What puts you at risk
Asthma can develop at any stage in life, but medical scientists have no simple answers to explain why women suddenly develop the condition as adults. They do know that it's not a disease caused by a single factor. Asthma is a complex disease -- or group of diseases, say some experts -- that can result from multiple factors, usually involving an interaction between genes and the environment. More than 60 per cent of people who develop asthma have a genetic allergic predisposition.
Allergens such as pet dander, house dust mites, pollen, moulds or latex can trigger asthma. Adults without allergies can develop asthma by being around chemical irritants and more than 300 chemicals one can be exposed to in the workplace. Other risk factors include respiratory infections, smog, obesity and hormonal fluctuations in women. Certain medications, including acetylsalicyclic acid and beta-blockers, also trigger asthma in some people.
Why is asthma increasing at epidemic rates in both children and adults?
Asthma rates are eight to 10 times higher in urban industrialized nations like Canada than in developing countries. Although researchers have yet to pinpoint the cause, they do have some persuasive theories.
The hygiene hypothesis proposes that due to our obsession with cleanliness and overuse of antibiotics, young children don't get enough exposure to bacteria, so their immune systems overreact to allergens. Poor air quality also may be a factor. Outdoor pollutants as well as allergens and chemicals in carpets and cleaning products trapped inside well-sealed homes may interact with overactive immune systems to induce asthma.
Why is the disease more common and often more severe in women than men?
"We're just beginning to understand this," says Day. "Women have smaller airways, which are also smaller in proportion to their lung size." Hormonal fluctuations may be a factor, too. Women's airways may become slightly narrower just before their period begins, and studies have found that some women have more severe asthma symptoms then.
If you think you might have asthma, get tested. To diagnose asthma, your doctor should do a chest examination, take a careful medical and family history and perform a lung function test.
A spirometry test measures your breathing and determines how narrow the airways in your lungs are. If your airflow readings are below normal and an asthma drug improves your breathing, this confirms the diagnosis. Some people will have a normal spirometry test result and be asked to take a metacholine challenge test. You may have asthma if your airflow readings drop significantly after receiving a very low dose of this agent.
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