MEASURING THE BODY-COMPOSITION OF ELDERLY SUBJECTS - A COMPARISON OF METHODS

There is a paucity of data on differences between methods for the asse ssment of body composition in elderly subjects. Studies on younger adu lts suggest that such differences are of some practical significance a t the individual level. In the present study the following methods of estimating percentage body fatness (BF%) were compared in healthy elde rly men and women (mean age 70 (SD 6) years: densitometry; skinfold th ickness; total body water; bioelectrical impedance (BIA) using an age- specific predictive equation and the manufacturers' equation; body mas s index (BMI). Though BF% estimates from the various methods tended to be highly correlated with those from densitometry and with each other , differences between methods at the individual level were marked. In particular, the age-specific equations based on BMI and BIA systematic ally overestimated BF% relative to the other methods. Biases between B F% estimates derived from densitometry, skinfolds, BIA (manufacturers' equation) and total body water were less marked, indicating little ev idence of systematic differences between these methods in elderly subj ects. Individual differences between methods were slightly greater tha n those reported in some studies of younger adults, but this may be of little practical significance, and may be considered inevitable in vi ew of variability between and within subjects in the extent to which t he underlying assumptions of these two-component methods are met in el derly subjects.