Prenatal particulate air pollution exposure and body composition in urban preschool children: Examining sensitive windows and sex-specific associations

Abstract

Background Evolving animal studies and limited epidemiological data show that prenatal air pollution exposure is associated with childhood obesity. Timing of exposure and child sex may play an important role in these associations. We applied an innovative method to examine sex-specific sensitive prenatal windows of exposure to PM2.5 on anthropometric measures in preschool-aged children. Methods Analyses included 239 children born ≥37 weeks gestation in an ethnically-mixed lower-income urban birth cohort. Prenatal daily PM2.5 exposure was estimated using a validated satellite-based spatio-temporal model. Body mass index z-score (BMI-z), fat mass, % body fat, subscapular and triceps skinfold thickness, waist and hip circumferences and waist-to-hip ratio (WHR) were assessed at age 4.0±0.7 years. Using Bayesian distributed lag interaction models (BDLIMs), we examined sex differences in sensitive windows of weekly averaged PM2.5 levels on these measures, adjusting for child age, maternal age, education, race/ethnicity, and pre-pregnancy BMI. Results Mothers were primarily Hispanic (55%) or Black (26%), had ≤12 years of education (66%) and never smoked (80%). Increased PM2.5 exposure from 8–17 and 15–22 weeks gestation was significantly associated with increased BMI z-scores and fat mass in boys, but not in girls. Higher PM2.5 exposure from 10–29 weeks gestation was significantly associated with increased WHR in girls, but not in boys. Prenatal PM2.5 was not significantly associated with other measures of body composition. Estimated cumulative effects across pregnancy, accounting for sensitive windows and within-window effects, were 0.21 (95%CI=0.01–0.37) for BMI-z and 0.36 (95%CI=0.12–0.68) for fat mass (kg) in boys, and 0.02 (95%CI=0.01–0.03) for WHR in girls, all per μg/m3 increase in PM2.5. Conclusions Increased prenatal PM2.5 exposure was more strongly associated with indices of increased whole body size in boys and with an indicator of body shape in girls. Methods to better characterize vulnerable windows may provide insight into underlying mechanisms contributing to sex-specific associations.

Maternal and early‐life area‐level characteristics and childhood adiposity: A systematic review

“…Two duplicate studies conducted by the same lead authors using the same dataset were identified, one study was retained as environmental measures were included in the fully adjusted model, whereas they were not in the other study. In total, eight studies were included in the narrative synthesis . Four studies were based in the United States, one each in Canada, Denmark, England, and South Korea.…”

“…Four studies recruited women during pregnancy, one study recruited shortly after birth, one study used a combination of the two, one study recruited 9 months after birth, and one study recruited children through schools . The recruitment rate varied between 12% and 78% (mean 51%) and was not presented in two studies . The percentage of the recruited sample who participated at each outcome time‐point varied between 22% and 83% (mean 60%).…”

“…The eight studies varied in terms of the timings of exposure and outcome measurement. Two studies had only one time‐point for exposure, and four had only one time‐point for the outcome . Five studies assessed the average exposure over the entire pregnancy, four across the first year of life, and two in the preconception period, defined as 3 months prior to conception .…”

“…There were a total of eight anthropometric outcomes examined across the eight studies (BMI z‐score, weight‐for‐age z‐score, overweight or obesity based on BMI cut‐off, obesity based on BMI cut‐off, fat mass, waist‐to‐hip‐ratio, skinfold thickness, and waist circumference), with four studies examining more than one outcome . All outcomes were measured by research assistants, school nurses, or GPs, with the exception of one study, where the measurer of height and weight was “undefined” for 35% of the sample .…”

“…All outcomes were measured by research assistants, school nurses, or GPs, with the exception of one study, where the measurer of height and weight was “undefined” for 35% of the sample . BMI was the most common outcome and was present in five studies (four used age‐ and sex‐adjusted z‐scores, one did not). An age‐ and sex‐ adjusted cut‐off for overweight/obesity was used in four studies, and fat mass was assessed in two studies .…”