Assessment of body composition in elderly:: Accuracy of bioelectrical impedance analysis

Background: In the literature there are several body impedance analysis (BIA) prediction equations generally determined in younger populations and their accuracy in the elderly has not been adequately confirmed. Objective: We verified the reliability of the BIA method in a body composition study in the elderly. Methods:To assess the accuracy of bioelectrical impedance analysis we compared this method with dual photon absorptiometry (DPA), assumed as a gold standard; body composition was predicted by seven BIA prediction equations in 24 healthy elderly individuals. Results:The best equation in fat-free mass (FFM) estimation is the RJL System formula (published by Segal in 1988); nevertheless, the wide range of the error in FFM estimating may limit its clinical application. The FFM hydration variability seems to be the principal variable which explains the error in FFM estimation by BIA prediction equations. Conclusion: These findings indicate that the use of BIA equations is not interchangeable, when FFM is calculated in an elderly population, and more validation studies are necessary in this age group to evaluate the clinical application of this method.