Quantile regression to examine the association of air pollution with subclinical atherosclerosis in an adolescent population

Abstract

BACKGROUND AND AIM: Air pollution has been associated with early risk factors for later cardiovascular outcomes, including carotid intima-media thickness test (CIMT), a marker of subclinical atherosclerosis. To our knowledge, this is the first study to examine the association between air pollution exposure and CIMT in a younger adolescent population. We utilize quantile regression to examine the associations beyond mean regression analysis and examine if associations occur in the tails of the CIMT distribution. METHODS: We measured CIMT at the age of 16 years in 418 adolescents participating in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) population-based birth cohort in the Netherlands. We fit separate quantile regressions to examine whether the associations of annual averages of air pollutants up to age 14 for nitrogen dioxide (NO2), fine particulate matter (PM2.5), PM2.5 absorbance (a marker for black carbon) and PM coarse assigned at the participants’ residential addresses varied across deciles of CIMT. We report the quantile regression coefficients that corresponded to an average change in CIMT (µm) associated with an interquartile range increase in the air pollution concentrations. Models were adjusted for age, sex, body mass index (BMI), gestational age at birth and birthweight, parental education, parental smoking status and maternal BMI and breastfeeding status. RESULTS:Interquartile range increases in NO2, PM2.5 and PM2.5 absorbance during the first 2 years of life were associated with significantly higher CIMT in the lower tails of the distribution. NO2 exposure at birth had the largest statistically significant association with a 7.22 µm (95% CI: 5.28, 10.42) increase per IQR increase in NO2 for the 10th quantile of CIMT but was not significantly related to the 50th quantile (estimate: 1.64 µm, 95% CI: -1.49, 6.78). CONCLUSIONS:Early childhood exposure to air pollution concentrations was associated with an increase at the lower tails of the CIMT distribution during adolescence. KEYWORDS: Quantile regression, Environmental Epidemiology, Air pollution, Cardiovascular, Atherosclerosis