Fine particulate matter and body weight status among older adults in China: Impacts and pathways

Background: Population ageing and air pollution have become two major public health concerns in China. Longitudinal evidence on the body weight impacts of air pollution among older adults is rare. This study aims to investigate the impacts of ambient particulate matter with aerodynamic diameters <2.5 mu m (PM2.5) on weight status of older adults in China and the potential behavioral and metabolic pathways through which PM2.5 influences weight status. Methods: The longitudinal data from the China Health and Retirement Longitudinal Study (body mass index-BMI, n = 9053; waist/height ratio-WHR, n = 9064) were linked to the air pollution data at the city-level with a rural-urban distinction. We used mixed-effects linear models to evaluate the impacts of PM2.5 on individual weight status and multiple mediation analysis to examine potential pathways. Results: After adjusting for relevant socioeconomic and city-level risk factors, significant and robust positive impacts of PM2.5 on BMI (0.025, 95%CI: 0.018, 0.031) and WHR*100 (0.058, 95%CI: 0.044, 0.072) were found among older adults in China. The PM2.5-weight status relationship among older adults may be mediated through metabolic and inflammatory dysfunction pathways particularly HbA1c and C-reactive protein (CRP). As PM2.5 deteriorates, the detrimental impacts tend to be more severe for rural-urban migrants and rural residents, compared to their urban counterparts. The worsening rural PM2.5 profiles in some areas, such as the northern parts of the Central and the Eastern, may leave them particularly vulnerable to air pollution. Conclusions: PM2.5 has an independent and significant detrimental impact on weight status including BMI and WHR of older adults in China, especially among rural adults and rural-urban migrants. PM2.5 may affect weight status of older adults through biomarkers such as HbA1c and CRP. More research is needed to confirm our findings.