Air pollution and Type 2 Diabetes in Europe: Insights from nonlinear exposure-response modelling

Air pollution is currently one of the major environmental problems related to human health, affecting many diseases. In this regard, while studies have established an association between air quality and Type 2 Diabetes Mellitus (T2DM), there is still a need to refine exposure-response functions. Therefore, this study aims to establish the exposure-response function that relates the concentration of two air pollutants (NO₂ and PM_2.5) to the hazard ratio associated with acquiring T2DM, based on various cohort studies conducted worldwide. To achieve this, a methodology using nonlinear function adjustments will be employed. This function is then applied to determine the number of T2DM cases attributable to air pollution across Europe for different age groups, using atmospheric concentrations from 1991 to 2020. Results indicate a significant nonlinear relationship between pollutant exposure and T2DM cases, with higher risks observed in areas with elevated levels of NO₂ and PM_2.5 (specifically, in large European cities and in central Europe, mainly related to traffic and industrial activities). NO₂ relates to 3754000 [3428000 - 3957000; 95% CI] annual T2DM cases, which represent 0.51% [0.46%-0.54%; 95% CI]; while PM_2.5, annual cases increase to 5109000 [4036000 - 6581000; 95% CI], corresponding to a 0.69% [0.55%-0.89%; 95% CI] of cases of T2DM attributable to this pollutant. The analysis revealed that, despite lower concentrations, PM_2.5 shows a higher impact on T2DM incidence compared to NO₂, especially at lower exposure levels. Findings underscore the need for stringent air quality regulations, particularly in urban and industrial regions, to mitigate air pollution's health impacts.