Ethnic disparities in the association between ambient air pollution and risk for cardiometabolic abnormalities in China

Background: Long-term exposure to ambient air pollution has been associated with cardiometabolic abnormalities (CAs), which, however, may be stronger in vulnerable populations, such as minorities. The variation of the association between ambient air pollution and CAs between the majority (Han) and minority populations in China have been poorly studied. Objectives: We aimed to estimate and compare the Hans' and minorities' risks for CAs associated with long-term exposure to ambient air pollution in Southwest China. Methods: A cross-sectional study was conducted on the basis of the China Multi-Ethnic Cohort. CAs were defined by the presence of at least three pre-defined metabolic dysfunctions (central obesity, elevated triglycerides, reduced high-density lipoprotein cholesterol, elevated blood pressure, and elevated fasting glucose). The concentrations of ambient air pollutants, including particulate matters (PM₁, PM_2.5, and PM₁₀) and nitrogen dioxide (NO₂), were generated from random forest models on the basis of multi-source data. One- and two-pollutant regression models were fit to assess associations between air pollutant exposure and CA risks. Sensitivity analyses were performed to examine the robustness of the associations. Results: The final sample included 51,037 Hans and 28,702 minority participants. The prevalence of CAs was 25.0%, slightly higher in the minorities (25.5%) than the Hans (24.4%). The higher risks for CAs in the overall population were associated with each 10 μg/m³ increase in the exposure to PM₁ (OR = 1.07 [1.05–1.09]), PM_2.5 (OR = 1.11 [1.06–1.17]), PM₁₀ (OR = 1.04 [1.03–1.06]), and NO₂ (OR = 1.04 [1.03–1.07]). Compared to the Hans, the higher risks for CAs were observed in the minorities for PM₁ (OR = 1.35 [1.18–1.53]), PM_2.5 (OR = 1.61 [1.34–1.93]), and PM₁₀ (OR = 1.15 [1.07–1.23]). The associations of metabolic dysfunctions (CA components) with ambient air pollution also varied between the Han and minority populations. Conclusions: The associations between exposure to ambient air pollution and CA risks were stronger in the minorities than Hans. Our findings provide a better understanding of ethnic disparities in CA risks when being exposed to ambient air pollution in China, which also have important implications for other low- and middle-income countries where less health resources (e.g., cohort populations) are available to conduct such studies.