Inflammation and acute traffic-related air pollution exposures among a cohort of youth with type 1 diabetes

Abstract

Background: Evidence remains equivocal regarding the association of inflammation, a precursor to cardiovascular disease, and acute exposures to ambient air pollution from traffic-related particulate matter. Though youth with type 1 diabetes are at higher risk for cardiovascular disease, the relationship of inflammation and ambient air pollution exposures in this population has received little attention.

Objectives: Using five geographically diverse US sites from the racially- and ethnically-diverse SEARCH for Diabetes in Youth Cohort, we examined the relationship of acute exposures to PM_2.5 mass, Atmospheric Dispersion Modeling System (ADMS)-Roads traffic-related PM concentrations near roadways, and elemental carbon (EC) with biomarkers of inflammation including interleukin-6 (IL-6), c-reactive protein (hs-CRP) and fibrinogen.

Methods: Baseline questionnaires and blood were obtained at a study visit. Using a spatio-temporal modeling approach, pollutant exposures for 7 days prior to blood draw were assigned to residential addresses. Linear mixed models for each outcome and exposure were adjusted for demographic and lifestyle factors identified a priori.

Results: Among the 2566 participants with complete data, fully-adjusted models showed positive associations of EC average week exposures with IL-6 and hs-CRP, and PM_2.5 mass exposures on lag day 3 with IL-6 levels. Comparing the 25th and 75th percentiles of average week EC exposures resulted in 8.3% higher IL-6 (95%CI: 2.7%,14.3%) and 9.8% higher hs-CRP (95%CI: 2.4%,17.7%). We observed some evidence of effect modification for the relationships of PM_2.5 mass exposures with hs-CRP by gender and with IL-6 by race/ethnicity.

Conclusions: Indicators of inflammation were associated with estimated traffic-related air pollutant exposures in this study population of youth with type 1 diabetes. Thus youth with type 1 diabetes may be at increased risk of air pollution-related inflammation. These findings and the racial/ethnic and gender differences observed deserve further exploration.

Keywords: Diabetes; Inflammation; Traffic-related air pollution.

Fig. 1.

Percent difference in IL-6 levels with an IQR change in estimated EC, PM_2.5 and ADMS roads exposures in fully-adjusted models. *Model adjusts for site, age, gender, residential census tract percent below poverty, physical activity, sedentary behavior and smoking.

Fig. 2.

Percent difference in hs-CRP levels with an IQR change in estimated EC, PM₂.₅ and ADMS roads exposures in fully-adjusted models. *Model adjusts for site, age, gender, residential census tract percent below poverty, physical activity, sedentary behavior and smoking.

Fig. 3.

Percent difference in fibrinogen levels with an IQR change in estimated EC, PM_2.5 and ADMS roads exposures in fully-adjusted models *Model adjusts for site, age, gender, residential census tract percent below poverty, physical activity, sedentary behavior and smoking.