Background: Changes in microbiota composition as a result of antibiotics use in early life has been proposed as a possible contributor in the aetiology of autism spectrum disorders (ASD). We aimed to examine the association between early life antibiotic exposure and risk of ASD.
Methods: This was a population-based cohort study which included all live births in Manitoba, Canada, between 1 April 1998 and 31 March 2016. We used administrative health data from the Manitoba Population Research Data Repository. Exposure was defined as having filled one or more antibiotic prescription during the first year of life. The main outcome was ASD diagnosis. Cox proportional hazards regression models were used to estimate the risk of developing ASD in the overall population and in a sibling cohort.
Results: Of all subjects in the cohort (n = 214 834), 94 024 (43.8%) filled an antibiotic prescription during the first year of life. During follow-up, 2965 children received an ASD diagnosis. Compared with children who did not use antibiotics during the first year of life, those who received antibiotics had a reduced risk of ASD [adjusted hazardz ratio (HR) 0.91, 95% confidence interval (CI) 0.84-0.99). Number of treatment courses and cumulative duration of antibiotic exposure were not associated with ASD. In the sibling-controlled analysis, early life antibiotic exposure was not associated with ASD (adjusted HR 1.03, 95% CI 0.86-1.23).
Conclusions: Our findings suggested no clinically significant association between early life antibiotics exposure and risk of autism spectrum disorders, and should provide reassurance to concerned prescribers and parents.