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Asthma Information Book
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astma, asma
Asthma Information & Explanation
In many people, asthma appears to be an allergic reaction to substances commonly
breathed in through the air, such as animal dander, pollen, or dust mite
and cockroach waste products. The catch-all name for these substances,
allergens, refers to anything that provokes an allergic reaction. Some
people have a genetic predisposition to react to certain
allergens.
When these people breathe in the allergen, the immune
system goes into high gear as if fighting off a harmful parasite. The
system produces a molecule called immunoglobulin E (IgE), one of a class
of defensive molecules termed antibodies. The IgE antibody is central to
the allergic reaction. For example, it causes mast cells, a type of
specialized defensive cell, to release chemical "weapons" into the
airways. The airways then become inflamed and constricted, leading to
coughing, wheezing, and difficulty breathing -- an asthma attack.
Without treatment, such as inhaled corticosteriods to reduce the
inflammation, asthma attacks can be deadly. The overall death rate for
asthma, however, is low.
Why is Asthma on the
Rise?Although several theories exist about why
asthma rates have risen during the last two decades, there probably is no
simple answer, says Calman Prussin, M.D., head of the clinical
allergy and immunology unit at NIAID.
One theory is that people
today, especially in developed countries, are spending more time indoors,
Dr. Prussin says. We are therefore exposed to more indoor allergens, such
as dust mite allergen, that cause asthma. "Our houses are now hermetically
sealed to save heating and cooling energy," he notes, "and unfortunately
this causes more indoor allergen exposure."
Another reason may be
that people today live in cleaner, more sanitary conditions than they did
before the industrial revolution, relatively free of disease-causing
viruses and bacteria, he says. This clean living affects our immune
system. The immune system's defensive white blood cells, called T cells,
have two basic "settings," he explains. Th1 cells fight infectious viruses
and bacteria. Th2 cells fight parasites but are also involved in allergic
reactions.
"We are exposed to fewer viruses and bacteria than
people were 100 years ago, so perhaps our immune systems have not learned
to make Th1 cells as well," Dr. Prussin says. "That means we have a
greater proportion of Th2 cells in our bodies, which might lead to more
allergies and asthma."
Other theories point to increased levels of
air pollutants, a decline in the amount of exercise people get, or rising
obesity as factors in the increase of asthma.
Asthma Information & Statistics
- In 1998, an estimated 17 million Americans, or 6.4 percent of the
population, had asthma. Children account for 4.8 million of Americans
with asthma.
- Asthma affects slightly more African Americans (5.8 percent) than
whites (5.1 percent). In 1993 however, African Americans were 3 to 4
times more likely than whites to be hospitalized for asthma. In 1996,
African Americans were 4 to 6 times more likely than whites to die from
asthma.
- More than 5,000 people die from asthma each year in the United
States. Although asthma deaths are infrequent, they have increased
significantly during the last two decades. From 1975-1979, the death
rate was 8.2 per 100,000 people. That rate jumped in 1993-1995 to 17.9
per 100,000.
- In 1994, asthma caused 451,000 hospitalizations. Children under 15
accounted for 169,000 of these.
- In 1995, asthma caused more than 1.8 million emergency room
visits.
- Asthma cost the U.S. economy an estimated $10.7 billion in 1994,
including a direct health care cost of $6.1 billion and indirect costs,
such as lost work days, of $4.6 billion.
Keeping on Top of Your Condition
Keeping in tune with your disease or condition not only makes treatment less intimidating but also increases its chance of success, and has been shown to lower a patients risk of complications. As well, as an informed patient, you are better able to discuss your condition and treatment options with your physician.
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References
- Centers for Disease Control and Prevention (CDC), Morbidity
and Mortality Weekly Report 47(47):1022-25 (December 4, 1998).
- C. Cannon et al. American Journal of Respiratory and
Critical Care Medicine 158 (1): 320-34 (1998).
- CDC Surveillance Summaries, April 24, 1998, from Morbidity
and Mortality Weekly Report 47(SS-1): 1-28 (1998).
- CDC, Morbidity and Mortality Weekly Report 45(17): 350-3
(1996).
- K.B. Weiss et al. Journal
of the American Medical Association 264(13):1683-7 (1990).
- CDC, National Center for Health Statistics, National Vital
Statistics Report 47(4) (1997).
- CDC Surveillance Summaries, April 24, 1998, from Morbidity
and Mortality Weekly Report 47(SS-1): 1-28 (1998).
- National Center for Health Statistics, National
Health Interview Survey, 1994.
- CDC Surveillance Summaries, April 24, 1998, from Morbidity
and Mortality Weekly Report 47(SS-1): 1-28 (1998).
- K.B. Weiss et al. Journal
of Allergy and Clinical Immunology 106(3): 493-99 (2000).
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