PREDICTION OF BODY-COMPOSITION IN ELDERLY MEN OVER 75 YEARS OF AGE

A comprehensive number of body composition predictions (involving weig ht, height, skinfold thicknesses, bioelectrical impedance and near-inf rared interactance-NIRI) were evaluated against total body water (TBW from isotope dilution), in 23 randomly selected men over 75 years old, and dual-energy X-ray absorptiometry (DXA), in 15 volunteers from thi s group. Comparisons were made between anthropometric and impedance me thods for estimating limb muscle mass (obtained using DXA). Bias and 9 5% limits of agreement between measured TBW and DXA estimates were -2. 1 kg and 3.1 kg, respectively (for fat, 5.4% and 6.1% body weight). Ag reement between TBW predictions and reference measurements was remarka bly variable, irrespective of whether TBW was predicted from TBW-speci fic equations or indirectly from estimates of fat or fat-free mass: fo r predictions using anthropometry, bias ranged from -4.7 kg to 1.6 kg and 95% limits of agreement from bias +/- 3.8 kg to +/- 5.0 kg; using impedance, bias was -8.8 kg to 3.2 kg and 95% limits of agreement were bias +/- 3.6 kg to +/- 7.8 kg; corresponding values for NIRI were -5. 3 kg and +/- 5.4 kg. Although some non-age-specific equations appeared valid, age-specific equations generally predicted TBW better. Limb mu scle mass (DXA) was predicted better using the segmental impedance met hod, from indices of limb muscle area (r = 0.76; SEE = 1.9 kg) and vol ume (r = 0.86; SEE = 1.6 kg), than by anthropometry alone (r = 0.61 an d 0.71; SEE = 2.3 kg and 2.1 kg, respectively). In conclusion, some bo dy composition predictions are unacceptable (at least for TBW) in olde r men, and care is recommended when selecting from these methods or eq uations. Also, the segmental impedance method is as good as, if not be tter than, anthropometry alone in predicting limb muscle mass (DXA) in older men.