Association between long-term fine particulate matter exposure and incident type 2 diabetes in a low-exposure Danish...

The global burden of type 2 diabetes (T2D) continues to rise, with evidence suggesting that air pollution may contribute to its pathogenesis. This study examines the association between long-term exposure to fine particulate matter (PM_2.5) and the risk of developing T2D in a cohort of older Danish men living in a low-exposure setting.

We conducted a prospective cohort study using 16,665 participants from the Viborg Vascular (VIVA) screening trial, aged 65-74 years without T2D at baseline. Residential PM_2.5 was modeled with the DEHM/UBM/AIRGIS system from historical address data; road-traffic noise was estimated with Nord2000. Cox models with age as timescale evaluated time-varying PM_2.5 exposure and T2D risk, adjusting for age, BMI, smoking status, socioeconomic factors, and traffic noise exposure.

Over a mean 9.3-year follow-up, 324 participants (1.9 %) developed T2D. Incidence was lower than reported in prevention trials, reflecting differences in population risk and registry-based outcome capture. Participants who developed T2D had slightly higher long-term PM_2.5 exposure compared to non-cases (12.12 vs 11.93 μg/m³; p < 0.001). Although absolute differences in exposure were small, they were consistent across the exposure distribution, suggesting a population-level effect even in a low-pollution environment. In adjusted time-varying Cox models, a 1.15 μg/m³ increment in PM_2.5 was associated with a 30.6 % higher risk of T2D (HR 1.306, 95 % CI 1.08-1.58; p = 0.006). Associations were independent of body mass index, smoking, socioeconomic status, and traffic noise.

Long-term PM_2.5 exposure was associated with T2D incidence in this cohort of older Danish men. Findings are hypothesis-generating, most applicable to low-to-moderate exposure settings, and should be interpreted with caution.