Traffic-related air pollution and childhood obesity in an Italian birth cohort

Background: Air pollution is associated with several adverse health outcomes in children, such as respiratory illnesses and cognitive development impairment. There are suggestions of an effect of traffic-related air pollution on the occurrence of childhood obesity, but the results are not consistent. Objectives: The aim of the study is to analyse whether air pollution and vehicular traffic exposure, during the first four years of life, influence obesity-related measures among 4 and 8-year-old children from a prospective birth cohort in Rome. Methods: A cohort of newborns, enrolled in 2003-2004 within the GASPII project, was followed at 4 and 8 years of age with parental interviews and clinical examinations. Air pollution was assessed at residential address using Land Use Regression models (for NO2, NOx, PM10, PM2.5, PMcoarse, PM2.5 absorbance and one traffic variable (Total traffic load of all roads in a 100 m buffer)). The outcomes under study were body mass index (BMI Z scores according to WHO recommendations, considered both categorical and continuous) measured at 4 and 8 years, and, waist circumference, waist-to-hip ratio, total and HDL cholesterol measured at 8 years. The associations were evaluated through both cross-sectional and longitudinal approaches, using logistic regression models, Generalized Estimating Equation models (GEE) and linear regression models, as appropriate. Moreover, Inverse Probability Weighting (IPW) methodology was used to account for selection bias at enrolment and at follow-up. Results: A total of 719 infants were enrolled and 581 (80.8%) and 499 (69.4%) were followed at 4 and 8 years, respectively. The prevalence of overweight/obesity was 9.3% and 36.9% at 4 and 8 years. No evidence of an association was found between vehicular traffic and being overweight/obese. Similarly, there was no evidence of an association between exposure to air pollutants and all other ponderal excess parameters. Conclusions: The study shows no association between exposure to vehicular traffic and exposure to pollutants on obesity related parameters such as BMI, blood lipids and abdominal adiposity during childhood. Overall evidence of air pollution being obesogenic remains limited.