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. The new 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 medical conditions. For example, we investigated whether elevated albuminuria, which is not only a marker of renal impairment but also a marker of endothelial dysfunction, is an early predictor of mortality from chronic lower respiratory disease and influenza and pneumonia. Our analysis included a large sample of NHANES III participants (N=7,944) who were followed for mortality until 2015. Our results showed that a 10-fold increase in albuminuria was associated with an 88% higher mortality risk from chronic lower respiratory disease and with a 103% increase in mortality risk from influenza and pneumonia. The findings from this nationally representative study suggest that elevated albuminuria is associated with subsequent mortality from chronic lower respiratory disease and from influenza and pneumonia, independent of diabetes or chronic kidney disease. Our study, with an extensive follow-up time of up to 27 years, is one of the few studies that have investigated albuminuria and long-term mortality from influenza/pneumonia and chronic lower respiratory disease. In collaboration with several federal agencies and national asthma experts, we have developed and implemented a supplemental questionnaire for the National Ambulatory Medical Care Survey (NAMCS) that provides comprehensive information about the provision and use of office- and community health center (CHC)-based medical care services. The supplemental questionnaire in the NAMCS 2012 was designed to assess clinician agreement, self-efficacy and self-reported adherence with the asthma guidelines at the national level. Findings from this study demonstrated notable differences in guideline agreement, adherence, and implementation among asthma care clinicians. While specialists had higher adherence rates, little was known about whether guideline use differed between allergists and pulmonologists. We showed that agreement and self-efficacy to implement guidelines did not differ between the specialist groups. However, compared to pulmonologists, allergists were more likely to perform spirometry, ask about nighttime awakening and emergency department or urgent care visits, assess home triggers and perform allergy testing. These differences in guideline adherence between the groups were mostly explained by differences in practice-specific characteristics such as patient population. Recommendations with low implementation, including assessment of inhaler technique, offer opportunities for further exploration and could serve as targets for increasing guideline uptake. Improving understanding of factors and clinical decision-making underlying variations in guideline adherence and group-specific differences is important and could better inform guideline recommendations and a personalized approach to asthma care. 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.