Type 2 diabetes and the urban exposome: Role of air pollution, noise, and built environment in the risk of type 2 diabetes: systematic review and meta-analysis

Air pollution, noise, and built environment are associated with the epidemics of type 2 diabetes (T2D). The extent to which these have independent and/or joint effects on T2D and whether some components of the urban exposome have stronger effects remains unclear. We conducted a systematic review of the associations of 11 environmental exposures of urban exposome with the risk of T2D. We searched PubMed and Scopus since 2005 until January 2025 for studies on association of T2D in adults with air pollution; particles with a diameter of less than 2.5 (PM2.5) and 10 µm (PM10), nitrogen dioxide (NO2), ozone (O3) and black carbon (BC), noise; traffic-, railway-, and aircraft noise, and built environment; greenness, walkability, and population density. We included 151 articles, one study referring to exposome approach. Air pollutants were associated with T2D risk in meta-analyses, BC showing strongest association, OR: 1.32, 95% CI: 1.15-1.50 (n = 8). Subgroup analyses and meta-regression for PM2.5, PM10, NO2, and O3 by study characteristics highlighted variations in risk estimates but didn’t explain considerable heterogeneity. Traffic noise was associated with T2D (OR: 1.06, 95% CI: 1.03, 1.08, n = 11). In qualitative synthesis, living environment with higher walkability and greenness showed inverse association with T2D. Results indicate that air pollution and traffic noise are associated with increased risk of T2D. Greener and walkable living environment can potentially reduce risk of T2D. It remained unclear whether the effects were independent. Future studies should consider environmental joint exposures. Advancing use of exposome approach can help understand T2D risk comprehensively.