Yamada Yosuke, Masuo Yoshihisa, Yokoyama Keiichi, Hashii Yukako, Ando Soichi, Okayama Yasuko, Morimoto Taketoshi, Kimura Misaka, Oda Shingo
Laboratory of Sports Science and Human Motor Control, Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
Eur J Appl Physiol. 2009 Sep;107(2):135-44. doi: 10.1007/s00421-009-1106-6. Epub 2009 Jun 17.
Bioelectrical impedance analysis (BIA) is an affordable, non-invasive, easy-to-operate, and fast alternative method to assess body composition. However, BIA tends to overestimate the percent body fat (%BF) in lean elderly and underestimate %BF in obese elderly people. This study examined whether proximal electrode placement eliminates this problem. Forty-two elderly men and women (64-96 years) who had a wide range of BMI [22.4 +/- 3.3 kg/m(2) (mean +/- SD), range 16.8-33.9 kg/m(2)] and %BF (11.3-44.8%) participated in this study. Using (2)H and (18)O dilutions as the criterion for measuring total body water (TBW), we compared various BIA electrode placements; wrist-to-ankle, arm-to-arm, leg-to-leg, elbow-to-knee, five- and nine-segment models, and the combination of distal (wrists or ankles) and proximal (elbows or knees) electrodes. TBW was most strongly correlated with the square height divided by the impedance between the knees and elbows (H(2)/Z (proximal); r = 0.965, P < 0.001). In the wrist-to-ankle, arm-to-arm, leg-to-leg, and five-segment models, we observed systematic errors associated with %BF (P < 0.05). After including the impedance ratio of the proximal to distal segments (P/D) as an independent variable, none of the BIA methods examined showed any systematic bias against %BF. In addition, all methods were able to estimate TBW more accurately (e.g., in the wrist-to-ankle model, from R(2) = 0.90, SEE = 1.69 kg to R(2) = 0.94, SEE = 1.30 kg). The results suggest that BIA using distal electrodes alone tends to overestimate TBW in obese and underestimate TBW in lean subjects, while proximal electrodes improve the accuracy of body composition measurements.
生物电阻抗分析（BIA）是一种经济实惠、非侵入性、易于操作且快速的评估身体成分的替代方法。然而，BIA往往会高估瘦体重老年人的体脂百分比（%BF），而低估肥胖老年人的%BF。本研究探讨了近端电极放置是否能消除这一问题。42名年龄在64至96岁之间的老年男性和女性（BMI范围为[22.4±3.3kg/m²（平均值±标准差），范围为16.8至33.9kg/m²]，%BF范围为11.3至44.8%）参与了本研究。以氘（²H）和氧-18（¹⁸O）稀释法作为测量总体水（TBW）的标准，我们比较了各种BIA电极放置方式；腕至踝、臂至臂、腿至腿、肘至膝、五段和九段模型，以及远端（手腕或脚踝）和近端（肘部或膝盖）电极的组合。TBW与身高平方除以膝盖和肘部之间的阻抗（H²/Z（近端））相关性最强（r = 0.965，P < 0.001）。在腕至踝、臂至臂、腿至腿和五段模型中，我们观察到与%BF相关的系统误差（P < 0.05）。将近端与远端节段的阻抗比（P/D）作为自变量纳入后，所检查的任何BIA方法均未显示出对%BF的任何系统偏差。此外，所有方法都能够更准确地估计TBW（例如，在腕至踝模型中，从R² = 0.90，标准误（SEE） = 1.69kg提高到R² = 0.94，SEE = 1.30kg）。结果表明，仅使用远端电极的BIA往往会高估肥胖受试者的TBW，而低估瘦体重受试者的TBW，而近端电极可提高身体成分测量的准确性。
