Overall lifestyles and socioeconomic inequity in mortality and life expectancy in China: the China health and nutrition survey.

Background: socioeconomic inequity in mortality and life expectancy remains inconclusive in low- and middle-income countries, and to what extent the associations are mediated or modified by lifestyles remains debatable.

Methods: we included 21,133 adults from China Health and Nutrition Survey (1991-2011) and constructed three parameters to reflect participants' overall individual- (synthesising income, education and occupation) and area-level (urbanisation index) socioeconomic status (SES) and lifestyles (counting the number of smoking, physical inactivity and unhealthy diet and bodyweight). HRs for mortality and life expectancy were estimated by time-dependent Cox model and life table method, respectively.

Results: during a median follow-up of 15.2 years, 1,352 deaths were recorded. HRs (95% CIs) for mortality comparing low versus high individual- and area-level SES were 2.38 (1.75-3.24) and 1.84 (1.51-2.24), respectively, corresponding to 5.7 (2.7-8.6) and 5.0 (3.6-6.3) life-year lost at age 50. Lifestyles explained ≤11.5% of socioeconomic disparity in mortality. Higher lifestyle risk scores were associated with higher mortality across all socioeconomic groups. HR (95% CI) for mortality comparing adults with low individual-level SES and 3-4 lifestyle risk factors versus those with high SES and 0-1 lifestyle risk factors was 7.06 (3.47-14.36), corresponding to 19.1 (2.6-35.7) life-year lost at age 50.

Conclusion: this is the first nationwide cohort study reporting that disadvantaged SES was associated with higher mortality and shorter life expectancy in China, which was slightly mediated by lifestyles. Risk lifestyles were related to higher mortality across all socioeconomic groups, and those with risk lifestyles and disadvantaged SES had much higher mortality risks.