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

Background 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. Methods 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. Findings Between December, 2015, and December, 2022, 1 119 027 participants were included, for whom the mean age was 56<middle dot>1 (SD 9<middle dot>9) years and 672 385 (60<middle dot>1%) were female. 24 426 (5<middle dot>24 [95% CI 5<middle dot>18-5<middle dot>31] per 1000 person-years) deaths occurred during the median 4<middle dot>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<middle dot>11, 95% CI 1<middle dot>07-1<middle dot>16), cardiovascular disease (1<middle dot>38, 1<middle dot>29-1<middle dot>48), and respiratory disease (1<middle dot>44, 1<middle dot>22-1<middle dot>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<middle dot>5% of the association between area-level socioeconomic status and mortality, of which individual-level socioeconomic status made the largest contribution. Interpretation 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. Copyright (c) 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license.