Vol.:(0123456789) 1 3 World Journal of Pediatrics https://doi.org/10.1007/s12519-018-00223-1 ORIGINAL ARTICLE Antibiotic use in early childhood and risk of obesity: longitudinal analysis of a national cohort Dervla Kelly 1  · Alan Kelly 1  · Tom O’Dowd 1  · Catherine B. Hayes 1 Received: 20 June 2018 / Accepted: 20 December 2018 © Children’s Hospital, Zhejiang University School of Medicine 2019 Abstract Background Taking oral antibiotics during childhood has been linked with an increased risk of childhood obesity. This study assessed any potential association in number of courses of antibiotics taken between 2–3 and 4–5 years of age and body mass trajectory up to age 5. Methods The study was a secondary analysis of 8186 children and their parents from the infant cohort of the Irish National Longitudinal Study of Children. Antibiotic use was measured by parental recall between ages 2–3 and 4–5. Longitudinal models described the relationship between antibiotic exposure and body mass index (BMI) standard deviation scores and binary outcomes, and examined interactions between covariates, which included socioeconomic status, diet assessed by food frequency questionnaires and maternal BMI. Results Any antibiotic usage between 2 and 3 years did not predict risk of overweight or obesity at age 5. Four or more courses of antibiotics between 2 and 3 years were independently associated with obesity at age 5 (odds ratio 1.6, 95% con- fdence interval 1.11–2.31). Efect size was modest (coefcient + 0.09 body mass SD units, standard error 0.04, P = 0.037). Maternal BMI modifed the relationship: ≥ 4 courses of antibiotics between 2 and 3 years were associated with a + 0.12 body mass SD units increase in weight at age 5 among children of normal-weight mothers (P = 0.035), but not in children of overweight mothers. Conclusions Number of antibiotic courses, rather than antibiotic use, may be an important factor in any link between early antibiotic exposure and subsequent childhood obesity. Research is needed to confrm diferential efects on babies of normal versus overweight/obese mothers independent of socioeconomic factors. Keywords Antibiotics · Body mass index · Early childhood · Infants · Obesity Introduction Childhood obesity remains a major public health concern in western countries, including Ireland. It is a strong pre- dictor of adult obesity [1]. Obesity is now recognized as a clinical condition [2] afecting all body systems and a major contributor to chronic diseases including type 2 diabetes mellitus, cardiovascular disease and cancer morbidity and mortality [3–5]. Quality of life may be severely impaired as evidenced by psychological complications such as low self-esteem and depression [6, 7]. Obesity is a multifactorial condition and antibiotic consumption in childhood has been suggested as a potential contributing factor. Antibiotic prescribing is common in young children espe- cially for respiratory infections. Experimental evidence has shown that antibiotics disrupt the gut microbiota and these changes could disrupt metabolic processes. It is, therefore, plausible that agents modulating the microbiota, such as antibiotics, may afect body weight [8, 9] and there is con- cern that early childhood is a particularly vulnerable period when such efects may have long-term consequences [10]. The degree of infuence of antibiotics on metabolism depends in theory on two determinants: (1) frequency of Alan Kelly: RIP, 5th October 2015. Dublin, Ireland. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12519-018-00223-1) contains supplementary material, which is available to authorized users. * Dervla Kelly dkelly23@tcd.ie 1 Department of Public Health and Primary Care, Trinity College Dublin, Russell Center, Tallaght Cross, Dublin 24, Ireland