To assess the effect of long-term exposure to air pollution on type 2 diabetes risk, a meta-analysis of prospective cohort studies was performed.
Literature search was conducted with Pubmed, Embase, and Web of Science for prospective cohort studies investigating the association of type 2 diabetes risk with increments in particulate matter (PM, diameter <2.5 μm (PM2.5) or <10 μm (PM10)) or nitrogen dioxide (NO2). We used a random-effects model to calculate the overall relative risk (RR) with 95% CI.
Of 808 identified articles, ten cohort studies were finally included, which involved a total of 2 371 907 participants and 21 095 incident cases of type 2 diabetes. Elevated risk of type 2 diabetes was significantly associated with long-term exposures to high levels of PM2.5 (RR=1.28, 95% CI 1.06–1.55, P=0.009, I 2=83.5%), PM10 (RR=1.15, 95% CI 1.02–1.30, P=0.022, I 2=0%), and NO2 (RR=1.12, 95% CI 1.02–1.23, P=0.015, I 2=63.5%). When using standardized risk estimates, the RRs of type 2 diabetes were significant for increments in concentrations of PM2.5 (1.39 per 10 μg/m3 increment, 95% CI 1.14–1.68, P=0.001), PM10 (1.34 per 10 μg/m3 increment, 95% CI 1.22–1.47, P<0.001), and NO2 (1.11 per 10 μg/m3 increment, 95% CI 1.07–1.16, P<0.001). No obvious evidence of publication bias was observed.
Long-term exposure to high levels of main air pollutants is significantly associated with elevated risk of type 2 diabetes mellitus.