Indoor Allergens And Asthma

National Institute Of Environmental Health Sciences

Investigators

Linked publications & trials

Abstract

Our research program focuses on the role of the environment in the development and exacerbation of asthma and allergic diseases. 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 has allowed 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. This component 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. It established a second point-in-time estimate for evaluating allergen and endotoxin exposure trends in U.S. homes, the 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. The data have enabled more robust and generalizable investigations of the role of allergen/endotoxin exposures and IgE-mediated sensitization in allergic diseases than previously possible. We have made significant advances in our understanding of the prevalence and determinants of indoor allergen/endotoxin exposures, and their relationships with allergic disease. Our research has demonstrated that exposure to indoor allergens and endotoxin is common but highly variable in U.S. homes. Our findings highlight the impacts and importance of environmental factors in human health and disease, including asthma. Although our focus continues to be on asthma/allergy-related outcomes, we have extended interest into other respiratory outcomes. For example, we examined whether levels of serum antioxidant vitamins A, C, D and E were associated with respiratory morbidity and mortality among adults in the United States. Despite the increasing interest in studying the role of serum antioxidant vitamins in respiratory health, only few large-scale studies, all of which have been conducted in Europe, have investigated serum antioxidant vitamin levels in relation to respiratory mortality at the national level. Our comprehensive, nationally representative, pooled analysis of data from NHANES is the largest investigation to date including data from over 34,000 participants. This analysis, with an extensive follow-up time of up to 27 years, showed that among U.S. adults, lower levels of serum antioxidant vitamins A, C, D and the alpha-tocopherol form of vitamin E were associated with higher respiratory morbidity and mortality, while the gamma-tocopherol form of vitamin E showed opposing effects. Lower serum levels of vitamins C and alpha-tocopherol were associated with wheeze and chronic bronchitis/emphysema, albeit the effects of alpha-tocopherol were primarily seen in smokers. Lower levels of serum vitamin A, C, and D were associated with increased mortality from chronic lower respiratory disease and influenza/pneumonia. Our findings underscore the importance of antioxidant vitamins in respiratory health, suggesting that serum levels of antioxidant vitamins could be useful in identifying individuals who might be at higher risk for respiratory morbidity and mortality. We continue to study the complex relationships between allergen exposures, allergic sensitization, and disease in more detail, as the NHANES data allow for the investigation of many interesting relationships. Our research will lead to a better understanding of the characteristics of environmental exposures, such as indoor allergen and endotoxin exposures, and their role in allergic disorders, which in turn provides insights into development of effective environmental intervention approaches for the management of allergic diseases such as asthma.