Effects of long-term exposure to CO and PM_2.5 on microalbuminuria in type 2 diabetes

Objective: No study has examined the effects of air pollutants on albuminuria in type 2 diabetes. Therefore, the present study investigated this association. Methods: This follow-up study enrolled 812 patients with type 2 diabetes between 2003 and 2012. The urinary albumin-to-creatinine ratio (ACR) was recorded annually. Exposure to the air pollutants CO, NO₂, O₃, SO₂, and PM_2.5 was interpolated from 72 air-quality monitoring stations to residences by using the kriging method. The association between air pollutants and ACR increase was assessed using mixed-effect model with random intercepts for 36 clinics. Results: The study objects (mean age: 55.4 years) were followed for 3 or more years (average period: 5.4 years). ACR increase was found to be positively associated with the male sex, baseline hemoglobin A1c, and exposure to CO and PM_2.5, and negatively associated with waist circumference through multiple linear regression. Annually urine albumin/creatinine ratio increase was estimated by the final model, Patients exposed to higher levels of CO (e.g., third quartile, 1025 ppb) and lower levels of CO (e.g., first quartile, 850 ppb) had an annual ACR increase of 3.73 and 3.54 mg/g, respectively. Patients exposed to higher levels of PM_2.5 (e.g., third quartile, 38.8 μg/M3) and lower levels of PM_2.5 (e.g., first quartile, 27.7 μg/M3) had an annual ACR increase of 3.96 and 3.17 mg/g, respectively. Conclusions: Exposure to high CO and PM_2.5 levels increased albuminuria in type 2 diabetes.