Body composition in underweight elderly subjects: reliability of bioelectrical impedance analysis.
OBJECTIVE
In underweight elderly subjects it is important to estimate body composition and particularly fat-free mass (FFM). Bioelectrical impedance analysis (BIA) is a non-invasive method in determining FFM, but its usefulness in these frail subjects should be verified. The aim of this study is to verify in underweight elderly people the reliability of previously published BIA formulas in detecting FFM.


METHODS
Fifty-seven hospitalized elderly subjects (27 males and 30 females) with body mass index <20 kg/m(2) were selected. In all subjects, FFM was detected by dual energy X-ray absorptiometry. Moreover, BIA measurements were performed at standard frequency (50 kHz and 800 microA) and FFM was derived using the main previous published BIA equations.


RESULTS
In men, Kyle and Rising equations gave acceptable estimates of FFM with a mean error, respectively, of 1+/-1.9 and 1.4+/-1.7 kg. Also RJL formula could be used after adjusting for a correction factor. In women, no equation seemed sufficiently reliable to estimate FFM.


CONCLUSIONS
BIA method seems useful to evaluate body composition in underweight elderly men but it seems to have intrinsic limits in women. Nevertheless, the variability in behavior of the different equations suggests to be careful in adopting BIA equations.
Lupoli
Lucia
L
Department of Medical and Surgical Sciences, Division of Geriatrics, University of Padua, Padova, Italy.
Sergi
Giuseppe
G
Coin
Alessandra
A
Perissinotto
Egle
E
Volpato
Stefania
S
Busetto
Luca
L
Inelmen
E M Emine Meral
EM
Enzi
Giuliano
G
D015502:Absorptiometry, Photon / Q000379:methods; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D044342:Malnutrition; D008433:Mathematics; D018482:Muscle, Skeletal / Q000502:physiology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity