Early-Life Antibiotic Exposure and the Risk of Overweight and Obesity in Children

Background Early antibiotic exposure has been associated with increased weight gain and obesity in children. However, evidence associating the timing of antibiotic exposure to overweight and obesity is limited. Objectives The study explores whether the timing of early-life antibiotics or cumulative exposure is associated with childhood overweight and obesity. Methods This population-based cohort study included 33 095 children with 595 213 weight and height measurements linked to medical records and comprehensive national registers. Vaginally delivered children born in Northern Finland between the years 2007–2018 were followed until the end of 2019. Exposures included antibiotic exposure during the year before pregnancy, during pregnancy, in the perinatal period, and within the first 24 months of life. The primary outcomes were body mass index-for-age z-score (zBMI) at 24 months of age and the cumulative incidence of overweight and obesity up to 12 years of age. Analyses used linear mixed models and Cox hazard regression models adjusted for multiple covariates. Results Antibiotic exposure before pregnancy, during pregnancy, or in the perinatal period was not associated with subsequent overweight or obesity in children. In contrast, exposure during the first 24 months of life was linked to a higher zBMI at two years of age (mean difference in zBMI: 0.067 [95% CI, 0.041–0.094]) compared to unexposed children, after adjusting for covariates. Long-term analysis revealed an adjusted hazard ratio (HR) of 1.09 (95% CI 1.04–1.13) for overweight and 1.20 (95% CI, 1.10–1.31) for obesity. Conclusion Antibiotic exposure during the first two years of life was found to be associated with childhood overweight and obesity. No similar associations were observed for exposure before or at birth. Interventions aiming to reduce obesity-related effects should focus on minimizing early-life antibiotic use within the first two years of life.