Impact of PM2.5 exposure in old age and its interactive effect with smoking on incidence of diabetes.

Purpose: To determine the impact of PM_2.5 exposure in old age and its interactive effect with smoking on incident diabetes.

Methods: A total of 2766 participants aged ≥60 years in China were interviewed at baseline for disease risk factors in 2001-03 and were then followed up for 10 years to document incident diabetes. They were assessed for daily PM_2.5 exposure in 2005. Multivariate Cox regression models were used to examine the association of PM_2.5 exposure with incident diabetes and interactive effect between PM_2.5 and smoking on incident diabetes.

Results: During the cohort follow-up, 176 participants developed diabetes. The incidence of diabetes increased with PM_2.5 exposure; the multiple-adjusted hazard ratio (HR) of diabetes was 2.27 (95 % CI 1.36-3.77) in participants with PM_2.5 at ≥62.0 μg/m³ compared to those at <62.0 μg/m³. There was a significant interaction effect of PM_2.5 with smoking on increased risk of diabetes. The adjusted HR for participants exposed to PM_2.5 levels ≥62.0 μg/m³ who smoked was 4.39 (95 % CI 1.72-11.21), while for non-smokers it was 1.65 (95 % CI 0.88-3.09), compared to those at <62.0 μg/m³.

Conclusions: Exposure to PM_2.5 in old age was associated with an increased incidence of diabetes and smoking enhanced the impact of PM_2.5 on diabetic risk. These findings underscore the urgent need for air quality improvement measures and smoking cessation programs to mitigate the risk of diabetes in aging populations.