Epidemiology of asthma: the year in review

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.