Antibiotic Use in the First 2 Years of Life Is Related to Longitudinal BMI Trajectories From 0 to 18 years: A Prospective Cohort Study

BACKGROUND/OBJECTIVE: Antibiotic exposure by 2 years is linked to increased childhood overweight/obesity risk, mainly in cross-sectional studies. Few longitudinal studies exist in high-risk populations, and none examined BMI trajectories up to 18 years. Our study is the first to investigate the association between early antibiotic exposure and BMI trajectories in a high allergy-risk cohort. METHODS: We analysed data from 428 participants in the Melbourne Atopy Cohort Study from birth to 18 years. Antibiotic use < 2 years was categorized as "ever versus never" and according to seven antibiotic classes. Number of courses (7 days) and the spectrum of antibiotics (broad versus narrow) were defined for each antibiotic class. Logistic regression models estimated associations between antibiotic use (any/specific), courses (0, 1, 2, and ≥ 3), and previously defined BMI trajectories from 4 weeks to 18 years: very low catch-up, low average, stable average (reference), average increasing to very high (AIVH), and persistently high (PH). RESULTS: We found consistent evidence of a relationship between antibiotic exposure by 2 years and increased risk of belonging to AIVH and PH trajectories, with magnitudes of effect differing by antibiotic spectrum and frequency. Notably, exposure to ≥ 3 courses of broad-spectrum antibiotic was associated with the AIVH (aOR = 3.36 [95% CI: 1.03, 10.87]) and PH trajectories (aOR = 3.29 [95% CI: 1.03, 10.53]). CONCLUSION: These findings may have important clinical implications, but further large-scale studies are required.