地域高齢者のサルコペニア指標と筋力・身体機能

地域在住高齢者でサルコペニア指標と筋力、身体機能との関連をみた論文を紹介します。

Merriwether EN, Host HH, Sinacore DR. Sarcopenic indices in community-dwelling older adults. J Geriatr Phys Ther. 2012 Jul-Sep;35(3):118-25. doi: 10.1519/JPT.0b013e31823c4bef.

筋肉量はDEXAで測定して、四肢除脂肪体重÷身長÷身長(ALM/ht²)と骨格筋指数(SMI)でサルコペニアの有無を評価しています。身体機能はmodified Physical Performance Testと歩行速度、下肢筋力は等速性筋力計で評価しました。

結果ですが、ALM/ht²では49％がサルコペニア、SMIでは84％がサルコペニアと判定されました。ALM/ht²のほうがSMIより下肢筋力と有意な関連を認めましたが、両者とも身体機能とは有意な関連を認めませんでした。

下肢筋力と身体機能には有意な相関があったことを考えると、身体機能の予測因子としては筋肉量より筋力のほうが優れているという結論です。

平均年齢82.4歳の高齢者とはいえ、筋肉量低下で84％がサルコペニアと判定されるのは行きすぎだと思います。49％ならわかりますが。また、現在では筋肉量低下単独でサルコペニアと判定することは少なくなっていますので、84％の高齢者の一部は実際にはサルコペニアではないのでしょう。

Abstract

BACKGROUND:

Sarcopenic (SP) indices are used to estimate loss of skeletal lean mass and function and to determine the prevalence of SP in older adults. It is believed that older women and men with lower skeletal lean mass will be weaker and have more functional limitations.

PURPOSE:

(1) To classify community-dwelling older adults using 2 common SP indices: appendicular lean mass/height² (ALM/ht²) and skeletal muscle index (SMI), and (2) to determine each indices value as indicators of lower extremity strength and physical function.

METHODS:

The sample consisted of 154 community-dwelling older adults (111 women and 43 men; mean age = 82.4, SD = 3.6 years; mean body mass index = 25.8, SD = 4.4 kg/m). Each underwent whole-body dual-energy x-ray absorptiometry to assess lean mass. The 9-item modified Physical Performance Test and self-selected walking speed were used to evaluate function. Lower extremity strength was measured bilaterally using isokinetic dynamometry.

RESULTS:

The ALM/ht² index classified 75 participants (49%) as SP and 79 (51%) as nonsarcopenic (NSP). The SMI classified 129 participants (84%) as SP and 25 (16%) as NSP. There were no differences in functional measures between groups by gender using either index after classification. The ALM/ht index was more strongly correlated with peak torque of all lower extremity muscle groups (r = 0.276-0.487) compared with the SMI (r = 0.103-0.344). There was no relationship between SP index and physical function.

DISCUSSION:

There were marked differences in how 2 SP indices classified community-dwelling older adults. Lower extremity strength was lower in older women classified as SP than NSP using the ALM/ht index, but LE strength was not different in older men. However, no lower extremity strength differences were observed between SP and NSP men or women using the SMI classification. None of the SP index uniformly identified community-dwelling older adults with functional or strength deficits.

CONCLUSIONS:

Detection of strength deficits using SP indices alone may be gender-specific and may not reflect strength or functional decline in community-dwelling men aged 80 years or older. Given associations between lower extremity strength and physical function, strength measures remain a better predictor of physical performance than SP indices for community-dwelling older men and women.