Long-term air pollution exposure and diabetes risk in the elderly population.

Objective: Type 2 diabetes mellitus is a major public health concern. We assessed the association between air pollution and first documented diabetes occurrence in a national U.S. cohort of Medicare enrollees to estimate incidence risk. Research design and methods: We included all Medicare enrollees 65 years and older in the fee-for-service program, part A and part B, in the contiguous United States (2000-2016). Participants were followed annually until the first recorded diabetes diagnosis, end of enrollment, or death. We obtained air pollution annual estimates of fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) exposures from highly spatiotemporally resolved prediction models. We assessed the simultaneous effect of the pollutants on diabetes incidence using Poisson survival analysis with adjustment for temporal and spatial confounders. We repeated the models in data restricted to ZIP codes with air pollution levels not exceeding the ambient air quality standards during the study period. Results: We have included 264,869,458 person-years of 41,780,637 people. We observed nonlinear associations between the three pollutants and diabetes, with larger risks at lower levels for PM2.5 and O3. When restricting the data to lower air pollution levels, an increased risk for diabetes (Incidence Rate Ratio [95% Confidence Interval] was associated with interquartile range (IQR) increases in PM2.5 (1.048 [1.045;1.051]), O3 (1.016 [1.014;1.18]), and NO2 (1.040 [1.037; 1.043]). Conclusion: We found increased diabetes risk associated with air pollution exposures. The observed effects remained in exposure levels below the national ambient air quality standards in the U.S.