|New National Study Links Asthma to Allergies
Researchers at the National Institutes of Health (NIH) have found
that more than 50 percent of the current asthma cases in the country
can be attributed to allergies, with approximately 30 percent of
those cases attributed to cat allergy.
"It has long been debated whether people who develop asthma
have a genetic propensity to develop allergies, or atopy," said
Darryl C. Zeldin, M.D., a senior investigator at the National Institute
of Environmental Health Sciences (NIEHS). "This new research
shows that 56.3 percent of asthma cases are attributed to atopy." Atopy
is a condition that results from gene-environment interactions
and can be measured by a positive skin test to allergens (or allergy
causing substances in the environment).
The study, available online today in the Journal of Allergy
and Clinical Immunology, was conducted by researchers at
the National Institute of Environmental Health Sciences (NIEHS)
and the National Institute of Allergy and Infectious Diseases,
both parts of the NIH. The data come from the Third National
Health and Nutrition Examination Survey (NHANES III), a nationally
representative sample of the population of the United States.
"Sensitization to cat appears to be a strong risk factor
for asthma in this study," said Zeldin. Zeldin and his co-authors,
however, point out that some research shows that exposure to cats,
particularly early in life, may be a protective factor. "We
are not advocating parents get rid of pets, but if you suspect
that you or your child might have cat allergies or get asthmatic-like
symptoms, you should consult with a physician about the best course
of action for your family," added Zeldin.
The NIH researchers looked at skin test data for ten allergens.
A positive skin test reaction to cat allergens accounted for 29.3
percent of the asthma cases, followed by the fungus Alternaria at
21.1 percent and white oak at 20.9 percent. "Each of 10 allergen-specific
skin tests was strongly associated with asthma; however, after
adjustment by a variety of subject characteristics and all the
allergens, only skin tests to cat, Alternaria and white
oak were independently and positively associated with asthma," said
Peter Gergen, M.D., M.P.H, of NIAID's Division of Allergy, Immunology
and Transplantation, a co-author on the paper.
Other allergens tested include: Ragweed, dustmites, Russian thistle,
Bermuda grass, peanuts, perennial rye and german cockroach. Approximately
10,500 individuals participated in the skin testing. During these
tests, skin was exposed to allergy-causing substances (allergens)
and a positive test was determined by the size of the reaction
on the skin.
"This study tells us that allergy is a major factor in asthma," Gergen
said. "But this study also tells us is that there are many
people who get asthma who donít have allergies. We need to do more
research to understand what is causing the asthma that is not related
"This study confirms that the environment plays a major
role in the development of asthma," said Zeldin. "Given
the complexity of this disease it won't be easy, but if we can
prevent, block or reverse atopy, we could reduce a large proportion
of asthma cases."
The National Institute of Environmental Health Sciences (NIEHS),
a component of the National Institutes of Health, supports research
to understand the effects of the environment on human health. For
more information on environmental health topics, please visit our
website at http://www.niehs.nih.gov/.
NIAID is a component of the National Institutes of Health, an
agency of the U.S. Department of Health and Human Services. NIAID
supports basic and applied research to prevent, diagnose and treat
infectious diseases such as HIV/AIDS and other sexually transmitted
infections, influenza, tuberculosis, malaria and illness from potential
agents of bioterrorism. NIAID also supports research on transplantation
and immune-related illnesses, including autoimmune disorders, asthma
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov.
Reference: Arbes SJ, Gergen,PJ Vaughn B, Zeldin
DC. Asthma cases attributable to atopy: Results from the Third National
Health and Nutrition Examination Survey. Journal of Allergy and
Clinical Immunology. September, 2007.