Prevalence and etiology of asthma

An increased understanding of the causes of asthma is coming from the inter national comparisons of asthma prevalence particularly those from the Europ ean Community Respiratory Health Survey of asthma prevalence in adults and the International Study of Asthma and Allergies in Childhood. From these an d other studies of asthma prevalence, it is possible to draw some tentative conclusions as to the patterns of asthma prevalence worldwide, There are f ive striking patterns: first, asthma prevalence is increasing worldwide; se cond, asthma is generally more common in Western countries and less common in developing countries; third, asthma is more prevalent in English-speakin g countries; fourth, asthma prevalence is increasing in developing countrie s as they become more Westernized or communities become urbanized: and fift h, the prevalence of other allergic disorders may also be increasing worldw ide. These five key features of the international patterns of asthma preval ence raise major questions about the role of "established" risk factors for the development of asthma, As a result, recent research has expanded to in clude the study of novel factors that may "program" the initial susceptibil ity to sensitization or contribute to the development of asthma independent of atopic sensitization. These include various exposures in utero, which a re reflected in various perinatal factors measured at birth, and exposures (or lack of exposures) in the early years of life that may make the infant more susceptible to the subsequent development of asthma, These issues are now the focus of an intensive research effort worldwide, and the next few g ears are likely to see exciting advances in our understanding of the causes of asthma.