Asthma
According to the most recent study of
asthma prevalence conducted by the Centers
for Disease Control and Prevention, in
2001, 31.3 million people (114 people per
1,000 - U.S.) had ever been diagnosed with
asthma during their lifetime. Beginning
with the 2001 National Health Interview
Survey (NHIS), current asthma prevalence
includes people who have been diagnosed
with asthma by a health professional and
who still have asthma. In 2001, 73 people
per 1,000 or 20.3 million people, had
asthma at the time of the interview. Rates
decreased with age; 87 per 1,000 children
0-17 years (6.3 million children) had
asthma compared to 69 per 1,000 adults 18
years and over (14 million adults).
When race/ethnicity is considered,
current asthma prevalence was about 10%
higher among non-Hispanic blacks compared
to non-Hispanic whites and about 40%
higher compared to Hispanics. Females had
a 30% higher prevalence compared to males.
However, this pattern was reversed among
children. The current asthma prevalence
rate for boys aged 0-17 years (99 per
1,000) was over 30% higher than the rate
among girls (74 per 1,000).
Asthma is a disease that causes the
airway tubes that carry air-in the lungs
to overreact and become "twitchy" so they
become temporarily constricted or blocked
in response to an asthma trigger. When
this occurs, the person with asthma may
feel as though he or she cannot get enough
air or simply can't breathe effectively.
Put in more technical terms, asthma is
characterized by airway inflammation,
increased airway responsiveness
("twitchiness"), and variable airflow
obstruction. Most researchers agree that
the tendency to have asthma is inherited
and that the airways tendency to overreact
is often present from infancy.
One of the defining characteristics of
asthma is that the airway obstruction is
reversible (though not always completely
reversible) and may resolve on its own or
with treatment. Since the airway
obstruction is variable, asthma may be
described as "episodic" in that most
people who have it breathe normally or
near normally between episodes or acute
attacks. In addition to being episodic,
asthma is also considered to be chronic
(an ongoing problem) and people with
asthma have airways that remain inflamed
and may get constricted after exposure to
an asthma trigger.
During an asthma attack, the
bronchioles and alveoli (conducting
airways of the lungs) become narrowed or
blocked. The muscles that encircle these
bronchioles and alveoli that conduct air
within the lungs constrict (tighten). When
the airways narrow, fluid, blood cells,
and irritating chemicals produced by the
body enter the bronchioles and cause the
linings of the airways to become inflamed.
This inflammation further narrows the air
passages. The inflammation signals mucous
glands in the bronchioles to secrete more
mucus than usual, which causes the airways
to become plugged or blocked.
Types of Asthma
Although asthma is characterized by
specific changes in the lungs that result
in respiratory difficulty for asthma
sufferers, it has also been categorized in
a variety of ways. It should be noted that
some of the conditions listed below have
similar components to those of Chronic
Obstructive Pulmonary Disease (COPD) and
Interstitial Lung Disease (ILD). This
means that some have an inflammatory
component.
- Extrinsic asthma is asthma that is brought on by external agents such as pollens or chemicals. It is commonly diagnosed early in life, and is usually caused by the body's responses to inhaled allergens.
- Intrinsic asthma is asthma due to within-the-body (endogenous) factors such as adrenalin release due to stress or to exertion. It generally develops later in life, and very little is known about what causes it. Intrinsic asthma tends to be less responsive to treatment than extrinsic asthma. Triggering factors include infection, exercise, and drugs such as aspirin.
- Exercise-induced asthma is defined as asthma attacks that follow a period of exercise. Such attacks are usually short-lived and resolve without treatment. People with exercise-induced asthma may also have other underlying precipitating factors.
- Acute severe asthma, previously known as status asthmaticus, is a sudden, intense, and continuous aggravation of asthma that does not respond to the usual therapeutic measures. It is characterized by breathing difficulty that leads to exhaustion and collapse. People with acute severe asthma can deteriorate very rapidly and can die within the first 24 hours of onset.
- Occupational asthma, which usually occurs in response to irritants and allergens in the workplace. Those with occupational asthma may not experience symptoms when not at work.
- Weather-related asthma occurs in response to changes in weather.
- Asthma may be triggered by gastro esophageal reflux disease (GERD).
- Acute or chronic sinusitis and allergic rhinitis may aggravate asthma.
- Sleep or nocturnal asthma is asthmatic symptoms that become more evident at night. These symptoms are probably not related to lying down or to sleep and instead probably reflect the ongoing inflammatory state of the airways.
- Hormone-related asthma may occur in some women who experience aggravation of asthma shortly before their menstrual periods.
- Use of oral contraceptives may also aggravate asthma. An overactive thyroid gland has been linked to provoking or worsening asthma; treatment of the overactive thyroid may help relieve asthma symptoms.
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