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Day Care Doesn't Protect Against Asthma

Findings Challenge 'Hygiene Hypothesis'

7 Million Kids U.S. Kids Have Asthma

Supporters of the hygiene hypothesis say it could help explain the dramatic increase in allergy and asthma in industrialized countries during a time when exposure to germs has declined.

Asthma is now the most common chronic disease of childhood, affecting close to 7 million children in the U.S., according to the American Lung Association.

Many studies examining the hygiene hypothesis have focused on day care attendance because children who go to day care tend to be exposed to more germs and infections.

Findings have been mixed, with some studies suggesting a protective role for day care attendance and others failing to show a benefit.

The new research is one of the largest studies ever to address the question, with some of the longest follow up.

But asthma specialist John Mastronarde, MD, tells WebMD that an even longer follow up would be needed to conclusively show that early day care attendance has no lasting impact on asthma risk.

Mastronarde directs the asthma center at Ohio State University Medical Center.

“This study adds another interesting piece to the puzzle, but I don’t see it as definitive,” he says.

He says it is increasingly clear that rather than being a specific disease with one specific cause, asthma is a heterogeneous disorder with many different triggers.

Asthma researcher Clare Ramsey, MD, agrees the new study is not definitive.

An assistant professor of medicine at the University of Manitoba, Ramsey co-wrote a 2005 review of the research, concluding that “the hygiene hypothesis is not likely to be the sole explanation for the ongoing asthma epidemic in industrialized nations.”

“Based on all the available data, I would agree that there is no substantial evidence that early day care should be recommended as a preventive strategy to the general public to reduce asthma,” she tells WebMD.

But she adds that the new study did not address the question of whether day care attendance protects children who are genetically predisposed to develop asthma, as previous studies have suggested.


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