Asthma is a worldwide problem, with more than 17 million persons in the United States estimated to have asthma, and there is evidence that the prevalence is increasing. This article reviews the latest epidemiologic evidence for an increase in asthma prevalence and morbidity, and the evidence that environment plays a significant role in this disease. This review focuses on five specific areas: prevalence, incidence, natural history, environmental factors, and morbidity and mortality.
Asthma is a worldwide problem and there is evidence that the prevalence is increasing, but there are still insufficient data to determine the likely causes for this increase. Epidemiologic studies are the only way in which the risk factors associated with this disease can be measured in populations. Knowledge of prevalence and risk factors is important for resource allocation, for the design of interventions, and for the prevention of the development of disease at an early stage.
Asthma is defined as a clinical syndrome characterized by airway inflammation, variable lung function, and airways responsiveness [1]. Epidemiologic studies are hindered by having no clear definition of asthma, as there is no clinically accepted method for measuring inflammation, and it is unlikely that one will be possible until more is known about the pathogenesis of the condition. Despite these problems, in both clinical evaluation and epidemiologic research, asthma-like symptoms and the presence of atopy are heavily relied on to establish the diagnosis.