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1 Major Issues in Understanding Asthma
Pages 19-38

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From page 19... ... It also addresses some of the major issues in understanding the medical condition called asthma: the controversy over the definition of the illness; the characteristics of its clinical presentation in children, adolescents, and adults; and the concepts of the "development of asthma" and "exacerbations of asthma." Finally, the chapter presents brief discussions of four topics addressed in greater detail later in the report: risk factors, trends in prevalence, pathophysiology, and tools for evaluating the effectiveness of interventions to reduce asthma. ORIGIN OF THE STUDY In 1993, as a result of joint funding between the U.S. Read the entire page →
From page 20... ... At about the same time, IAD and the EPA Office of Research and Development issued a major assessment of the health impacts of environmental tobacco smoke (ETS) , which found a correlation between exposure to ETS and asthma in children. Read the entire page →
From page 21... ... Although some of these conclusions address medical conditions and topics outside the scope of the present report, several address issues related to asthma and the impact of indoor air ex posures. The Indoor Allergens committee recommended that steps be taken to improve estimates of allergenic disease incidence and prevalence, and to establish effective mechanisms for medical professionals to acquire assessments of potential exposure to indoor allergens in residential environments. Read the entire page →
From page 22... ... In susceptible individuals, this inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning. These episodes are usually associated with widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment. Read the entire page →
From page 23... ... Discovering the origin or origins of the inflammatory response, however, remains a critical unanswered question for researchers. The absence of a universally accepted definition of asthma makes it especially difficult to arrive at a consistent operational definition for epidemiologic studies. Read the entire page →
From page 24... ... The agents most often associated with these respiratory infections are common viral respiratory pathogens (Busse, 1989,1995; Folkerts and Nijkamp, 1995; Martinez, 1995; Pattemore et al., 1992) Read the entire page →
From page 25... ... A family history of asthma and allergy and a personal atopic predisposition increase the likelihood that asthma will develop (Brooke et al., 1995; Martinez et al., 1995; Williams and McNicol, 1969~. With asthma symptoms ranging from clearly episodic to nearly continuous, from mild to severe, and from an isolated cough to a loud wheeze, diagnosing patients accurately can prove to be very difficult. Read the entire page →
From page 26... ... Because of the length of time required, there have been few prospective studies of the risk of asthma recurring once remission has occurred; hence there is no information about risk factors for redeveloping asthma. As children move into adolescence and adulthood, respiratory infections remain a common cause of symptomatic episodes (Busse, 1995; Martinez, 1995~. Read the entire page →
From page 27... ... A final important concern about the progression of asthma throughout life is the relationship between asthma and chronic obstructive pulmonary disease. As mentioned earlier, the chronic inflammatory process of asthma appears to ultimately result in Read the entire page →
From page 28... ... The contribution of indoor sources of allergens and irritants to respiratory disease is important because chronic obstructive pulmonary disease is an important cause of increased morbidity and mortality among adults. RISK FACTORS FOR ASTHMA As early as the 1920s, studies demonstrated that a familial predisposition to asthma existed, suggesting that genetics may play a role in asthma development. Read the entire page →
From page 29... ... Also since 1992, NCHS has gathered annual data on hospital emergency and outpatient department visits. Hospitalizations attributable to asthma were estimated from 1979 to 1994 from the National Hospital Discharge Survey. Read the entire page →
From page 30... ... In 1993-1994, the age-adjusted asthma hospitalization rates were higher in the Northeast than in the West. In each time interval examined, the hospitalization rates were highest among children 0-4 years, lowest among persons aged 15-34 years, and intermediate for those 235. Read the entire page →
From page 31... ... The critical difference is that in persons with allergic asthma, inhalation of allergens initiates an inflammatory response that leads to hyperreactivity of the airways and symptoms of asthma. In persons with nonallergic asthma, the inflammatory process and airway hyperreactivity appear the same as in individuals with allergic asthma, but allergic responses, defined by the presence of immunoglobulin E (IgE) Read the entire page →
From page 32... ... The development of nonallergic asthma is somewhat harder to explain, although there are suggestions that chronic infections may be related to asthma in some nonallergic individuals (von Hertzen et al., 1999~. As in the case of allergic asthma, inflammation occurs in the lungs and is typically accompanied by airway Hyperreactivity A variety of exposures may lead to wheezing in the nonallergic asthmatic; however, the origin of the inflammation cannot be directly identified. Read the entire page →
From page 33... ... It is possible that the inflammatory response that started as an allergic response in a child may become self-perpetuating by adulthood even as the allergic sensitization is lost. It is also possible that these are two different disease processes that merely have similar clinical appearances. Read the entire page →
From page 34... ... These measures could include some attempt at estimating Jung inflammation, determining allergen-specific IgE levels in serum, or assessing exer cise tolerance. Read the entire page →
From page 35... ... American Journal of Respiratory and Critical Care Medicine 152~6 Pt 1~:1872-1878. Read the entire page →
From page 36... ... American Journal of Respiratory and Critical Care Medicine 151~5~:1644-1648. Martinez FD, Wright AL, Taussig LM, Holberg CJ, Halonen M, Morgan WJ.1995. Read the entire page →
From page 37... ... American Journal of Respiratory and Critical Care Medicine 157~4 Pt 1~:1079-1084. von Hertzen L, Toyryla M, Gimishanov A, Bloigu A, Leinonen M, Saikku P Read the entire page →
From page 38... ... American Journal of Respiratory and Critical Care Medicine 154~1~:237-243. Yunginger JW, Reed CE, O'Connell EJ, Melton LJ III, O'Fallon WM, Silverstein MD. Read the entire page →

From page 19...

... It also addresses some of the major issues in understanding the medical condition called asthma: the controversy over the definition of the illness; the characteristics of its clinical presentation in children, adolescents, and adults; and the concepts of the "development of asthma" and "exacerbations of asthma." Finally, the chapter presents brief discussions of four topics addressed in greater detail later in the report: risk factors, trends in prevalence, pathophysiology, and tools for evaluating the effectiveness of interventions to reduce asthma. ORIGIN OF THE STUDY In 1993, as a result of joint funding between the U.S.

1 Major Issues in Understanding Asthma Pages 19-38

1 Major Issues in Understanding Asthma
Pages 19-38