Children attending day care at an early age are more likely to breathe easy later, according to a new study of wheezing among children in Manchester, England.

Babies who began day care when they were 6 to 12 months old were about half as likely as those who did not attend day care to develop a “wheeze” by age 5, a possible indicator of asthma, scientists report in the September Journal of Allergy and Clinical Immunology.

“I think it strengthens the case that day care may be protective against asthma,” comments Anne Wright, an expert in epidemiology of childhood asthma at the University of Arizona College of Medicine in Tucson.

But the findings are still too preliminary to serve as parenting advice, cautions study coauthor Angela Simpson, a respiratory physician at the University of Manchester. “We’re not trying to tell parents what to do with their children based on this,” she says.

The results could reinforce an idea called the “hygiene hypothesis,” which suggests that rises in childhood allergy and asthma rates in developed countries such as the United Kingdom are partly due to excessive hygiene. With less exposure to environmental bacteria and viruses, the theory goes, infants’ immune systems learn to attack the wrong targets, triggering allergic reactions and sometimes asthma.

The study only shows the connection between attending day care and wheezing rates without proving why the nursery reduces the chance of developing wheezing. But Wright says that in light of previous research, “to me it seems to have something to do with microbial exposure.”

Previous studies have shown that exposure to day care lowers children’s chances of developing allergies. But results for wheezing and asthma, which can be triggered by allergies, had been inconsistent.

In the new study, children who did not attend day care had otherwise healthy lung function, Wright notes, suggesting that the wheezing is indeed due to an immune response rather than a problem with the children’s airways.

But, Simpson adds: “This doesn’t tell us what within the nursery is the protective factor. We assume that it’s the bacteria in the nursery, but it might be something else.”

The study only shows the connection between attending day care and wheezing rates without proving why the nursery reduces the chance of developing wheezing. But Wright says that in light of previous research, “to me it seems to have something to do with microbial exposure.”

Simpson and her colleagues tracked the respiratory and allergy health of 952 children, recording parent-reported incidents of wheezing and performing lung function tests. Children who entered day care before 6 months of age actually had a higher chance of developing a temporary wheeze early in life, but were still less likely to have a lasting wheeze by age five than kids who never attended day care.

“Because of our genetic makeup, some children will benefit more from going to nursery than others,” Simpson notes. Finding the genetic factors that influence which children will get a health benefit from early exposure to a nursery will be the next step in their research, she says.

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