Are asthma cases on the rise?

Asthma is a chronic lung disease characterized by episodes of airflow obstruction known as asthma attacks.  During an asthma attack, small muscles surrounding the airways contract, resisting the flow of air into and out of the lungs. Inflammation and swelling of the airways is also a consistent feature among asthmatics.  Asthma attacks can be triggered by a number of factors including cold air, exercise, infection, allergens, occupational exposures, and airborne irritants such as tobacco smoke. Symptoms of asthma include wheezing, coughing, shortness of breath, and chest tightness.

Statistics indicate that the number of people with asthma in the U.S.  appears to be on the rise. According to the Centers for Disease Control and Prevention (CDC), about one in 12, or about 25 million people in this country has asthma.  This number is up from around 20 million people with asthma as recently as 2001.  Of those diagnosed with asthma, the greatest rise in asthma rates affects African American children.

Two questions pertaining to asthma have puzzled medical researchers over the past couple of decades: 1) what causes asthma to develop in the first place and 2) what is responsible for the increasing incidence of people with asthma?

What causes asthma? The answer to this question remains unanswered.  Doctors know the "triggers" for asthma attacks, such as cold air, exercise, cigarette smoke, etc., but the reasons that asthma develops in people is still being researched. Fortunately, even though there is no cure for asthma, treatment is available to manage the disease and in many cases, prevent its symptoms.

Why is asthma on the rise? Although a definite explanation has not yet been found, several theories for the increased incidence of asthma have been developed.

1. A leading theory is known as the 'hygiene hypothesis'.  This theory suggests that living conditions in this country might be so clean that children are not being exposed to germs that teach their immune systems to tell the difference between harmless and harmful irritants. Although not universally accepted by the medical community, this concept is supported by studies that show that children living around animals on farms or attending daycare develop fewer allergic diseases.
    
2. The rise in asthma cases may also be due to an increase in environmental allergens and irritants. These include airborne pollens which appear to be increasing due to global climate change and “urban pollution” such as ozone and particulate matter from industry and car traffic.
    
3. Some studies have found evidence suggesting that obesity predisposes to the development of asthma.  It is not clear, however, whether this is related to body weight alone, or perhaps due to a less active lifestyle which could affect lung strength and function.
    
4. Some research indicates that increased use of certain medications, particularly antibiotics, contributes to the increase in asthma. Researchers suggest that early antibiotic use changes the bacterial flora, which impacts the development of allergic diseases such as asthma.

While the underlying causes for asthma and reasons for the increasing percentage of Americans with asthma are still under investigation, the Centers for Disease Control (CDC) are doing the following to help reduce the burden of this disease:

• Instituting measures to improve indoor air quality for people with asthma through smoke-free laws and policies.
   
• Teaching patients how to avoid asthma triggers, such as tobacco smoke, mold, pet dander, and outdoor air pollution.
   
• Encouraging doctors to prescribe inhaled corticosteroids for all patients with persistent asthma, and to use a written asthma "action plan" to teach patients how best to manage their symptoms.
   
• Promoting measures that prevent asthma attacks, such as increasing access to corticosteroids and other prescribed medicines.
   
• Encouraging home environmental assessments and educational sessions conducted by doctors, health educators, and other health professionals.