BackgroundBy the end of 2016, China was a country of about 230 million elderly individuals aged 60 years or more. Maintaining mental health has crucial roles in healthy ageing. Previously, we estimated that about 37% of Chinese individuals aged 45 years or more had depressive symptoms. In this study, we aimed to further assess the longitudinal associations between healthy lifestyles and depressive symptoms among the Chinese population. MethodsWe used the data from the Chinese Health and Retirement Longitudinal Study, which were recorded in 2011–12, 2013–14, and 2015–16. We included data from individuals aged 45 years or more. Depressive symptoms were defined according to the ten-item Center for Epidemiologic Studies-Depression Scale. Lifestyles were defined by participation in social activities (11 items), smoking status, drinking status, and duration of sleep at night. The primary outcome was the longitudinal associations between lifestyles and depressive symptoms. We did this analysis using generalised estimating equations, adjusting for confounders including age group (45–59 years, 60–74 years, and ≥75 years), sex, urban or rural, socioeconomic factors, underlying conditions, and family death that occurred in the past 2 years. Ethical approval for this study was granted by the Ethical Review Committee of Peking University. We obtained written informed consent from all participants. FindingsFrom 2011–12 to 2015–16, 13 256 individuals were included in our analysis, contributing to a total of 34 523 observations. The overall prevalence of depressive symptoms was 37·0% (4369 of 11 802) in 2011–12, decreasing to 31·7% (3641 of 11 477) in 2013–14 and then increasing to 34·6% (3891 of 11 244) in 2015–16 (p<0·0001). Similar trends were observed for each age group, sex, urban or rural residents, and participants with underlying conditions. Engagement in one more social activity was associated with a reduction of depressive symptoms than in no social activities (odds ratio [OR] 0·90, 95% CI 0·87–0·93). Compared with the duration of 7–10 h of sleep at night, sleeping for less than 7 h was associated with a higher risk of depressive symptoms (OR 1·91, 95% CI 1·80–2·02). Additionally, current smokers were associated with increased risk of having depressive symptoms compared with never smokers (OR 1·21, 95% CI 1·09–1·33). Nevertheless, no significant association was observed between the presence of depressive symptoms and the individual status of being a past smoker, current drinker, and past drinker. InterpretationThe change in prevalence of depressive symptoms emphasises the need on establishing depression prevention programmes in China. Our results highlighted that smoking behaviour and a sleep duration less than 7 h might increase the risk of depressive symptoms among Chinese adults aged 45 years or more. Our study suggests that depression prevention programmes are likely to be benefitted by incorporating a series of social activities. FundingNone.