Lately, I feel that it’s hard to avoid discussions of the microbiome. If you have managed to steer clear, a primer: the microbiome is the genetic material of all the bacteria, fungi, etc, which live in your gut. They are thought to be crucial in regulating your immune response and helping digestion; variations in the microbiome are linked to all kinds of health outcomes – obesity, digestive health, immune functioning, allergies. People go to lengths to improve their microbiome, including various supplements (i.e. probiotics) and more extreme measures (i.e. fecal transplants).
The microbiome of infants is initially colonized by their mother, both during birth and shortly after. “Quality” microbiome (it’s some what unclear what that means) is thought to be linked to better health outcomes including, among other things, lower allergy rates.
Which brings me to the New in Data topic here. Gut bacteria is known to be affected by antibiotics. Antibiotics kill bacteria – good and bad – and taking antibiotics can affect your microbiome. This is why you’ll sometimes get diarrhea on antibiotic treatment, and why doctors will sometimes prescribe probiotics or suggest you eat yogurt to offset.For infants, the same is true, and because infants are still developing, this raises concerns about long-term impacts.
New evidence, in JAMA Pediatrics, suggests that antibiotic treatment early in life increases allergies later on. The authors of this paper use data on almost 800,000 children and compare those who are prescribed antibiotics within their first six months to those who are not. They find the kids who got antibiotics early on are more likely to develop allergies. For example: those who got penicillin were 1.3 times as likely to have any allergy later. This seems to apply to all antibiotic types, and to all kinds of allergies (food, eczema, etc). The authors also show the risk goes up with each different type of antibiotic the baby takes.
How sure are we this is causal? That is, how sure are we that it is the antibiotics causing the allergies, rather than some third factor causing both? Certainly it is possible that something else increases both the need for antibiotics and the development of allergies; that’s hard to rule out with data like this. But understanding the possible mechanism – through the microbiome – does help strengthen the case for causality. As does the large sample and the authors ability to adjust for a lot of other factors that might matter (prematurity, for example).
Does this mean you should avoid antibiotics if your baby really needs them? No, of course not. But: it is well known that antibiotics are over-prescribed for infants and children and there are many cases where watchful waiting is an alternative. This evidence suggests that approach might have additional long term benefits.
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