- What Is Asthma?
- What Causes Asthma?
- Who Gets Asthma?
- Why Is Asthma Increasing?
- How Is Asthma Diagnosed?
- How Is Asthma Treated?
Asthma is a chronic disease that includes bronchoconstriction (tightening of the muscles around the airways) and inflammation (swelling) of the bronchial tubes. During normal breathing, air flows freely in and out of the lungs. But, during an asthma episode, the lining of the airways swell, muscles around the airways tighten and mucus clogs the tiny airways in the lungs, making breathing difficult. The airways become overly responsive to environmental changes, sometimes resulting in wheezing, coughing, breathlessness, or tightness in the chest.
Asthma symptoms vary from hour-to-hour, day-to-day, week-to-week and over months. They are often worse at night and in the early hours of the morning. The severity of asthma varies from individual to individual. Some patients have occasional symptoms (for example after strenuous exercise), others have symptoms that may interfere with daily life.
People with asthma have airways that narrow more easily than people who do not have asthma and may be allergic or sensitive to inhaled irritants. The causes of the airway abnormality and its relationship to being allergic are not known. A variety of factors can set off an asthma episode including viral infections; exposure to allergens (e.g. dust mites, (dander) protein particles shed by cats and dogs and pollen); exercise; tobacco smoke; air pollution; strong emotional expressions; chemical irritants; and drugs (aspirin and beta blockers). Each person with asthma reacts to a different set of factors. Identification of these factors in an individual is a major step towards learning how to prevent an asthma episode.
The World Health Organization estimates that between 100 and 150 million people around the globe suffer from asthma and this number is rising. World wide, deaths from this condition have reached over 180,000 annually. Asthma is a public health problem for both developed and developing countries. It occurs in all age groups and all ethnic groups. However, it often starts in childhood. Indeed, asthma is the single most common chronic disease causing absence from school.
The rapid rise of asthma around the world is one of the biggest mysteries in modern medicine. The most striking increases have occurred in Australia where about one-quarter of children are diagnosed with asthma. In the United States, the number of people with asthma has more than doubled to an estimated 17.3 million in 1998 from 6.7 million in 1980.
Research on this problem has focused on environmental allergens and viral infections in infants and young children. Ten years ago, scientists thought that diesel exhaust and other pollutants might be causing the asthma epidemic. However, they now believe that the picture is more complex. In addition to studies to examine the role of genetic factors in the development of asthma, researchers are looking at the immune system in early life.
A careful medical history, physical examination and tests of pulmonary function provide information needed for a diagnosis of asthma. Symptoms may include breathlessness, wheezing, chest tightness and cough, worse particularly at night or in the early hours of the morning. Symptoms occur or worsen in the presence of exercise, allergens, irritants and viral infections. Young children whose primary symptom is a cough or who wheeze with respiratory infections are often misdiagnosed as having bronchitis or pneumonia (including acute respiratory infection, ARI) and thus are ineffectively treated with antibiotics or cough suppressants. Tobacco smokers and elderly patients frequently suffer from chronic obstructive pulmonary disease with symptoms similar to asthma. Yet they may also have asthma and benefit from treatment.
Measures of lung function are useful both for diagnosis and to monitor the course of asthma. Such tests include spirometry to provide an assessment of airflow limitation and peak flow to measure the maximum speed at which air can flow out of the lungs. Spirometry is performed in the clinician's office. Peak flow meters are portable, plastic and ideal for use in home and work settings and thus provide most patients and their health care provider with an effective method to evaluate response to therapy and detect early signs of a developing asthma episode.
Control of asthma is defined as the absence of symptoms and acute episodes, no use of relief medication, no emergency room visits, normal activity level, including exercise and normal lung function. Control of asthma can be achieved through the implementation of an effective asthma management program. An effective management program includes the following:
- Educate patients to develop a partnership in asthma management
- Assess and monitor severity by measuring lung function and tracking symptoms.
- Avoid or control factors that cause asthma
- Establish medication plans for long-term management
- Establish plans for managing asthma episodes
- Provide regular follow-up care
Two types of medications are used:
- Long term controller medications such as anti-inflammatory agents (inhaled corticosteroids) or leukotriene receptor antagonists can help keep symptoms and episodes from starting.
- Quick relief medications (short-acting bronchodilators) work fast to treat episodes before they occur (as with exercise induced asthma) or relieve symptoms as they happen.
Modified from the World Health Organization fact sheet 206, December 1998