Associations of residential greenness and ambient air pollution with overweight and obesity in older adults.

Abstract

This study aimed to examine the impact of greenness and fine particulate matter <2.5 μm (PM_2.5 ) on overweight/obesity among older adults in China. A total of 21,355 participants aged ≥65 years were included from the Chinese Longitudinal Healthy Longevity Survey between 2000 and 2018. Normalized difference vegetation index (NDVI) with a radius of 250 m and PM_2.5 in a 1 × 1-km grid resolution were calculated around each participant's residence. Cox proportional hazards models were used to estimate the effects of NDVI and PM_2.5 on overweight/obesity. Interaction and mediation analyses were conducted to explore combined effects. The study observed 1895 incident cases of overweight/obesity over 109,566 person-years. For every 0.1-unit increase in NDVI the hazard ratio of overweight/obesity was 0.91 (95% CI: 0.88-0.95), and for every 10-μg/m³ increase in PM_2.5 the hazard ratio was 1.11 (95% CI: 1.07-1.14). The effect of NDVI on overweight/obesity was partially mediated by PM_2.5 , with a relative mediation proportion of 20.10% (95% CI: 1.63%-38.57%). Greenness exposure appears to lower the risk of overweight/obesity in older adults in China, whereas PM_2.5 , acting as a mediator, partly mediated this protective effect.