Long-term exposure to ambient air pollution, circadian syndrome and cardiovascular disease: A nationwide study in China

Epidemiological evidence suggests associations between ambient air pollution and cardiovascular disease (CVD), while circadian rhythm dysregulation, presented by circadian syndrome (CircS), is emerging as a new proxy to cardiovascular disorder that could provide a bridge between them. The present study aims to clarify the effect of high levels ambient air pollution exposure on CircS and CVD in China.From the China Health and Retirement Longitudinal Study, we recruited 9116 Chinese participants in 2011 and followed them to 2015. A spatiotemporal model was applied to estimate exposure to particles with diameters ≤2.5 μm (PM2.5). The variable CircS was defined based on 7 components, including the 5 components used to define metabolic syndrome as well as other two components, lack of sleep and depression. The associations between PM2.5 exposure and prevalent CircS as well as incident CVD were modeled via logistic regression analysis displaying odds ratios (ORs) and 95 % CIs (confidence intervals). A mediation analysis was undertaken to identify the potential mediating role of CircS between PM2.5 exposure and CVD.The mean age (standard deviation) was 59 (9) and 48.22 % were male. The OR (95 % CI) between the highest (Q4) and the lowest (Q1) quartile of PM2.5 exposure for CircS was 1.13 (1.01-1.28) in 2011 and 1.44 (1.22-1.72) in 2015. The cumulative effect of the components of CircS became more obvious with the increase of the PM2.5 quartile exposure. For the Q4 versus Q1 of PM2.5 increment, the multivariate-adjusted OR (95 % CI) was 1.66 (1.20-2.29) for CVD incidence. CircS partially mediated the association between PM2.5 exposure and CVD.Exposure to PM2.5 is a risk factor for CircS and CVD, and the effect of PM2.5 on CVD may be explained by CircS. Improving air quality would have high value in preventing CircS as well as CVD in public health.