title: Antibiotic exposure in infancy and risk of being overweight in the first 24 months of life.
abstract: OBJECTIVE
  Antibiotics have direct effects on the human intestinal microbiota, particularly in infancy. Antibacterial agents promote growth in farm animals by unknown mechanisms, but little is known about their effects on human weight gain. Our aim was to evaluate the impact of antibiotic exposure during infancy on weight and height in healthy Finnish children.
  
  
  METHODS
  The population-based cohort comprised 6114 healthy boys and 5948 healthy girls having primary care weight and height measurements and drug purchase data from birth to 24 months. BMI and height, expressed as z-scores at the median age of 24 months (interquartile range 24 to 26 months), were compared between children exposed and unexposed to antibiotics using analysis of covariance with perinatal factors as covariates.
  
  
  RESULTS
  Exposed children were on average heavier than unexposed children (adjusted BMI-for-age z-score difference in boys 0.13 SD [95% confidence interval 0.07 to 0.19, P < .001] and in girls 0.07 SD [0.01 to 0.13, P < .05]). The effect was most pronounced after exposure to macrolides before 6 months of age (boys 0.28 [0.11 to 0.46]; girls 0.23 [0.04 to 0.42]) or >1 exposure (boys 0.20 [0.10 to 0.30]; girls 0.13 [0.03 to 0.22]).
  
  
  CONCLUSIONS
  Antibiotic exposure before 6 months of age, or repeatedly during infancy, was associated with increased body mass in healthy children. Such effects may play a role in the worldwide childhood obesity epidemic and highlight the importance of judicious use of antibiotics during infancy, favoring narrow-spectrum antibiotics.
authors.affiliation: Department of Pediatrics, School of Medicine, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland; Department of Pediatrics, Kuopio University Hospital, Kuopio, Finland; antti.saari@kuh.fi.
authors.forename: Antti
authors.initials: A
authors.lastname: Saari
authors.affiliation: Department of Research, Social Insurance Institution, Turku, Finland;
authors.forename: Lauri J
authors.initials: LJ
authors.lastname: Virta
authors.affiliation: Department of Pediatrics, Kuopio University Hospital, Kuopio, Finland;
authors.forename: Ulla
authors.initials: U
authors.lastname: Sankilampi
authors.affiliation: William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom; and.
authors.forename: Leo
authors.initials: L
authors.lastname: Dunkel
authors.affiliation: Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Saxen
mesh_terms: D000900:Anti-Bacterial Agents / Q000009:adverse effects* / Q000627:therapeutic use*; D001827:Body Height / Q000187:drug effects; D015992:Body Mass Index; D015331:Cohort Studies; D005260:Female; D005387:Finland; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D018942:Macrolides / Q000009:adverse effects / Q000627:therapeutic use; D008297:Male; D050177:Overweight / Q000139:chemically induced* / Q000453:epidemiology; D012306:Risk; D012737:Sex Factors; D013223:Statistics as Topic; D015430:Weight Gain / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides
keywords: BMI; anti-bacterial agents; antibiotics; body weight; growth; height; microbiota; overweight; weight