Our asthma research program involves both exposure assessment and prevention components, and focuses on the relationship between exposure to indoor allergens and asthma prevalence and morbidity. We have worked with investigators at the CDC/NCHS to implement the allergen and asthma component of National Health and Nutrition Examination Survey (NHANES) 2005-2006. We collected bedroom dust, measured levels of common indoor allergens and endotoxin, assessed serum total and allergen-specific IgE, and determined asthma and allergy prevalence and morbidity in approximately 9000 individuals in the U.S. Analysis of this large data set will allow us to 1) estimate nationwide prevalence of indoor allergen and endotoxin exposures, 2) estimate nationwide prevalence of allergic sensitization to indoor, outdoor and food allergens, 3) estimate nationwide prevalence of allergic diseases, including asthma, and 4) investigate the complex relationships between allergen and endotoxin exposures, allergic sensitization and allergic diseases. NHANES 2005-2006 not only tested a greater number of allergens across a wider age range than prior studies, but also provided quantitative information on the extent of allergic sensitization and exposures to indoor allergens and endotoxin. The NHANES 2005-2006 data demonstrated that endotoxin levels were positively associated with asthma-related outcomes, especially wheezing. However, none of the observed associations were modified by participants age. We also examined indoor allergen levels in Mexican homes in a collaborative study. We found that exposure to indoor allergens was common in these homes; dust mite, mouse and cat allergens being the most commonly detected allergens. Consistent with our previous findings in the national surveys (National Survey of Lead and Allergens in Housing, NHANES 2005-2006), each allergen appeared to have a distinct set of predictors. Despite some population-specific differences, similar factors tended to predict elevated exposure levels to individual and multiple allergens across populations. In a randomized, controlled intervention study, we investigated whether education coupled with commercially available in-home test kits, which provide semi-quantitative information on residential allergen levels, influences compliance with recommended dust mite reduction strategies. Our results suggested that parents might become more motivated to participate in allergen reduction interventions when they could actually see results for themselves. In households that received the test kits, dust mite allergen levels were significantly reduced over time compared to control homes. This is the first study to demonstrate that the use of in-home test kits along with education may beneficially influence behaviors and attitudes towards dust mite reduction strategies and can help to reduce dust mite allergen levels in the home. We also used NHANES data from the survey cycles 1999 to 2004 to investigate exposure to individual environmental chemicals and selected mixtures in relation to the presence of antinuclear antibodies (ANA), a widely used biomarker of autoimmunity. This study showed several associations between chemical concentration and ANA positivity, but only the association in males exposed to triclosan remained statistically significant. Because ANA prevalence was significantly higher in females compared to males, we examined associations of reproductive and hormonal factors with ANA prevalence among female participants, in order to enhance understanding of the development of autoimmunity in women. As ANA prevalence was associated with parity, childbearing may play an important role in initial antigen stimulation or breaking tolerance to self-antigens. Since the NHANES data set allows for the investigation of many interesting relationships, we continue to investigate the complex relationships between allergen exposure, allergic sensitization, and disease in more detail. In addition to providing data on these relationships, the NHANES 2005-2006 will establish a second point-in-time estimate for evaluating allergen and endotoxin exposure trends in U.S. homes, first being established in the National Survey of Lead and Allergens in Housing, which we completed in collaboration with the Department of Housing and Urban Development. Our research will lead to a better understanding of the characteristics and predictors of residential indoor allergen and endotoxin exposures, which in turn provides insights into development of effective environmental intervention approaches for the management of allergic diseases such as asthma.
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