Combined effects of social health and long-term exposure to fine particulate matter on cardiovascular disease in Chinese middle-aged and older adults

PurposeSocial isolation, loneliness, and fine particulate matter (PM2.5) exposure are significant social and environmental factors that frequently cooccur in vulnerable populations. The joint effects of these factors on the risk of cardiovascular disease (CVD), however, are not well supported by data. This study aimed to evaluate the independent and combined effects of social isolation, loneliness, and long-term PM2.5 exposure on CVD risk and to assess the interactions between social isolation or loneliness and PM2.5 exposure on CVD risk.MethodsWe used Cox proportional hazards models to estimate the independent and combined effects of loneliness, social isolation, and long-term PM2.5 exposure on CVD incidence. We also conducted interaction analyses to investigate whether the effects of social factors on CVD are modified by the level of PM2.5 exposure.ResultsThis study included 12,544 participants, with mean age of 58.7 +/- 9.4 years. The median follow-up was 7 years, with 1761 CVD events occurred. Individuals with loneliness presented a 29% increased risk of CVD (hazard ratio [HR] = 1.290, 95% confidence intervals [CI]: 1.165-1.428). A 10 mu g/m3 increase in PM2.5 exposure was associated with a 6% increase in CVD risk (HR = 1.060, 95% CI: 1.028-1.092). A significant additive interaction effect was observed between loneliness and PM2.5 on CVD (P for additive interaction = 0.042).ConclusionAmong Chinese middle and older adults, loneliness and long-term PM2.5 exposure had combined effects on CVD risk. The public health consequences of high PM2.5 exposure are more pronounced among individuals who experience feelings of loneliness.