Measuring childhood asthma prevalence before and after the 1997 redesign of the National Health Interview Survey--United States.

Asthma is the most common chronic disease of childhood and a leading cause of disability among children (1,2). Since 1980, asthma prevalence has increased dramatically in children (3,4). The National Health Interview Survey (NHIS), the principal source of asthma prevalence data for the United States, was redesigned in 1997. This report presents NHIS data from 1980-1998 to examine the effect of the redesign on measuring trends in asthma prevalence overall and among age and racial subgroups of children. The findings indicate that although asthma prevalence estimates for 1997-1998 are lower than those preceding changes in the survey design, estimates after 1997 are not comparable to previous estimates. Additional data are needed to establish a new trend after 1997.