Chronic bronchial asthma from challenge to treatment: epidemiology and social impact.

Asthma is an important cause of chronic morbidity and a crucial health problem among children and adults worldwide, with high prevalence rates particularly in many developed countries.Increasing morbidity, hospital admission rates, use of medical services, drug use and, in some countries, increasing mortality rates have been reported.3 However, controversy still exists regarding the epidemiology of asthma. There are two serious problems which need to be considered when trying to obtain reliable data on the prevalence, morbidity, and mortality of asthma. The first relates to definition; despite substantial advances in understanding the pathogenesis, genetics, and clinical characteristics of asthma, we do not have a useful definition of asthma for epidemiological purposes.2 The second problem concerns the different methods used to collect epidemiological data and information. More recently two international studies—the European Community Respiratory Health Survey (ECRHS)4 and the International Study of Asthma and Allergies in Childhood (ISAAC)5—have used the same internationally standardised questionnaire to provide important data on the prevalence of asthma.