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Members A-Topic to Consider: Atopy's role in asthma.
Asthma cases attributable to atopy: Results from the Third National Health and Nutrition Examination Survey
Samuel J. Arbes, Jr, DDS, MPH, PhD,a Peter J. Gergen, MD, MPH,b Ben Vaughn, MS,c and Darryl C. Zeldin, MDa Research Triangle Park and Chapel Hill, NC, and Bethesda, Md
Atopy is the genetic tendency to develop classic allergic diseases - atopic dermatitis, allergic rhinitis (hay fever), and asthma. Atopy involves the ability to produce IgE (the allergic antibody) in response to common environmental proteins such as house dust mite, grass pollen, and food allergens. It is a known risk factor for asthma. In fact, it has become common to describe asthma as an atopic disease. A theory has developed in which allergen exposure produces atopic sensitization and repeated exposure leads to symptoms of asthma through the development of airway inflammation, bronchial hyperresponsiveness, and reversible airflow obstruction. The importance of atopy is most widely accepted for asthma in children. However, the true percentage of asthma cases due to atopy is the subject of debate.
What if we have over-played the significance of atopy in asthma? Could we have under-recognized other possible causes for the development of asthma?
A study published in this month's The Journal of Allergy and Clinical Immunology used data from the Third National Health and Nutrition Examination Survey (NHANES III) to estimate the percentage of U.S. asthma cases due to atopy and look closely at associations between allergen-specific skin tests and asthma incidence. The authors found that about half of the current asthma cases in the US population were attributable to atopy. Of the 10 allergens investigated, only cat, Alternaria (a mold), and white oak showed a clear link with asthma. A positive response to cat accounted for the highest percentage of asthma cases (29.3%). This suggests that if atopy could be prevented or reversed, or its effect on asthma blocked, then a large percentage of asthma cases in the US population could be prevented. On the other hand, perhaps atopic asthma research has come at the expense of nonatopic asthma research. This study found that 1/3 to1/2 of the asthma cases apparently had a nonatopic etiology, highlighting the need for research into nonatopic causes of asthma. To significantly reduce the burden of asthma in the population, asthma research needs to address the causes of and interventions for both atopic and nonatopic asthma.
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