Asthma prevalence rose rapidly through the 1980s and 1990s. Asthma period prevalence increased among children 0-17 years of age from 3.6 percent in 1980 to a peak of 7.5 percent in 1995. During the period 1980-1996, asthma prevalence increased on average more than 4% per year. The reasons for this increase are not well understood, but this "asthma epidemic" has spurred research and debate about its causes, and it has prompted increased intervention and prevention efforts. Due to the rising prevalence and the associated costs, interest has focused on recent asthma prevalence trends.

(For information on trends in childhood asthma, see references 4 and 5)