Epidemiology of asthma in childhood.

The epidemiology of asthma in childhood is undergoing changes in many parts of the world. Prevalence, rates of hospitalization and mortality are all on the rise. In the United States, urban dwellers and minorities have experienced the greatest acceleration in rates. Elsewhere, some countries have experienced large increases in asthma morbidity and mortality, while others have not. Inconsistency in defining asthma and variations in methodology complicate epidemiologic investigation, but recent studies confirm the disturbing trend toward increased morbidity and mortality from childhood asthma and offer some insights into possible contributing factors.