Individual and Joint Effects of Early-Life Ambient PM2.5 Exposure and Maternal Prepregnancy Obesity on Childhood Overweight or Obesity

Abstract

Background:Although previous studies suggest that exposure to traffic-related pollution during childhood increases the risk of childhood overweight or obesity (COWO), the role of early life exposure to fine particulate matter (aerodynamic diameter <2.5μm; PM2.5) and its joint effect with the mother's prepregnancy body mass index (MPBMI) on COWO remain unclear.Objectives:The present study was conducted to examine the individual and joint effects of ambient PM2.5 exposures and MPBMI on the risk of COWO.Methods:We estimated exposures to ambient PM2.5 in utero and during the first 2 y of life (F2YL), using data from the U.S. Environmental Protection Agency’s (EPA's) Air Quality System matched to residential address, in 1,446 mother–infant pairs who were recruited at birth from 1998 and followed up prospectively through 2012 at the Boston Medical Center in Massachusetts. We quantified the individual and joint effects of PM2.5 exposure with MPBMI on COWO, defined as the child's age- and sex-specific BMI z-score ≥85th percentile at the last well-child care visit between 2 and 9 y of age. Additivity was assessed by estimating the reduced excess risk due to interaction.Results:Comparing the highest and lowest quartiles of PM2.5, the adjusted relative risks (RRs) [95% confidence intervals (CIs)] of COWO were 1.3 (95% CI: 1.1, 1.5), 1.2 (95% CI: 1.0, 1.4), 1.2 (95% CI: 1.0, 1.4), 1.3 (95% CI: 1.1, 1.6), 1.3 (95% CI: 1.1, 1.5) and 1.3 (1.1, 1.5) during preconception; the first, second, and third trimesters; the entire period of pregnancy; and F2YL, respectively. Spline regression showed a dose–response relationship between PM2.5 levels and COWO after a threshold near the median exposure (10.46μg/normalm3–10.89μg/normalm3). Compared with their counterparts, children of obese mothers exposed to high levels of PM2.5 had the highest risk of COWO [RR≥2.0, relative excess risk due to interaction (RERI) not significant].Conclusions:In the present study, we observed that early life exposure to PM2.5 may play an important role in the early life origins of COWO and may increase the risk of COWO in children of mothers who were overweight or obese before pregnancy beyond the risk that can be attributed to MPBMI alone. Our findings emphasize the clinical and public health policy relevance of early life PM2.5 exposure. https://doi.org/10.1289/EHP261

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%).…”

“…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 . Three studies investigated trimester‐specific measures, including two studies that assessed the exposure in each trimester, and one study that assessed exposure in the third trimester only …”

“…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 . The following outcomes were assessed in only one study: waist‐to‐hip ratio; waist circumference and skinfold thickness; weight‐for‐age (ie, no height adjustment) …”

“…In addition to the potential bias arising from low response rates from specific subgroups, five of the included studies had attrition rates above 20%. Little to no effort was made to address the potential bias related to attrition or missing data, with Hawkins et al using survey‐derived weights and Fleisch et al imputing missing values for child ethnicity based on maternal ethnicity.…”