Asthma surveillance in the United States. A review of current trends and knowledge gaps.

sthma is a common malady, affecting persons of all ages. Much of ur understanding of the natural history of this condition has come from comlnunity-based studies,12 including the Harvard Six Cities Study, discussed elsewhere in this issue (see article by Speizer, this issue). However, information on prevalence of asthma, mortality due to asthma, and the impact of the disease in the US population comes from national population-based data systems maintamed by the National Center for Health Statistics (NCHS) of the CDC.3 Data on asthma can be found in a number of these data systems. These systems include interview surveys (the National Health Interview Survey, NHIS), examination surveys (the National Health and Nutrition Examination Survey, NHANES), record-based surveys (the National Hospital Discharge Survey, NHDS, and the National Ambulatory Medical Care Survey, NAMCS), and the mortality data from the National Vital Statistics System (NVSS). Through the combined information provided by these data