Air pollution, drought, and their synergistic effects on cardiovascular disease risk in China: a nationwide study

Air pollution and drought are both critical environmental challenges that adversely affect human health. Nevertheless, their combined impact on the risk of cardiovascular disease (CVD) has not been investigated. This study utilized data from the China Health and Retirement Longitudinal Study (CHARLS), comprising 12,792 participants in a cross-sectional analysis and 9265 participants in a longitudinal analysis (2011-2018). We examined the associations between long-term exposure to nitrogen dioxide (NO₂), ozone (O₃), and a composite measure of oxidative potential (O_X), with the occurrence of cardiovascular conditions such as heart disease and stroke. Air pollution metrics (NO₂ and O₃) were derived from the ChinaHighAirPollutants dataset, and O_X was estimated accordingly. Drought intensity was evaluated using the Standardized Drought Index (SDI). Our findings revealed that elevated levels of NO₂, O₃, and Ox were significantly associated with increased risks of heart disease and stroke. Specifically, each interquartile range (IQR) rise in O_X was associated with increased odds of heart disease, with an odds ratio (OR) of 1.42 (95% CI: 1.35-1.50) and higher odds of stroke (OR = 1.52; 95% CI: 1.39-1.66). O₃ exposure showed comparable results, with odds ratios of 1.49 (95% CI: 1.42-1.55) for heart disease and 1.55 (95% CI: 1.36-1.74) for stroke. Exposure to NO₂ was also significantly linked with higher odds of heart disease (OR = 1.35; 95% CI: 1.28-1.42) and stroke (OR = 1.40; 95% CI: 1.26-1.55). Furthermore, the adverse effects of air pollutants on cardiovascular outcomes were more pronounced in areas experiencing severe drought (OR = 1.32, 95% CI: 1.21-1.44 for CVD). The joint exposure analysis further demonstrated that individuals subjected to both high air pollution and severe drought faced the greatest risk of cardiovascular issues (OR = 2.15, 95% CI: 2.00-2.30 for CVD), surpassing those in lower exposure groups. These results emphasize the amplified health risks arising from the interaction of environmental pollutants and climate stressors, pointing to the necessity for comprehensive public health approaches that simultaneously target air quality and climate resilience.