Published: Sep 29, 2014
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By Michael Smith, North American Correspondent, MedPage Today
Children exposed repeatedly to antibiotics in their first 2 years of life were more likely to be obese later in childhood, researchers said.
Children with four or more courses of antibiotics were 11% more likely than others to become obese, according toCharles Bailey, MD, PhD, of the Children’s Hospital of Philadelphia, and colleagues.
But the effect was restricted to broad-spectrum drugs, suggesting that more narrower antibiotic selection might modify the risk, Bailey and colleagues reported online in JAMA Pediatrics.
Because obesity is multifactorial, the authors argued, cutting its prevalence means “identifying and managing multiple risk factors whose individual effects may be small but modifiable.”
In 2011, the Institute of Medicine identified several such factors, including the mother’s pre-pregnancy body mass index, physical activity, and sleep duration. But one “emerging factor,” Bailey and colleagues noted, was the role played by microbial populations in the intestine, which can be affected by antibiotics.
To examine the issue, the investigators looked at a cohort of 64,580 children seen from 2001 to 2013 in a network of primary care practices in Philadelphia and the surrounding region.
Using an electronic health records system shared by all the practices, the researchers looked at all children who had annual visits from birth through 23 months, as well as at least one more visit from months 24 through 59.
They looked at recorded antibiotic prescriptions in the first 2 years of life and used Cox proportional hazards models to look for associations with obesity in the following 3 years.
For this analysis, children were said to be obese if they were at or above the 95th percentile of the 2000 National Health and Nutrition Examination Survey (NHANES) growth norms. They were considered overweight if the percentile was at least 85 but less than 95.
Some 69% of the children in the cohort had at least one exposure to antibiotics before 24 months, with an average of 2.3 episodes per child, the investigators found.
Overall, 62% of children had at least one exposure to a narrow-spectrum antibiotic and 41% were given broad-spectrum medications. Only 14% of children younger than 6 months were prescribed antibiotics, but on each of the following 6-month periods, the rate ranged from 40% to 45%, Bailey and colleagues reported.
Children who were given antibiotics were similar at the time of exposure in terms of weight-for-length to children who did not get the drugs.
But cumulative exposure to antibiotics was associated with later obesity: the rate ratio for children with at least four episodes was 1.11, with a 95% confidence interval from 1.02 to 1.21, compared with no medications.
The effect was greater for broad-spectrum antibiotics, where the rate ratio was 1.16, with a 95% confidence interval from 1.06 to 1.29, but there was no significant effect for narrow-spectrum drugs.
Getting broad-spectrum drugs early was also associated with obesity, Bailey and colleagues found. For children who got such medications in the first 6 months of life, the rate ratio was 1.11 (95% CI 1.03-1.19); it was 1.09 (95% CI 1.04-1.14) when drugs were given in the second 6 months.
Primary source: JAMA Pediatrics