Associations between long-term exposure to air pollution, glycosylated hemoglobin, fasting blood glucose and diabetes mellitus in northern France

Introduction: A growing body of evidence suggests that long-term exposure to air pollutants like nitrogen oxides (NOx) and particulate matter (PM) is associated with the prevalence and incidence of type 2 diabetes mellitus. Serum glucose and glycosylated hemoglobin (HbA1c) levels are biomarkers of glucose homeostasis. Data on the association between glucose homeostasis biomarkers and air pollution are scarce. HbA1c and fasting blood glucose (FBG) concentrations have been linked to PM and NO2 exposure in Taiwan, where mean pollution levels are 3 to 7 times higher than the guideline maximum annual mean values of 40 mu g/m(3) (for NO2) and 20 mu g/m(3) (for PM10) set by the World Health Organization (WHO). However, this association is not consistently reported at lower levels of pollution. The objective of the present study was to investigate the relationships between long-term exposure to air pollution at the place of residence, diabetes biomarkers, and prevalent diabetes in two cities with relatively low level of pollution. Methods: Data were recorded for 2895 adults (aged 40 to 65) having participated in the 2011-2013 ELISABET cross-sectional survey of the Lille and Dunkirk urban areas in northern France. Using multiple logistic and generalized linear regression models, we analyzed the associations between individual exposure to pollution on one hand and HbA1c, FBG and prevalent diabetes mellitus (DM) on the other. An atmospheric dispersion modelling system was used to assess annual exposure at the place of residence to coarse particulate matter (PM10), NO2, and sulfur dioxide (SO2). Results: The median pollutant levels were 21.96 mu g/m(3) for NO2, 26.75 mu g/m(3) for PM10, and 3.07 mu g/m(3) for SO2. A 2 mu g/m(3) increment in PM10 was associated with an HbA1c increment [95% confidence interval] of 0.044% [0.021; 0.067]. This association was still statistically significant after adjustment for the neighborhood's characteristics. A 5 mu g/m(3) increment in NO2 was associated with an HbA1c increment of 0.031% [0.010; 0.053]. Associations between DM or FBG and air pollution did not achieve statistical significance. Conclusion: Our study of a middle-aged, urban population evidenced an association between elevated HbA1c levels and long-term exposure to PM10 and NO2 pollution levels that were relatively low but close to the WHO's guideline maximum values.