Indoor Allergens And Asthma

National Institute Of Environmental Health Sciences

Investigators

Linked publications, trials & patents

Abstract

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. In collaboration with investigators at the CDC/NCHS, we developed and implemented an allergy/asthma focused component for the National Health and Nutrition Examination Survey (NHANES). This component, included in NHANES 2005-2006, queried on allergy and asthma prevalence and morbidity, measured levels of common indoor allergens and endotoxin in bedroom dust, and quantified total and allergen-specific IgE levels in serum of more than 9000 participants. 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 individuals with asthma who were sensitized and exposed to dog or/and cat allergens had more asthma attacks and emergency care visits for asthma. Our results suggest that among pet-sensitive asthmatics, more than 1,700,000 excess asthma attacks and nearly 700,000 excess emergency care visits for asthma each year are associated with exposure to elevated levels of pet allergens in the bedroom. The findings highlight the importance of implementing environmental allergen control in homes of asthmatics who are sensitized to dog or/and cat allergens and have these pets at home. Using data from NHANES, we determined whether sensitization to common food allergens increased in U.S. children from 1988-1994 to 2005-2006 and whether these trends differed by race and/or ethnicity. In contrast with a body of literature showing increased prevalence of self-reported food allergy and increased health care utilization for its manifestations, NHANES data (NHANES III, NHANES 2005-2006) suggested that sensitization to milk, peanut, and egg, as measured by food-specific IgE, remained constant, while sensitization to shrimp decreased among children aged 6-19 years. On the other hand, we observed a trend toward increased prevalence of moderate- and high-level sensitization to the combination of milk, egg, and peanut among non-Hispanic blacks but not among other racial/ethnic groups. To further elucidate the role of sociodemographic characteristics in food allergy, we examined whether there were racial/ethnic and/or socioeconomic differences in the association between sensitization to common foods and self-reported food allergy. This association was strongly dependent on race/ethnicity and socioeconomic status in NHANES III, suggesting under-recognition of food allergy among poorer and minority children, or alternatively, over-recognition among high-income and non-minority children in the early 1990s. Our results may reflect either changes in the relationship between sensitization and clinical allergy or changes in the recognition and diagnosis of food allergy. In collaboration with US and international experts with backgrounds in allergy and asthma, we critically reviewed trials and research relevant to the prevention or control of asthma through environmental intervention. Our working group reviewed socioeconomic and structural challenges to changing environmental exposure and offered recommendations for creative study design to overcome these challenges in trials to improve asthma management. We also discussed indoor exposure assessment methodologies and the biologic properties of allergens and indoor pollutants as they relate to the risk of asthma and asthma morbidity and the possible protective effects of some of those exposures. Our goal was not only to identify important limitations and gaps in scientific methodologies and knowledge, but also propose and prioritize areas for future research. The working group report, which summarizes recommendations of the group, will serve as guidance for future research in the study of the indoor environment and on environmental interventions as they pertain to the prevention and management of asthma and airway allergies. 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 establishes 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.