J. P. ALLARD, E. ADHDASSI, M. MCARTHUR, A. MCGEER, A. SIMOR AND B. LIU. Department of Medicine, University of Toronto, Toronto, M5G-2C4.

This study compared bioelectric impedance analysis (BIA) with anthropometry for determination of total body fat (TBF), in 448 elderly living in long term care facilities to evaluate the usefulness of BIA as adjuncts to assessment of nutritional status and body composition in elderly. Weight (62.55± 0.66 kg), height (160.52± 0.51 cm), tricep (21.52± 0.40 MM) and subscapular skinfold thicknessess (21.59± 0.40 mm), age (84.02± 0.39 y) and sex (148 men, 300 women) were used to derive TBF. Body density was calculated from logarithm of skinfold thickness according to Durnin and Womersley, adapted for age and sex. Then, Siri’s equation was used to derive the TBF. Resistance (538.2± 5.1) and reactance (52.10± 1.73) were measured with a four terminal impedance plenthysmograph (RJL system, Detroit); from these data plus height, weight, and sex, lean body mass (LBM) was derived and TBF was calculated. Using the paired t-test, a significant difference was seen in TBF determined by the different methods (TBF-anthropometry: 20.10± 0.36 kg vs TBF-BIA: 17.21± 0.50 kg, P=0.0001). However, there was a strong and significant correlation between the two methods (r=0.774, P=0.0001). A comparison of differences between methods for individual subjects show that, the anthropometric method overestimated TBF measured by BIA by a mean of 2.90 kg with an error of 0.85 kg. Since BIA is inexpensive, has a lower precision error and gives reliable readings with different untrained observers, it is a better method for use in measuring body composition in elderly because it makes few physical demands on the subjects. In addition, prediction equations based on BIA have been validated in the elderly. This study was supported by Medical Research Council.

Presented at:

EXPERIMENTAL BIOLOGY 99TH CONFERENCE, Washington, DC, April 1999.

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