Allergies, Asthma and Exposures in the Homes of the U.S. Population
A Project for IMSM 2014
Agustin Calatroni and Herman Mitchell
Rho, Inc.
Chapel Hill, NC
Among the most inexplicable phenomena in the health of U.S. citizens has been the dramatic
increase in asthma and allergy. Asthma prevalence has increased 171% between 1980 and
2010. Increases in allergy have been equally surprising and 45% of the U.S. population is now
allergen to at least one allergen such as, cat, dog, cockroach, trees, grasses, foods, etc. In less
than 15 years, food allergies alone have increased 50% and now one in every 13 children has
an allergy to food.
The Centers for Disease Control and Prevention (CDC) has the responsibility for producing vital
and health statistics for the Nation which are used to determine health policy and programs, as
well as providing data to help researchers understand the nature and causes of disease. One
of the primary methods for accomplishing this goal is through the National Health and Nutrition
Examination Survey (NHANES) which is a program of studies designed to assess the health
and nutritional status of adults and children in the United States. This survey is unique in that it
combines interviews and physical examinations. The NHANES interview includes demographic,
socioeconomic, dietary, and health-related questions. The examination component consists of
medical, dental, and physiological measurements, as well as laboratory tests administered by
highly trained medical personnel.
For the first time in the history of these assessments, NHANES has collected extensive
information on both allergies as well as the potential allergen exposures in U.S. homes.
Although it is not fully understood why some people develop allergies and asthma while others
do not, it is generally accepted that asthma is the result of the interaction between genetic
susceptibility and environmental exposures. Among the environmental exposures that are
believed to play a role in asthma are exposures to indoor allergens, such as dust mite,
cockroach, dog, cat, and fungal allergens. In addition, exposure to bacterial endotoxins,
compounds found in the outer membrane of a common class of bacteria, also may play a role in
the allergic response. These common home exposures not only play a role in developing
allergies, but for those with asthma, these allergen can trigger asthma attacks leading to
emergency department visits, hospitalization or even death.
Asthma is the most common chronic disease among children, the number one reason they miss
school and the major reason for emergency department visits (with the exception of injuries and
accidents). The direct and indirect costs associated with asthma and asthma exacerbations
exceed $60 billion dollars a year. Since we spend 90% of our time indoors, these home
exposures are critically important to understanding the development of allergies and asthma as
well as understanding their role as trigger for asthma attacks.
Rho, in collaboration with NIH’s National Institute of Environmental Health Sciences and the
CDC has been preparing analyses and publications on this unique dataset. While the CDC
took great care and devoted millions of dollars to collect this representative sample of
approximately 8,000 families, there remain complications with these data that can be addressed
through creative statistical and mathematical modelling. First, we would like to use the wealth
of questionnaire data from these NHANES surveys (housing, demographics, health outcomes,
etc.) and laboratory data such as the participant’s sensitization level, etc. to establish prediction
models regarding home exposures. If this can be accomplished, the extraordinary expense and
difficulty of home visits, dust sample collections, and laboratory assays could be minimized.
Also, these models could facilitate clinical guidance for families with allergies and asthma and
serve as the basis for reducing asthma exacerbations.
Typically, NHANES datasets have very few missing data, however due to the very complicated
laboratory assays there are a substantial amount of missing data for the allergen datasets. The
second goal of this project is to build upon the prediction models described above to develop
imputation models for the missing exposures data in this national sample.
References
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Guide to Community Preventive Services. Asthma control: Home-based multi-trigger, multicomponent
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http://www.cdc.gov/nchs/data/nhanes/nhanes_05_06/overviewbrochure_0506.pdf
http://www.cdc.gov/nchs/data/nhanes/nhanes_05_06/allergen_manual_06.pdf
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