Most of us breathe without even thinking about it. In and out, in and out, the air moves easily and effortlessly. But there are millions of people for whom breathing can never be taken for granted, and their numbers are increasing: asthmatics.
Asthma is a narrowing of airways in the lungs that causes coughing, wheezing and gasping. It’s probably been around forever, but recent years have seen a marked increase in its incidence world-wide, and nobody is exactly sure why. We know more about the disease than we ever have before, we have new methods of fighting it, and paradoxically, more people are afflicted than ever before.
How many people? Figures aren’t available for all countries, and asthma is notoriously under-reported (because many people who have occasional problems breathing don’t ever see a doctor), but the best guess is staggering: worldwide, it’s believed that 150 million people–five times the population of Canada–are afflicted. In some countries, more than one-third of all children suffer from the disease. Right here in North America, more than 10 percent of children are afflicted. And round the world, the number of cases has doubled, tripled or even quadrupled in the last two or three decades.
What’s frightening about asthma is that it interferes with the vital process of breathing. Our lungs contain 300 million tiny air sacs. Blood flowing around these sacks receives oxygen from the outside world and unloads carbon dioxide and other waste gases for exhalation.
An asthma attack starts with some kind of inflammation. It can be brought on by any one of a number of triggers. One of the most common is an allergen of some kind. The body’s immune system responds to substances we’re allergic to by producing an antibody called IgE, which in turn causes mast cells (which are found in the lining of our nasal passages, lungs and intestines) to produce histamine. This hormone makes our blood vessels expand and the smooth muscle around our airways to contract. It’s the same hormone that stuffs up our noses when we have a cold.
In asthmatics, however, the lungs over-react to the stimulus provided by IgE. Histamine floods the lungs, and any or all of three processes that can reduce the size of the breathing passages takes place: the passage lining swells, more mucus is secreted, and muscles around the airway tighten. This makes breathing, particularly exhaling, difficult. Wheezing and whistling sounds may result in severe attacks, and the asthmatic feels like he or she is underwater and trying to breath through a drinking straw to the surface.
Common allergens that trigger asthma attacks include such unpleasant substances as cockroach parts and dust-mite feces, which is one reason asthma is particularly prevalent among poor people living in pest-ridden inner-city housing. (Cockroach parts are particularly potent in triggering asthma among those allergic to them, according to a recent study.) Pollen, animal dander and certain foods can also set off attacks…but then again, they may not. One of the frustrating things about the disease for sufferers is that what sets of an attack one time may not the next time, whereas something that has never brought on an attack before may suddenly do so.
Besides allergies, triggers include colds (colds bring on many asthma attacks among children); chemical irritants such as strong perfumes and household cleansers; tobacco smoke, both your own and second-hand; gastroesophageal reflux, a “burping up” of acid stomach contents; various drugs and foods, such as aspirin and sulfites; exercise (an estimated 85 percent of asthmatics wheeze after exercise, especially after running or cycling; swimming seems to be much more benign an exercise); stress and fatigue, and even violence (a study suggests children exposed to real-life violence are twice as likely as other children to suffer serious attacks).
Severe air pollution can bring on attacks, but increasing outdoor air pollution doesn’t seem to be behind the increase in asthma cases; some of the places with the highest incidences of asthma have very clean air, and in North America, at least, air pollution in most cities hasn’t gotten any worse in 10 years. Many scientists are pointing to indoor air pollution as a possible cause instead. Our modern houses and office buildings are sealed boxes with central heating and air-conditioning, double-glazed windows and wall-to-wall carpeting. In some of them, the windows don’t even open. Not only do the carpets provide a good home for dust mites and mould, but the closed environment concentrates the volatile organic compounds emitted by synthetic carpet and vinyl upholstery.
There is no cure for asthma, but it can be controlled, and better therapies are being developed all the time. The first step in controlling asthma is to stay away from possible triggers, but that’s difficult. As noted earlier, it’s hard to be sure exactly what triggered and attack, and it could be something so ubiquitious that it’s almost impossible to avoid (i.e., the common cold).
Bronchodialators, drugs that open the airways and provide fast, short-acting relief, are commonly used by asthmatics, who spray them into their lungs with hand-held inhalers. Longer-term relief can be obtained with synthetic hormones called corticosteroids (not to be confused with the anabolic steroids that got Ben Johnson into such trouble). These drugs, which can be inhaled, swallowed or injected, reduce the inflamation of the airways. Studies show that heavy and steady use of corticosteroids soon after asthma is diagnosed may help increase lung capacity in the long term and that patients with moderate to severe asthma who take them have half as many hospitalizations for asthma as other patients.
These two methods of controlling asthma have been around for 20 years, but now there are exciting new drugs on the horizon called leukotriene modifiers. Leukotrienes are one of the substances that flood the body during the inflammation portion of asthma, so inhibiting their production could reduce inflammation and either prevent the onset or lessen the severity of an attack. Two drug companies are also looking at antibodies designed to neutralize a substance called interleukin-5, which tells eosinophils–cells that play a major role in inflammation–to fire up. If the antibodies work, those cells would never get the message that there was an allergen to react to, and would stay calm.
Finally, scientists believe there is hope for an asthma vaccine, based on Japanese finding that a tuberculosis vaccine given to children in their first year lessened the chance of their developing asthma later on. The vaccine apparently stimulates a part of the immune system that babies born of parents with allergies have a deficiency in, which gives credence to the notion that asthma is, at least in part, an inherited disease.
In fact, researchers believe it is only a matter of time before babies who are susceptible to asthma will be identified at birth, and then given a vaccine or other treatment to lessen their risk of developing the disease later.
If that happens, maybe the rising tide of asthma will be driven back, and millions of people will breathe a sigh of relief–easily.
