No adverse effect of outdoor air pollution on HbA1c in children and young adults with type 1 diabetes.

BACKGROUND:Evidence is growing that air pollutants deteriorate glucose metabolism and insulin sensitivity by oxidative stress and inflammation. This might affect HbA1c levels and insulin requirements in type 1 diabetes. There are no data available on this association. METHODS:Air pollution values of respirable particulate matter (PM10), nitrogen dioxides (NO2), and accumulated ozone (O3-AOT40) were obtained from the federal environmental agency (Umweltbundesamt II) and assigned to place of residence of 840 participants from a nation-wide population-based type 1 diabetes registry (German Diabetes Center, Düsseldorf, Germany). Information on HbA1c, social status, treatment and co-morbidities was collected by self-administered questionnaires. Complete information was available for 771 patients aged 11-21 years at the time of study. RESULTS:In linear regression models, no adverse effects of air pollutants (PM10, NO2 or O3-AOT40 on HbA1c level were found, but O3-AOT40 was inversely associated with HbA1c (mmol/mol) in the crude (estimate per IQR: -1.86; 95% CI: (-3.27; -0.44); p=0.01) and the best model adjusting for lifestyle, socioeconomic factors, clinical information, and season (-1.50; (-2.82; -0.17); 0.034). After adding area of residency as random effect to the crude and the best model, the association was no longer significant (-1.64; (-3.84; 0.56); 0.14); (-1.56; (-3.67; 0.55); 0.14). Adjustment for further possible confounders did not affect the estimates seriously. None of the pollutants was associated with insulin dose (IU/kg body weight). CONCLUSIONS:Investigated pollutants had no adverse effect on metabolic control in children and young adults with type 1 diabetes in this cross-sectional study. The weak inverse association of accumulated ozone with HbA1c might be due to confounding by regional characteristics or regional aspects of care.