Fewer antibiotics, less dysbiosis, less childhood asthma

Childhood asthma affects 8% of young Americans and Canadians. Its prevalence doubled in the second half of the 20^th century, but the trend seems to be reversing. Is this decline linked to a reduction in antibiotic prescription and to the resulting beneficial effects on the intestinal microbial community? To test this hypothesis, the authors analyzed government data on asthma diagnoses and antibiotic prescriptions in British Columbia (sidenote: Data from the BC PharmaNet government database, which collects data from all health centers in the province (database population: 4.7 million) )  (Canada), as well as the intestinal microbiota of 2,644 children participating in the Canadian CHILD Cohort Study (sidenote: Canadian CHILD Cohort Study Canadian Healthy Infant Longitudinal Development study, a prospective study of children recruited before birth between 2008 and 2012 ) .

Fewer antibiotics means less asthma

At population level, between 2000 and 2014, the incidence of asthma among one- to four-year-old children fell by 7.1% in absolute terms, from 27.3% to 20.2%, based on Canadian government data. In the same period, the prescription of antibiotics to children under the age of one decreased significantly (from 1,253.8‰ to 489.1‰). In 2014, one in three children (34.8%) was prescribed antibiotics at least once before the age of one, compared to two in three children (66.9%) in 2000. Statistical analysis shows a link between antibiotic prescription and asthma: the incidence of asthma increases by 24% with each 10% increase in antibiotic prescription. This trend observed at population level was also found at individual level in the CHILD cohort. After excluding children who had received antibiotics for respiratory problems, the diagnosis of asthma at five years of age was more frequent among children prescribed antibiotics before the age of one. Furthermore, the incidence of asthma increased with the number of prescriptions: 5.2% for no prescription, 8.1% for one, 10.2% for two and 17.6% for three or more.

Role of the microbiota

According to the authors, a dysbiosis of the intestinal microbiota in infants could explain the link between antibiotic exposure and childhood asthma. Children with asthma at five years of age showed less diversity in their gut microbiota at the age of one. This diversity decreased with the number of antibiotic treatments and the earlier the age of prescription (with a sharp reduction if taken before three months). The lower diversity was associated to a decrease in five key bacterial groups, particularly two species involved in the production of immunomodulating short-chain fatty acids. Therefore, the reduction of certain bacterial species may influence the development of children’s immune systems, making them susceptible to allergies. Hence the potential value of strategies aimed at maintaining the diversity of the microbiota after antibiotic use and the need for prudent use of antibiotics before the age of one.