Impact of PM 2.5 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 mu g/m(3) compared to those at <62.0 mu g/m(3). 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 mu g/m(3) 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 mu g/m(3). 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.