Epidemiology of asthma in childhood - An international comparison.

Asthma is one of the most common childhood diseases and is important both from a medical as well as an economic standpoint. Information about the frequency of asthma varies greatly, and there are many factors that make a comparison of the more than 140 studies from around the world difficult. Since the 1980's in Germany there have been many estimates of asthma prevalence, which depending on the definition of asthma give a lifetime prevalence of 5 - 10% among children. Despite many methodologic problems in comparisons of available studies, it appears based on available data that asthma is becoming more prevalent worldwide, and there are no clear explanations for this phenomenon. Possible factors include improved survival of preterm babies, changes in exposure to allergens, influence of pollutants, changes in medical care or other unknown causes.