What is asthma?
Asthma is a common disease of the lungs characterized by intermittent episodes of shortness of breath, wheezing, cough, and feelings of chest tightness. As the prevalence of allergies has increased in the past 50 years, the prevalence of asthma has also increased, and asthma now affects approximately 7% of the population. There is significant geographic variation in the prevalence of asthma with the highest prevalence occurring in countries with a western lifestyle.
What causes asthma?
Asthma occurs in genetically susceptible people who encounter environmental stimuli (especially in young childhood) that promote asthma. Although asthma is frequently one manifestation of an allergic tendency in an individual, it is not known why only ~25% of people with nasal allergies develop asthma. It is also not known why asthma is severe in some patients but relatively mild in most.
The environmental stimuli important for the development of asthma include allergens, viruses, bacteria, cigarette smoke, and food, but much needs to be learned about the relative importance of these different stimuli and the time windows that are important for specific environmental exposures. Also, it is thought that obesity is an independent risk factor for the development of asthma.
Why do the airways (“bronchial tubes”) narrow in asthma?
There are three main reasons for narrowing of the airways in asthma:
- Inflammation, or swelling, of the lining of the airway
- Bronchoconstriction, which happens when the muscles that wraps around the airway tighten and squeezes the airway
- Mucus overproduction, which happens when the airway makes too much mucus and blocks part or all of the airway
Narrow airways cause the symptoms of asthma, which are wheezing, coughing, tightness of the chest, and shortness of breath.
How is asthma diagnosed?
Asthma is diagnosed based on a person’s history of symptoms and with tests that can be done in the clinic. These tests can include:
- Lung function tests: these tests are designed to reveal narrowing of the airways and reversibility of such narrowing with inhaled drugs that open up the airways. Common lug function tests in asthma are spirometry and measures of peak flow (can be done with a hand held device)
- Measures of allergy: Asthma is common in people with allergies to environmental allergens and allergen avoidance can help control asthma. Allergen tests include skin prick tests or blood tests (for allergy proteins or for specific kinds of white blood cells, especially eosinophils).
How is asthma treated?
Asthma is a disease for which treatment is effective in providing good symptom relief and freedom from attacks in most patients. Treatment includes asthma medications, allergen avoidance, and disease education. People with asthma usually work with a health care provider to make an asthma treatment plan. This can include:
- Trigger avoidance
- Peak flow monitoring
- An asthma action plan - what to do when symptoms or peak flow get worse
Asthma attacks are periods of uncontrolled asthma in which the patient experiences increased symptoms of shortness of breath, chest tightness, cough, and sputum. Asthma attacks can come on quickly following a specific exposure (e.g. cat dander exposure) or during exercise. Attacks can also come on more slowly (e.g. asthmatics who get a head cold often notice that their asthma gets worse over a day or two).
Asthma attacks can sometimes be controlled by taking more frequent inhalations of albuterol until the attack resolves. More severe attacks, however, require a visit to an urgent care clinic or to the emergency room. Asthma attacks need to be taken seriously because they can sometimes be severe and even life threatening. Clues to a severe attacks include severe symptoms, or symptoms that are not relieved by albuterol. In addition, a history or prior attacks requiring treatment in a emergency room or in an intensive care unit should alert a patient that their asthma attack may need to be treated at the hospital. Although death from acute asthma attacks is relatively uncommon, it does occur, and an important warning sign is a previous bad attack of asthma.
What can someone who was recently diagnosed with asthma expect for their future health?
There is currently no cure for asthma. Medications and treatment plans can help reduce symptoms. While asthma can be very severe for some people, most people can lead normal lives with proper treatment.