サルコペニア、ダイナペニア、筋肉の質のレビュー

サルコペニア、ダイナペニア、筋肉の質に関するレビュー論文を紹介します。

Mitchell WK, Williams J, Atherton P, Larvin M, Lund J, Narici M. Sarcopenia, dynapenia, and the impact of advancing age on human skeletal muscle size and strength; a quantitative review. Front Physiol. 2012;3:260. Epub 2012 Jul 11.

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http://www.frontiersin.org/Striated_Muscle_Physiology/10.3389/fphys.2012.00260/abstract

サルコペニアよりもダイナペニア（加齢による筋力低下）のほうが、高齢者のwellbeing（健康、幸福、福祉）への影響が大きく、サルコペニアとダイナペニアではかなり進み方が異なることがわかってきています。muscle quality（筋肉の質：横断面積あたりの筋力）の概念も重要です。

筋肉量低下は男性で年0.47%、女性で年0.37%です。75歳の高齢者になると、女性で年0.64-0.70%、男性で年0.80-0.98%の筋肉量低下を認めます。

一方、筋力低下の進み方はより速いです。75歳の高齢者では、男性で年3-4%、女性で年2.5-3%の筋力低下を認めます。つまり、高齢者の筋力低下は筋肉量低下より2-5倍速く、障害や死亡のリスクは筋力低下のほうがより高いです。

 狭義のサルコペニア（加齢による筋肉量低下のみ）で考えると、ダイナペニアは別の概念になります。一方、広義のサルコペニア（すべての原因による筋肉量低下、筋力低下、これらによる身体機能低下）には、ダイナペニアも含まれます。

研究上は、狭義のサルコペニアとダイナペニアで考えたほうが進めやすいと思いますが、リハ栄養の臨床上は広義のサルコペニア（すべての原因による筋力低下を含む）で考えたほうが、原因追究や対策立案が行いやすいと考えます。

Abstract

Changing demographics make it ever more important to understand the modifiable risk factors for disability and loss of independence with advancing age. For more than two decades there has been increasing interest in the role of sarcopenia, the age-related loss of muscle or lean mass, in curtailing active and healthy aging. There is now evidence to suggest that lack of strength, or dynapenia, is a more constant factor in compromised wellbeing in old age and it is apparent that the decline in muscle mass and the decline in strength can take quite different trajectories. This demands recognition of the concept of muscle quality; that is the force generating per capacity per unit cross-sectional area (CSA). An understanding of the impact of aging on skeletal muscle will require attention to both the changes in muscle size and the changes in muscle quality. The aim of this review is to present current knowledge of the decline in human muscle mass and strength with advancing age and the associated risk to health and survival and to review the underlying changes in muscle characteristics and the etiology of sarcopenia. Cross-sectional studies comparing young (18-45 years) and old (>65 years) samples show dramatic variation based on the technique used and population studied. The median of values of rate of loss reported across studies is 0.47% per year in men and 0.37% per year in women. Longitudinal studies show that in people aged 75 years, muscle mass is lost at a rate of 0.64-0.70% per year in women and 0.80-0.98% per year in men. Strength is lost more rapidly. Longitudinal studies show that at age 75 years, strength is lost at a rate of 3-4% per year in men and 2.5-3% per year in women. Studies that assessed changes in mass and strength in the same sample report a loss of strength 2-5 times faster than loss of mass. Loss of strength is a more consistent risk for disability and death than is loss of muscle mass.