Synergistic effects of air pollution and artificial light at night on diabetes risk: A prospective cohort study

Previous studies have indicated associations between air pollutants, outdoor artificial light at night (ALAN) exposure, and diabetes risk, but their interactive effects remain insufficiently validated. Based on data from two large Chinese cohorts (CHARLS and CFPS) with 28,903 participants followed for 3 years (2013-2018), we employed Cox proportional hazards regression models to evaluate the associations of pollutants and outdoor ALAN with diabetes incidence risk and their interactions, along with stratified analyses. Results demonstrated significant linear relationships between PM₁ and PM_2.5 concentrations and diabetes risk. Each 10 microg/m³ increase in PM₁ and PM_2.5 was associated with hazard ratios (HRs) of 1.065 (95 % CI: 1.061-1.069) and 1.036 (95 % CI: 1.034-1.038), respectively. Other pollutants (SO₂, NO₂, and CO) and outdoor ALAN exposure showed non-linear associations with diabetes risk, with each standard deviation increase in outdoor ALAN exposure associated with an HR of 1.004 (95 % CI: 1.001-1.007). Furthermore, co-exposure to PM₁, PM_2.5, PM₁₀, and SO₂ with outdoor ALAN demonstrated significant additive effects. Stratified analyses revealed significantly higher diabetes risks among individuals aged ≥65 years and unmarried populations. Regional differences showed higher pollutant susceptibility among northern residents, while southern residents demonstrated greater sensitivity to outdoor ALAN exposure. This study revealed for the first time significant synergistic effects between environmental pollutants and outdoor ALAN exposure on diabetes risk, highlighting the importance of environmental and light pollution in diabetes prevention and control, and providing theoretical basis for future policy development.