Causes of Adult Asthma

Causes

Asthma has dramatically risen worldwide over the past decades, particularly in developed countries, and experts are puzzled over the cause of this increase. The mechanisms that cause asthma are complex and vary among population groups and even from individual to individual. Many asthma sufferers have allergies, and some researchers are targeting common factors in both these conditions. Not all people with allergies have asthma, however, and not all cases of asthma can be explained by allergic response.

Asthma is most likely to be caused by a convergence of factors that can include genes (probably several) and various environmental and biologic triggers (e.g., infections, dietary patterns, hormonal changes in women, and allergens).

The Allergic Response

Nearly half of adults with asthma have an allergy-related condition, which, in most cases developed first in childhood. (In patients who first develop asthma during adulthood, the allergic response usually does not play a strong causal role.) Important irritants or allergens include:

• Dust mites, specifically mite feces, which are coated with enzymes that contain a powerful allergen. These are the primary allergens in the home.
• Animal dander.
• Pollen. An asthma attack from an allergic response to pollen is more likely to occur during extreme air changes, such as thunderstorms. Major weather changes, such as El Nino, can affect the timing of allergy seasons. For example, in 1998, when the effects of El Nino were very strong, allergy and asthma attacks were markedly increased, and maximum tree pollen counts occurred 2 to 4 weeks earlier and mold counts 2 to 3 months earlier than in the previous year.
• Molds. A 2002 study suggested that molds might produce a worse asthma attack in adults than other allergens.
• Fungi.
• Cockroaches. Cockroaches are major asthma triggers and may reduce lung function even in people without a history of asthma.
• Fossil Fuels. Certain chemicals may trigger allergic rhinitis. Some experts believe that refined fossil fuels, such as diesel fuel and particularly kerosene, may be important triggers for allergic rhinitis. And, in people who already have allergies or asthma, exposure to such fossil fuels may worsen symptoms.