Archivos Latinoamericanos de Nutrición (Dec 2008)
Utilização da impedância bioelétrica para estimativa da massa muscular esquelética em homens idosos Use of bioelectrical impedance for the estimation of skeletal muscle mass in elderly men
Abstract
O presente estudo tem como objetivos: a) verificar a concordância entre os métodos da impedância bioelétrica (BIA) e da absortometria radiológica de dupla energia (DEXA), para a estimativa da massa muscular esquelética (MME); b) analisar o poder preditivo das variáveis antropométricas e de BIA para predição da MME em idosos. Foram avaliados 60 homens idosos (61 a 80 anos), residentes na região Sul do Brasil. Mensuraram-se as variáveis antropométricas (massa corporal e estatura), as variáveis de resistência e hidratação dos tecidos livres de gordura foram medidas pela técnica da BIA tetrapolar (Biodinamics - BF-310), realizou-se também um scan de corpo inteiro através da DEXA (LUNAR PRODIGY DF + 14319 Radiation e software 7.52.002 DPX-L). A diferença entre os métodos foi verificada pelo teste “t”, análise dos resíduos e o coeficiente de correlação. O valor preditivo das variáveis antropométricas e de BIA foi verificado pela regressão Linear Múltipla. Observou-se que a BIA superestimou em média 0,6 kg (dp= 1,59) a MME, quando comparada com a DEXA, contudo não houve diferença estatística (pThe aim of the present study was twofold: a) to determine the agreement between bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DEXA) for the estimation of skeletal muscle mass (SMM), and b) to analyze the predictive power of anthropometric variables and BIA for the prediction of SMM in the elderly. Sixty elderly men (61 to 80 years) from the southern region of Brazil were studied. Anthropometric variables (body weight and height) were measured, the resistance and hydration of fat-free tissues variables were determined by tetrapolar BIA (BF-310, Biodynamics). A whole body DEXA scan was also performed (Lunar Prodigy DF + 14319 Radiation and 7.52.002 DPX-L software). Differences between methods were analyzed using the t-test, analysis of residues and correlation coefficient. The predictive value of the anthropometric variables and BIA was evaluated by multiple linear regression. BIA overestimated SMM on average by 0.60 kg (sd=1.59) when compared to DEXA, however, no statistical difference was observed (p>0.05). There was a strong correlation between methods (r=0.90; p<0.01). Regression analysis demonstrated that the Ht²/R variable explained 86% of the variation in SMM when adjusted for body weight and age, and this relationship did not depend on body fat, hydration of fat-free tissues or BMI. Thus, BIA as tested here is a valid method for the estimation of SMM in elderly men and its values can be best predicted using the regression model proposed, which included Ht²/R adjusted for body weight and age.
