause mortality and cause-specific mortality in China, as well as the interplay of area-level and individual-level socioeconomic status on mortality. In this nationwide cohort study, residents aged 35-75 years from 453 districts and counties were included in the China Health Evaluation and Risk Reduction Through Nationwide Teamwork (ChinaHEART) Study. The composite value of area-level socioeconomic status was generated from national census data and categorised into tertiles. Mortality rates and their 95% CIs were calculated using the Clopper-Pearson method. Cox frailty models were fitted to calculate adjusted hazard ratios and 95% CIs for area-level socioeconomic status with the risk of all-cause mortality and cause-specific mortality and their disparities across different population. We also assessed the roles of multiple individual factors as potential mediators. Between December, 2015, and December, 2022, 1 119 027 participants were included, for whom the mean age was 56·1 (SD 9·9) years and 672 385 (60·1%) were female. 24 426 (5·24 [95% CI 5·18-5·31] per 1000 person-years) deaths occurred during the median 4·5-year follow-up. Compared with high area-level socioeconomic status, low area-level socioeconomic status was significantly associated with an increased risk of all-cause (hazard ratio 1·11, 95% CI 1·07-1·16), cardiovascular disease (1·38, 1·29-1·48), and respiratory disease (1·44, 1·22-1·71) mortality. The stronger associations were observed in people older than 60 years, females, and participants with lower individual-level socioeconomic status. The individual-level socioeconomic, behavioural, and metabolic factors mediated 39·5% of the association between area-level socioeconomic status and mortality, of which individual-level socioeconomic status made the largest contribution. There are substantial area-level socioeconomic status-related inequalities in mortality in China. Individual-level socioeconomic, behavioural, and metabolic factors had mediating effects. Actions to improve area-level circumstances and individual factors are needed to improve health equity. The Chinese Academy of Medical Sciences Innovation Fund for Medical Science, the National High Level Hospital Clinical Research Funding, the Ministry of Finance of China, and the National Health Commission of China. For the Chinese translation of the abstract see Supplementary Materials section.