Long-term exposure to ambient air pollution and risk of microvascular complications among patients with type 2 diabetes: a prospective study.

Background Patients with type 2 diabetes (T2D) may disproportionately suffer the adverse cardiovascular effects of air pollution, but relevant evidence on microvascular outcome is lacking. We aimed to examine the association between air pollution exposure and the risk of microvascular complications among patients with T2D. Methods This prospective study included 17 995 participants with T2D who were free of macro- and micro-vascular complications at baseline from the UK Biobank. Annual average concentrations of particulate matter (PM) with diameters <2.5 μm (PM_2.5), <10 μm (PM₁₀), nitrogen dioxide (NO₂) and nitrogen oxides (NO_x) were assessed using land use regression models. Cox proportional hazards regression was used to estimate the associations of air pollution exposure with incident diabetic microvascular complications. The joint effects of the air pollutant mixture were examined using quantile-based g-computation in a survival setting. Results In single-pollutant models, the adjusted hazard ratios (95% confidence intervals) for composite diabetic microvascular complications per interquartile range increase in PM_2.5, PM₁₀, NO₂ and NO_x were 1.09 (1.04–1.14), 1.06 (1.01–1.11), 1.07 (1.02–1.12) and 1.04 (1.00–1.08), respectively. Similar significant results were found for diabetic nephropathy and diabetic neuropathy, but not for diabetic retinopathy. The associations of certain air pollutants with composite microvascular complications and diabetic nephropathy were present even at concentrations below the World Health Organization limit values. Multi-pollutant analyses demonstrated that PM_2.5 contributed most to the elevated risk associated with the air pollutant mixture. In addition, we found no interactions between air pollution and metabolic risk factor control on the risk of diabetic microvascular complications. Conclusions Long-term individual and joint exposure to PM_2.5, PM₁₀, NO₂ and NO_x, even at low levels, was associated with an increased risk of diabetic microvascular complications, with PM_2.5 potentially being the main contributor. [ABSTRACT FROM AUTHOR]