Exposure to Ambient Air Pollution and Correlates of Cardiovascular Disease among Youth with Type 1 Diabetes

Abstract

Air pollution from traffic-related sources is associated with cardiovascular disease (CVD), potentially through changes in systemic inflammatory responses, vascular function and oxidative stress leading to atherosclerosis, thrombosis or endothelial dysfunction. Individuals with type 1 diabetes (T1D) have a greater risk of CVD-related morbidity and mortality than the general population, and they may be more susceptible to the effects of air pollution on CVD. Although these increased risks begin during childhood, very few studies have assessed the impact of air pollution on children and youth with T1D. This dissertation directly addresses gaps in the epidemiologic evidence by: 1) evaluating the relationship of short-term exposures to traffic-related air pollutants with pulse wave velocity (PWV), a measure of arterial stiffness, 2) assessing the effects of changes in air pollution exposures on changes in inflammatory biomarkers, including C-reactive protein, fibrinogen and interleukin-6 (IL-6), and 3) examining the relationship of long-term exposures to traffic-related air pollution with allostatic load (AL), a measure of cumulative biological risk, among a cohort of youth with T1D.

Data were obtained from the SEARCH for Diabetes in Youth (SEARCH) study. SEARCH was initiated in 2000 and includes a diverse population of US youth diagnosed with diabetes prior to age 20 years. Anthropometric and laboratory measures were taken at SEARCH study visits, and standardized questionnaires were used to collect information on important covariates. Air pollution exposures were estimated using spatio-temporal models and assigned to residential addresses for each participant.

In the first study, we identified a significant association between increased exposure to PM2.5 on the day of the examination with higher PWV using generalized linear models adjusted for lifestyle and demographic characteristics. In the second analysis, we found consistent positive effects of increases in PM2.5 over the week prior to the examination with IL-6 using longitudinal mixed models. In the third study, no significant associations were observed for monthly and annual PM2.5 exposures or proximity to major roadways with AL in fully adjusted linear mixed models. However, effects differed by race/ethnicity and gender. Overall, this research indicates that youth with T1D may be at higher risk for air pollution-related cardiovascular impacts.