Tuesday, 21 October 2014

Antibiotics and childhood obesity: a weighty correlation

It's been a few weeks since the publication of the paper by L. Charles Bailey and colleagues [1] correlating early multiple exposure to broad spectrum antibiotics with obesity in infancy. On purpose I've left it a while before talking about this research so as to let the scientific dust settle a little and get a flavour for some of the discussions about this research (see here and see here).
You're a true vulgarian, aren't you?

A few details about the Bailey study first:

  • Looking at the electronic records for a large cohort of children (~65,000), researchers picked out "Treatment episodes for prescribed antibiotics" based on prescription data before the age of 2 years.
  • Anthropometric (growth) data was also determined from visits to healthcare providers between the ages of 2 and 5 years and compared with body mass index (BMI) norms derived from a large US-based survey, NHANES.
  • Results: "Sixty-nine percent of children were exposed to antibiotics before age 24 months" with a rough average of 2 antibiotic prescriptions per child. For those who received 4 or more courses of antibiotics, the risk of obesity during early childhood was slightly elevated (11%) compared with those receiving fewer courses.
  • The authors specifically focused on broad spectrum antibiotics as being correlated with infant weight issues; antimicrobials acting against a broad range of bacteria rather than more targeted pharmaceutics.
  • They concluded: "Repeated exposure to broad-spectrum antibiotics at ages 0 to 23 months is associated with early childhood obesity". That being said, they also noted that various other factors seemed to correlate with infant obesity including: "Steroid use, male sex, urban practice, public insurance, Hispanic ethnicity, and diagnosed asthma or wheezing".
  • I'm also minded to pull in a few other findings which did not get so many media headlines such as the reporting that at 4 years of age, 15% of the cohort were found to be obese and 33% overweight (source here).

The Bailey results are interesting insofar as the association being made between early antibiotic use and obesity but, as always, a little caution needs to be applied before reading too much into the findings. I note the BBC coverage of this article mentions limitations: "they were not able to look at the children's weight or exercise regimes" so correlation not necessarily being the same as causation comes into play. I might also add that whilst antibiotic stewardship is still a developing area, many/most antibiotic prescriptions are not just given willy-nilly as any parent with a young child suffering from an ear infection for example, will probably be able to attest.

I have kinda talked around this area of antibiotics and weight before on this blog (see here) and the implication that antibiotics, broad spectrum, by their very nature have a pretty profound effect on the trillions of bacterial beasties which inhabit places like the gastrointestinal (GI) tract. Carl Zimmer's post on swallowing a grenade (not literally) is a good starting point. The idea being that as well as helping digest our food, said bacteria (whether individual strains or through a more collective action) might also be able to influence a variety of issues like energy homoeostasis, weight management and even our risk of disease (see here and see here). If I take you back to some work looking at a particular bacterium called Akkermansia muciniphila you might get a flavour for this possible connection with weight in mind (at least in rodents).

I'm going to finish with another quote included with the BBC report on the Bailey findings. It comes from an independent commentary of the paper and sums up some important issues arising from reading this work:

"It would be a concern if parents took from this that they ought to be reluctant to allow antibiotic use in their children. The key risk factors for childhood obesity are over-consumption of high energy, nutrient-poor foods and lack of exercise."

Whilst I would perhaps suggest that 'energy in - energy out' is too simplistic an explanation of weight management issues (see here) I would agree that under the right circumstances, antibiotics still make a valuable contribution to the medicines cabinet, and obesity is, very much, a multi-faceted condition.

Music... Stevie Wonder and Superstition.

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[1] Bailey LC. et al. Association of Antibiotics in Infancy With Early Childhood Obesity. JAMA Pediatr. 2014. 29 Sept.

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ResearchBlogging.org Bailey LC, Forrest CB, Zhang P, Richards TM, Livshits A, & DeRusso PA (2014). Association of Antibiotics in Infancy With Early Childhood Obesity. JAMA pediatrics PMID: 25265089