BIOELECTRICAL-IMPEDANCE ANALYSIS MEASUREMENTS AS PART OF A NATIONAL NUTRITION SURVEY

Since 1960 the National Center for Health Statistics has conducted sev en national health examination surveys. All surveys included anthropom etry. As the relations between various chronic diseases and body compo sition have been recognized, there has been considerable interest in a ssessing body composition in health examinations on the basis of natio nally representative probability samples. I focus on considerations th at influenced the decision to include bioelectrical impedance analysis (BIA) in a national nutrition survey. Tetrapolar, single-frequency (5 0 kHz) BIA was included in the third National Health and Nutrition Exa mination Survey (1988-1994) for persons aged greater than or equal to 12 y, resulting in > 17 000 resistance and reactance measures in non-H ispanic white, non-Hispanic black, and Mexican American subjects. The usefulness of these data in producing national reference distributions for lean body mass and fat mass, however, is currently limited by the uncertain availability of generalizable, valid, reliable, cross-valid ated prediction equations for various age, sex, and racial-ethnic grou ps.