Asthma

Asthma is a disease of the human respiratory system in which the airways narrow, often in response to a "trigger" such as exposure to an allergen, cold air, exercise, or emotional stress. This narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing, which are the hallmarks of asthma. Between episodes, most patients feel fine.

Epidemiology

Asthma is usually diagnosed in childhood. The risk factors for asthma include:

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• a personal or family history of asthma or atopy;
• triggers (see Pathophysiology above);
• premature birth or low birth weight;
• viral respiratory infection in early childhood;
• maternal smoking;
• being male, for asthma in prepubertal children; and
• being female, for persistence of asthma into adulthood.

There is a reduced occurrence of asthma in people who were breast-fed as babies. Current research suggests that the prevalence of childhood asthma has been increasing. According to the Centers for Disease Control and Prevention's National Health Interview Surveys, some 9% of US children below 18 years of age had asthma in 2001, compared with just 3.6% in 1980 (see figure). The World Health Organization (WHO) reports{{an|WHO}} that some 8% of the Swiss population suffers from asthma today, compared with just 2% some 25–30 years ago. Although asthma is more common in affluent countries, it is by no means a problem restricted to the affluent; the WHO estimate that there are between 15 and 20 million asthmatics in India. In the U.S., urban residents and Hispanics and African Americans are affected more than the population as a whole. Globally, asthma is responsible for around 180,000 deaths annually.{{an num|WHO|25}}

Related Topics:
Prevalence - Centers for Disease Control and Prevention - World Health Organization

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Asthma and athletics

Asthma appears to be more prevalent in athletes than in the general population. One survey of participants in the 1996 Summer Olympic Games showed that 15% had been diagnosed with asthma, and that 10% were on asthma medication.{{an|Olympics}} There appears to be a relatively high incidence of asthma in sports such as cycling, mountain biking, and long-distance running, and a relatively low incidence in weight lifting and divers. It is unclear how much of these disparities are because of the effects of training in the sport, and self-selection of sports that may appear to minimize the triggering of asthma.{{an num|Olympics|26}} {{an|athletes}} It has also been suggested that some professional athletes who do not suffer from asthma claim to do so in order to obtain special permits to use certain performance-enhancing drugs.

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