NYU Researchers Claim Early Exposure to Antibiotics Associated with Increase in Body Mass

New York University researchers using the Avon Longitudinal Study of Parents
and Children with data on more than 11,000 children have purportedly found
a consistent association between antibiotic exposure in the first six months
of life with “elevations in body mass index with overweight and obesity from
ages 10 to 38 months.” L. Trasande, et al., “Infant antibiotic exposures and
early-life body mass,” International Journal of Obesity, August 21, 2012 (online).

The researchers suggest that the administration of antibiotics during early
life, “a critical period for gut colonization,” may disrupt “ancient patterns of
intestinal colonization.” U.S. farmers since the late 1940s have apparently
given low-dose antibiotics to domesticated mammalian and avian species to
hasten weight gain with the understanding that “alterations in the microbiota
change ‘feed efficiency.’” Thus, the researchers explored the possibility of
similar effects in human children. According to lead researcher Leonardo
Trasande, “Microbes in our intestines may play critical roles in how we absorb
calories, and exposure to antibiotics, especially in early life, may kill off healthy
bacteria that influence how we absorb nutrients into our bodies, and would
otherwise keep us lean.” Confounders accounted for included parental body
mass index (BMI), smoking, breastfeeding, timing of food introduction, and
lifestyle variables, among others. The study was limited to the use of two
medications: antipyretics and eye ointment.

While exposures during the birth-6 month window were consistently associated
with elevations in body mass, exposure during the 6-14 month window
was not, and “[t]he pattern of association for exposure 15-23 months was less
clear.” Those in this exposure window “were significantly associated only with
elevated standardized BMI score at 7 years, but not with consistently elevated
scores in the interim.” The study found that “[a]t 38 months, children who
had been exposed to antibiotics during [the] earliest period had significantly
higher standardized BMI scores, and were 22% more likely to be overweight
than children who had not been exposed.”

While the researchers conclude that the study “reinforces concerns that early life antibiotic exposure may cause increases in body mass later in life,” they note that important limitations are presented by “multiple social, behavioral and biological factors” as well as parental recall regarding antibiotic usage. They call for additional research “to disaggregate the effect of early exposures to antibiotics from those occurring in the prenatal and perinatal periods, and to quantify the life-course implications for body mass and cardiovascular risks, at the population level.” See CommonHealth.wbur.org, August 2012.