Traffic-related NOx exposure and proximity to freeways are related to adverse changes in subclinical atherosclerosis measures from childhood to adulthood

Background: Chronic exposure to air pollutants is associated with increased risk of cardiovascular disease (CVD) among adults. However, little is known about how air pollution may affect the development of subclinical atherosclerosis in younger populations. Subclinical measures of atherosclerosis, including carotid artery intima-media thickness (CIMT) and arterial stiffness (CAS), may provide insight into early CVD pathogenesis. Methods: In a pilot study of 70 participants from the Southern California Children’s Health Study, we investigated subclinical atherosclerosis progression from childhood to adulthood. Using carotid artery ultrasound images obtained at age 10 and follow-up images from age 21-22, we examined associations between traffic-related pollutants and changes in CIMT and CAS. Lifetime average traffic-related NOx exposures were assigned using the CALINE4 (California Line Source) dispersion model. Distance to nearest roadways by class was assigned based on ESRI Streetmap Premium roadway data. Results: For each interquartile range increase in average lifetime NOx exposure, we observed a 12.12μm (95% CI: 1.11-23.13; p=0.03) increase in early adulthood attained CIMT and greater longitudinal changes in CIMT from childhood to adulthood (11.5μm, 95% CI: 1.29-21.73, p=0.03) over the follow-up period. Similar adverse changes in CIMT were observed with distance to nearest freeway. Changes in CAS were related to distance to freeway, such that living in closer proximity to freeways was related to greater adverse change in CAS over the follow-up period (stiffness index beta: 0.85; 95% CI: 1.50, 0.21, p=0.01; distensibility: -5.61; 95% CI: -0.93, -10.27, p=0.02).Conclusions: We observed greater adverse changes measures of carotid artery wall thickness and stiffness over time in relation to lifetime traffic-related NOx exposure and residential proximity to freeways. To our knowledge, this is the first study to evaluate the longitudinal impact of lifetime traffic-related air pollution exposure on changes in subclinical markers of atherosclerosis during the critical transition from childhood to adulthood.