筋肉量と身体機能の関連

筋肉量と身体機能の関連を筋力低下のある高齢者で調査した論文を紹介します。

Kyoung-Eun Kim, et al: Relationship between muscle mass and physical performance: is it the same in older adults with weak muscle strength? Age Ageing (2012) doi: 10.1093/ageing/afs115 First published online: August 21, 2012

筋肉量はDEXAで評価して、四肢筋肉量を体重で割ったものと、身長の2乗で割ったものを指標としています。身体機能はShort Physical Performance Batteryで評価しています。

膝伸展筋の筋力で、低筋力群（25パーセンタイル以下）と高筋力群（75パーセンタイル以上）に分類しています。

結果ですが、低筋力群では筋肉量と身体機能に有意な相関を認めませんでした。一方、高筋力群では筋肉量より筋力のほうが身体機能とより有意な相関を認めました。以上より、筋力低下のある高齢者では筋肉量と身体機能に関連を認めず、筋力評価がより重要という結論です。

こうなると筋肉量単独の評価より、やはり筋力と身体機能も含めて評価したうえでサルコペニアを判断して、その介入方法を検討することが重要なのだと感じます。とはいえ筋肉量の評価も重要だとは思いますが。

Abstract

Background: the relationship between muscle mass and physical performance has not been consistent among studies.

Objective: to clarify the relationship between muscle mass and physical performance in older adults with weak muscle strength.

Design: cross-sectional analysis using the baseline data of 542 older men and women from the Korean Longitudinal Study on Health and Aging.

Methods: dual X-ray absorptiometry, isokinetic dynamometer and the Short Physical Performance Battery (SPPB) were performed. Two muscle mass parameters, appendicular skeletal mass divided by weight (ASM/Wt) and by height squared (ASM/Ht²), were measured. We divided the participants into a lower-quartile (L25) group and an upper-three-quartiles (H75) group based on the knee-extensor peak torque. Correlation analysis and logistic regression models were used to assess the association between muscle mass and low physical performance, defined as SPPB scores <9 after="after" confounders.="confounders." controlling="controlling" for="for" p="p">

Results: in the L25 group, no correlation between mass and SPPB was detected, whereas the correlation between peak torque and SPPB was significant and higher than that in the H75 group. Results from the logistic models also showed no association between muscle mass and SPPB in the L25 group, whereas muscle mass was associated with SPPB in the H75 group.

Conclusion: muscle mass was not associated with physical performance in weak older adults. Measures of muscle strength may be of greater clinical importance in weak older adults than is muscle mass per se.