Accurate assessment of the prevalence of asthma has been hindered by varying definitions of asthma and methods of data collection, each combining to make data comparison across studies difficult. Following a brief discussion about the definition of asthma and the identification of affected individuals, studies of asthma prevalence are reviewed. The definition, diagnosis, and treatment of asthma are discussed in detail elsewhere. (See "Diagnosis of asthma in adolescents and adults" and "An overview of asthma management".)
Essential to any study of prevalence are the definition of the disease being studied and the methods available to identify affected individuals. Although many definitions and methods of data collection have been used and reported, herein we discuss the most common.
Definition — A definition of asthma that incorporates both a positive test of airway hyperresponsiveness and symptoms was proposed and tested for epidemiologic purposes . The study defined "current asthma" as bronchial hyperresponsiveness (BHR) in the presence of wheezing in the 12 months prior to the study. According to this definition:
●"Current asthma" identified a group of children with more severe BHR, greater peak flow variability, more symptoms, more atopy, and more medication use than children with BHR alone or wheeze alone
●Children who only had wheeze did not differ from the normal group except in reporting symptoms and in more associated use of asthma medications