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