Study debunks 'hygiene hypothesis' that early exposures boost immune response
WEDNESDAY, Sept. 9 (HealthDay News) -- Early day care, so the story goes, exposes kids to more germs and illnesses at an early age, thereby protecting them from asthma and allergies later on.
Scientists call it the ''hygiene hypothesis," but a new study casts doubt on its existence and finds early infections have no effect on asthma and allergy rates at age 8.
An unexplained increase in asthma among children in both industrialized countries and developing nations has scientists searching for ways to reduce the disease. In the United States, asthma affects nearly 5 million children and is the most common serious chronic childhood disease, according to the American Academy of Allergy, Asthma & Immunology.
Dutch researchers followed more than 3,600 children from birth through 8 years, noting their daycare use and health problems, such as wheezing. Those who started daycare early were twice as likely to experience wheezing in their first year as those who didn't attend daycare.
By age 5, however, the early daycare kids -- who started from birth to age 2 -- had less wheezing than the kids who didn't go, the researchers found.
But three years later, the discrepancy disappeared. "We found no evidence for any protection for asthma, allergy and airway hyper-responsiveness at 8 years," said Dr. Johan C. de Jongste, professor of pediatric respiratory medicine at Erasmus University Medical Center in the Netherlands, who led the study.
The researchers examined annual parental reports that asked about symptoms. Other assessments included blood tests to measure IgE, antibodies typically elevated in a person with allergies. They tested for lung function and hyper-responsiveness of the airways, and they controlled for such factors as a mother's allergies.
Would the results for Dutch children hold in the United
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