Early life antibiotic exposure does not promote autism spectrum disorder

Jairia Dela Cruz
30 Aug 2018

Antibiotic exposure during the first year of life does not appear to contribute to an increased risk of developing autism spectrum disorder (ASD), according to a study.

“[The] findings should provide reassurance to concerned prescribers and parents,” given that antibiotics are the most frequently prescribed medications for children, the investigators said.

The study included 214,834 infants born in Manitoba, Canada, from 1998–2016. Of these, 94,024 (43.8 percent) received at least one course of antibiotics during the first year of life, while 2,965 were diagnosed with ASD at a mean age of 5.48 years.

Crude incidence rates of ASD were 1.46 per 1,000 person-years in the group exposed to antibiotics in early life and 1.59 per 1,000 person-years in the unexposed group. Cox proportional hazards regression analysis revealed no association between early life exposure to antibiotics and ASD risk (adjusted hazards ratio [HR], 0.93; 95 percent CI, 0.87– 1.00). [Int J Epidemiol 2018;doi:10.1093/ije/dyy162]

Likewise, the number of treatment course and cumulative duration of antibiotic exposure were not associated with the risk.

A sibling-cohort analysis (n=80,225 children; n=57,063 sibling pairs discordant in exposure status) accounting for the likelihood of unmeasured confounding due to familial and genetic factors confirmed the lack of association between early life antibiotic exposure and ASD risk (adjusted HR, 1.03; 0.86–1.23). Risk associations remained nonsignificant after stratifying by sex and region, and when exposure was examined by the number of courses, cumulative duration and antibiotic class.

Antibiotics may induce the development of ASD in children through disruption of the gut-brain axis, leading to microbiota changes, the investigators noted. [J Autism Dev Disord 2014;44:1117-1127; Microbiome 2017;5:24]

In previous studies, infants exposed to antibiotics perinatally have shown significant changes in both the diversity and the quantities of microbiota composition at 1 year of age. [Allergy Asthma Clin Immunol 2014;10:A31]

“On the contrary, we did not observe th[e] expected increase in ASD rates in children exposed to antibiotics in their first years of life. This could be attributed to the magnitude of microbiota changes being too small to impair neurodevelopment, or that a specific profile of microbiota changes is responsible for neurodevelopmental disorders,” the investigators explained.

“The complexity of gut microbiota and consequences following any changes make the association with childhood diseases a challenging one to investigate, and warrant further studies to examine such risk on both biological and population levels,” they added.

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