Long-term exposure to particulate air pollution associated with the progression of type 2 diabetes mellitus in China: effect size and urban–rural disparities

Abstract

Background: Recent Western studies link long-term particulate matter (PM) exposure to type 2 diabetes mellitus (T2DM) progression, but little is known for low- and middle–income countries. This study aimed to estimate the relationship between PM exposure and T2DM progression in China, and also assess urban–rural disparities. Methods: Using 7–year cohort data of 1.3 million Chinese over 40, a multistate model estimated the associations of PM exposure with T2DM progression. Covariates included demographics, socioeconomic status, health behaviors, medication, and meteorological factors. Sub–sample analyses were done for rural and urban areas. Results: For participants exposed to high levels of PM2.5, the 5–year absolute risks of developing T2DM and its complications were 4.31% (95% CI: 4.22–4.40) and 31.04% (95% CI: 29.97–32.08), respectively. In the low–PM2.5–exposure group, these risks were 3.82% (95% CI: 3.74–3.91) and 30.55% (95% CI: 29.43–31.65). For each 10 µg/m3 increase in PM2.5 exposure, the HRs (95% CI) for the progression from no T2DM diagnosis to a T2DM diagnosis were 1.13 (1.13–1.14), and for the progression from T2DM to the development of T2DM complications were 1.04 (1.03–1.06). Moreover, the HRs (95% CI) for mortality risk were 1.09 (1.08–1.09) for participants without T2DM, 1.06 (1.00–1.14) for those with T2DM, and 1.10 (1.05–1.16) for those with T2DM complications. Similar associations were observed for other PM–related metrics. In rural areas, PM exposure was more strongly associated with the progression from T2DM and its complications to death. Conversely, in urban areas, PM exposure had a stronger association with the progression from a non–T2DM state to a formal T2DM diagnosis. Urban residents are exposed to higher levels of toxic components like heavy metals, potentially increasing T2DM risk, yet urban healthcare infrastructure offers protection against T2DM–related mortality. Conclusions: PM exposure is significantly associated with T2DM progression. Urban areas should focus on primary prevention, while rural areas need to improve secondary and tertiary prevention like healthcare services.