Day Care Attendance Before Age 3 Months May Cut Asthma Risk for Some Children
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Reviewed By Louise Chang, MD
Oct. 18, 2007 -- Attending day care from early infancy may help protect high-risk children from developing asthma, new research suggests.
Regular day care attendance by 3 months of age was linked to lower levels of immunoglobulin E (IgE) antibodies in the University of Arizona study, but the association was seen only among children whose mothers had asthma or had positive skin tests for allergies.
IgE antibodies trigger the inflammatory responses that cause allergies and related asthma.
Researchers found that the IgE levels of children who started day care in early infancy remained low for at least the first three years of life.
The findings add support to the 'hygiene hypothesis' suggesting that early exposure to germs from different environments helps protect against allergies and asthma caused by allergic responses, researcher Anne L. Wright, PhD, tells WebMD.
"This study doesn't prove cause, but it adds to the evidence suggesting a protective effect by linking day care to this early predictor of asthma risk," she says.
Early Day Care Exposure Is Key
Asthma is the most common chronic disorder in childhood, affecting an estimated 6.2 million children in the U.S. under the age of 18, according to the American Lung Association.
In the study, the researchers examined the timing of day care exposure and the specific aspects of exposure that might influence a child's risk of developing allergic asthma.
They found that entering day care before the age of 3 months was associated with decreased IgE levels three years later in high-risk children (those with mothers who had asthma or allergies), but entering day care later in infancy or childhood was not protective.
The finding supports the idea of a "critical window of vulnerability" during which exposures influence the developing immune system, Wright says.
Being outside the home seemed to be a more important predictor of lower IgE levels later in life than the number of other children a child was exposed to.
This finding led the researchers to speculate that regular exposure to germs from two separate environments may play a greater role in immune response than early exposure to other children.
The study is published in the latest issue of the Journal of Allergy and Clinical Immunology.
Longer Follow-up Needed
Allergist David Tanner, MD, of the Atlanta Allergy & Asthma Clinic, calls the findings interesting but preliminary.
"The unanswered question is, 'What happens to these kids five years later?'" he says. "This study assumes that [lower IgE levels] correlate with some degree of protection against developing allergies later on."
Tanner advises parents of high-risk children to avoid day care early on if possible because of the known link between day care and an increased risk for viral infections.
"In the long run day care may protect against asthma, but we can't really say that yet," he says. "What we can say is that young children with a family history of asthma or who have already experienced wheezing with a viral infection will have more viral infections if they are in day care."
SOURCES: Rothers, J. Journal of Allergy and Clinical Immunology, October 2007; online edition. Anne L. Wright, PhD, Arizona Respiratory Care Center, University of Arizona. David Tanner, MD, allergist, Atlanta Allergy and Asthma Clinic. American Lung Association, Asthma and Children Fact Sheet, August 2006. Ball, T. New England Journal of Medicine, Aug.24, 2000; vol 343: pp 538-543.
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