Effect modifications of parents' age at childbirth on association between ambient particulate matter and children obesity.

Background: There is limited evidence regarding the modifying effects of parents' age at childbirth on the relationship between air pollution and obesity in plateau areas. This study aimed to explore the association between particulate matter (PM) and child obesity, specifically investigating whether parents' age at childbirth could modify this relationship in the Tibetan plateau, China.

Methods: Satellite-based random forest models were used to estimate the concentrations of PM (particulate matter with aerodynamic diameters ≤ 2.5 μm), PM (particulate matter with aerodynamic diameters between 2.5 μm and 10 μm), and PM (particulate matter with aerodynamic diameters ≤ 10 μm). Linear and logistic regression models were employed to assess associations between PM exposure and obesity indicators, and effect estimates of PM across different particle sizes were compared.

Results: The study comprised 2,015 children under five years old. Postnatal exposure to PM was positively associated with overweight and obesity (OWO), waist-to-hip ratio (WHR) and body mass index (BMI). Among these pollutants, PM exhibited the strongest association with BMI and OWO, whereas PM showed the strongest association with WHR. An interquartile range (IQR) increase in PM (5.67 µg/m), PM (5.25 µg/m), and PM (11.06 µg/m) was positively associated with OWO (odd ratio [OR] for PM = 1.52, 95% confidence interval [CI] for PM = 1.24 to 1.85; OR for PM = 1.50, 95% CI for PM = 1.19 to 1.88; OR for PM = 1.56, 95% CI for PM = 1.25 to 1.96), respectively. Stratified analysis by parents' age at childbirth indicated that the effects of PM on obesity indicators were more pronounced in the advanced age group.

Conclusions: Long-term exposure to PM was positively associated with OWO, WHR, and BMI. Our findings also underscore the importance of examining the effects of ambient PM exposure on OWO, particularly in parents of advanced age at childbirth.