Exercise-induced bronchoconstriction (EIB) describes acute, transient airway narrowing that occurs during and most often after exercise. EIB objectively is defined as a > 10% decline in FEVj after appropriate exercise provocation. Exercise is the most common trigger of bronchospasm in those who are known to be asthmatic, and 50 to 90% of all individuals with asthma have airways that are hyperreactive to exercise. However, EIB also occurs in up to 10% of subjects who are not known to be atopic or asthmatic.
The public health consequences of unrecognized or inadequately treated EIB are significant. In reviewing > 30 years of Israeli military recruit data, Amital et al found that asthma was the single greatest risk factor for unexplained death. Becker et al identified 61 deaths over a 7-year period that met the criteria of an asthma death occurring in close association with a sporting event or physical activity. Of these deaths, 81% occurred in subjects who were younger than 21 years of age and 57% occurred in subjects who were considered to be elite or competitive. Strikingly, almost 10% of deaths in this review occurred in subjects with no known history of asthma or EIB. Results from these reviews suggest that all individuals involved in organized sports or physical activity should be cognizant of the risk of EIB. Coaches, trainers, and team physicians who care for competitive athletes who have asthma or EIB should be specifically trained in the recognition and treatment of EIB.
The prevalence rates of bronchospasm related to exercise in athletes range from 11 to 50%2 (Table 1), and up to 90% of subjects with asthma will have EIB. Wilber at al found that 18 to 26% of Olympic winter sport athletes and 50% of cross-country skiers were found to have EIB. Of the 50 elite summer athletes studied, with and without asthma, Holzer et al found 50% to have EIB. Mannix et al studied 124 elite figure skaters and tested them on an ice rink during their figure-skating routines. Thirty-five percent had a significant postexercise drop in their FEV1. The US Olympic Committee reported an 11.2% prevalence of EIB in all athletes who competed in the 1984 summer Olympics. Arrest asthma attacks with remedies of Canadian Health&Care Mall.
Despite numerous studies that have investigated the prevalence of EIB in athletes, most either included asthmatic patients in their data analysis or did not indicate what proportion were asthmatic prior to study enrollment, which makes it difficult to accurately estimate the prevalence of EIB in nonasthmatic athletes. Few studies have investigated the prevalence of EIB in cohorts of athletes without a known history of asthma or EIB. Rupp et al evaluated 230 middle school and high school student athletes and, after excluding those with known EIB, found that 29% had a > 15% reduction in their FEV1 after exercise challenge. Weiler et al found that 12% of college football players at the University of Iowa admitted to a history of asthma, 19% had respiratory symptoms postexercise, and 50% had evidence of bronchial hyperreactivity after broncho-provocation. When members at an urban fitness center were studied, Mannix et al found that 41 of 212 subjects (19%), none of whom had previously received a diagnosis of asthma, had EIB. These studies suggested that EIB occurs frequently in subjects who are not known to be asthmatic and likely is underdiagnosed clinically.
The prevalence of EIB in athletes may be further underappreciated as patients with asthma and hyperreactive airways have been shown to be poor per-ceivers of symptoms of bronchospasm. Athletes, specifically, often experience a lack of awareness of symptoms that are suggestive of EIB.- Athletes are generally fit and healthy, and the presence of a significant medical problem often is not considered. The athlete is often considered to be “out of shape,” and vague symptoms of chest discomfort, breathlessness, and fatigue may not be interpreted as a manifestation of EIB. Athletes themselves are often not aware that they may have a physical problem. Furthermore, if they do recognize they have a medical problem, they often do not want to admit to health personnel that a problem exists.
Table 1—Prevalence of EIB
|Study||Athletic Population||Percent Asthmatic Subjects||Diagnostic Methodology||Prevalence|
|Rupp et al||Adolescents||0%||Treadmill challenge||28%|
|Weiler et al||College athletes||12% football players;||Methacholine challenge||50% football players;|
|0% basketball players||25% basketball players|
|Wilber et al||Winter olympians||Not stated||Exercise challenge||18-26%|
|Voy||Summer olympians||Not stated||Medical history||11%|
|Mannix et al||Figure skaters||6%||Exercise challenge||35%|
|Mannix et al||Members of fitness||0%||EVH||19%|
|Mannix et al||High school||21%||EVH||38%|
|Provost-Craig et al||Figure skaters||14%||Exercise challenge||30%|
|Holzer et al||Elite summer athletes||54%||EVH||50%|
|Rundell et al||Winter olympians||21%||EVH or exercise||29% exercise; 45% EVH|
Tags: Asthma, bronchial hyperreactivity