Long-term low-level ozone exposure and the incidence of type 2 diabetes mellitus and glycemic levels: A prospective cohort study from Southwest China

Abstract

Background

This study investigated the relationship between long-term low-level ozone (O₃) exposure, type 2 diabetes mellitus (T2DM) incidence, and glycemic levels within a prospective cohort in Southwest China, especially in regions with relatively low air pollution levels.

Method

Between 2010 and 2020, the Guizhou Population Health Cohort Study (GPHCS) enrolled 9280 participants, who were followed up from 2016 to 2020. A total of 7317 participants (aged 18–95 years, mean 43.70 ± 14.89 years) were included in the final analysis. Time-dependent Cox regression models were used to evaluate the hazard ratios (HRs) between O₃ exposure and T2DM incidence and its 95 % confidence intervals (CIs). Generalized linear model (GLM) assessed the association between O₃ exposure and fasting blood glucose (FBG) levels.

Results

During a median follow-up period of 6.58 (6.25, 8.42) years, 763 participants were diagnosed with T2DM. For every 1 standard deviation (SD) increase in O₃ exposure (Mean ± SD: 67.23 ± 2.16 μg/m³) during the 6 years before baseline, the incidence of T2DM increased by 32.4 % (HR = 1.324, 95 % CI: 1.216, 1.442), while FBG levels rose by 0.081 mmol/L (β = 0.081, 95 % CI: 0.035,0.126). These associations persisted after adjusting for potential confounders, including PM_2.5 and temperature. Stratified analyses revealed stronger associations in Han Chinese and urban populations.

Conclusion

This study provides robust evidence that even long-term exposure to low-level O₃, below the World Health Organization (WHO) guideline value, is significantly associated with increased T2DM incidence and elevated FBG levels. These findings stress the need for stricter air pollution control measures to reduce the incident T2DM caused by long-term low-level O₃ exposure and enhance public health protections.