Phthalates exposure and longitudinal trajectories of body composition and regional fat distribution in children: shifting towards "apple-shaped" body and the role of physical activity.

BACKGROUND: The effects of phthalate esters (PAEs) exposure on longitudinal changes in body composition and body fat distribution are not understood, especially in children. The study aimed to assess how PAEs influence the long-term changes in body composition (fat mass index (FMI), body fat percentage (BF%), fat-free mass index (FFMI), bone mineral density (BMD_Z), lean mass (LM) and total body water (TBW%)) and body regional fat distribution, and how physical activity moderate these effects. METHODS: We tracked 519 children in a child growth and development cohort from May 2017 to October 2020 in Xiamen city of China, measuring PAE metabolites at the outset and assessing body composition through bioelectrical impedance analysis at six visits. Generalized estimating equations were used for the relationship between PAEs and repeated body composition measurements. Group-based trajectory modeling and multinomial logistic regressions were employed to examine how PAEs exposure influenced the trajectories of body composition. Further, stratified analysis with an interaction term was used to investigate how physical activity influences such relationships. RESULTS: Children (8.62 years) presented significant correlations between mono-n-butyl PAEs exposure with the "largest" trajectory of FMI, BF% and FFMI, with the ORs of 1.69, 1.70 and 2.17, respectively (P < 0.05). Whereas exposure to mono-iso-butyl phthalate was negatively linked to the "largest" trajectory of LM (OR = 0.51, 95%CI = 0.28, 0.93). Most PAE metabolites were significantly related to the "largest" trajectory of BF% in the trunk and upper limbs (P < 0.05), but moderate-to-high physical activities could relieve the increased BMD trajectories caused by mono-2-ethylhexyl PAEs exposure (P for interaction = 0.023) and decrease regional BF% in the trunk and upper limbs. CONCLUSIONS: PAEs exposure was linked to larger trajectories of fat mass, BF% and BMD, a smaller LM trajectory, and fat accumulation in the trunk and upper limbs, suggesting an "apple-shaped" body. Physical activity help relieve the increased BMD driven by PAEs and fat buildup in the upper body related to PAEs.