Design: Cross-sectional surveys performed between 1985-1994 in the highly industrialized Ruhr district (West-Germany) with a follow-up investigation in 2006 (SALIA: Study on the influence of Air pollution on Lung, Inflammation and Aging cohort).
Participants: 1775 women (non-diabetic and aged 54-55 years at baseline) participated in both baseline and follow-up investigations and had complete information available.
Evaluations/Measurements: 16-year incidence (1990-2006) of type 2 diabetes as well as information about covariates were assessed by questionnaires. Complement factor C3c as marker for subclinical inflammation was measured at baseline. Individual exposure to traffic-related particulate matter (PM) and nitrogen dioxide was determined at different spatial scales.
Results: 187 (10.5%) new cases of diabetes were reported (1990-2006). The hazards for diabetes were increased by 15-42% per inter-quartile range of PM or traffic-related exposure. The associations persisted when different spatial scales were used to assess exposure and remained robust after adjustment for age, body mass index, socioeconomic status and exposure to several non-traffic-related sources of air pollution. C3c was associated with PM pollution at baseline and was a strong independent predictor of incident diabetes. Exploratory analyses indicated that women with high C3c blood levels were more susceptible for PM-related excess risk of diabetes than women with low C3c levels.
Conclusions: Traffic-related air pollution is associated with incident type 2 diabetes in elderly women. Subclinical inflammation may be a mechanism linking air pollution with type 2 diabetes.