Association between air pollution and type II diabetes in Italy from clinical data and population-weighted exposure at the municipality level

A growing body of literature supports the association between ambient particulate pollution and the risk of type 2 diabetes (T2DM). Both issues are particularly relevant in Italy. This study investigates the relationship between T2DM and exposure to PM_2.5 and PM₁₀ in Italian municipalities from 2013 to 2021. Data on T2DM were provided by the Italian Association of Diabetologists (AMD), representing the only national outpatient dataset not based on self-reported information. Air pollution data, sourced from the Italian Institute for Environmental Protection and Research, ISPRA, were summarized using the population-weighted exposure (PWE) indicator. Both datasets were made available through a dedicated research agreement. Random effects models and non-parametric methods were applied to assess the association between air pollution and T2DM. Results indicate a statistically significant relationship, particularly between T2DM and PM2.5. T2DM incidence rates were significantly negatively associated with time (coefficient = - 0.07961, p < 0.01), indicating a decreasing trend over time. After adjusting for other covariates, PM₁₀ population-weighted exposure was not significantly associated with incidence rates (coefficient = - 0.00057, p = 0.58). On the other hand, increases in the ratio of PM_2.5 to PM₁₀ (pwratio) were significantly positively associated with increases in T2DM incidence rates (coefficient = 0.52304, p < 0.01) at the municipal level. T2DM prevalence proportions were significantly positively associated with time (coefficient = 0.01749, p < 0.01), suggesting an increasing trend over time. PM₁₀ was significantly negatively associated with prevalence proportions (coefficient = - 0.00298, p = 0.03), while increases in pwratio were significantly positively associated with increases in prevalence proportions (coefficient = 0.18724, p < 0.01). Thus, municipalities with a higher share of PM_2.5 within the same level of PM₁₀, tended to show higher T2DM prevalence proportions and incidence rates, consistent with the spatial distribution of air pollution and disease burden observed across Italy.