サルコペニアと関節リウマチでの筋力低下の比較

今日はサルコペニア（加齢に伴う狭義、原発性のもの）と関節リウマチ（広義でのサルコペニアに該当）での筋力低下の比較をした系統的レビュー論文を紹介します。

Beenakker,K.G.M.,etal. Patterns of muscle strength loss with age in the general population and patients with a chronic inflammatory state. Ageing Res. Rev.(2010), doi:10.1016/j.arr.2010.05.005

結果としては、健常者では加齢に伴い徐々に握力が低下します。 25歳と95歳で比較すると、男性の平均握力は45.5kgから23.2kgに、女性の平均握力は27.1kgから12.8kgに低下します。50歳以降で握力低下の速度が速くなり、1年あたり0.37kg低下します。

75歳時点で男性の平均握力は31.8(30.5;33.2)kg、女性の平均握力は19.1(17.9;20.3)kgです。サルコペニアの診断基準の目安が男性30kg、女性20kgですから、75～80歳以上になれば、半数はサルコペニアの可能性があるといえます。

一方、関節リウマチでは35歳から65歳の間で、握力の変化はほとんどありませんでした。この間、男性で平均20kg、女性で平均15kgです。ただし、罹病期間が長くなると握力は低下傾向にあります。

関節リウマチでの握力低下は、悪液質に伴う二次性サルコペニアの影響もありますが、手指の変形、こわばりによるものもあります。そのため、すべてが二次性サルコペニアによる握力低下とは言えませんので、留意が必要です。

ただ、原発性サルコペニアと二次性サルコペニアによる握力低下の違いを比較検討したという点では、意味のある論文だと考えます。

Abstract
BACKGROUND: There is growing recognition of the serious consequences of sarcopenia on the functionality and autonomy in old age. Recently, the age-related changes in several inflammatory mediators have been implicated in the pathogenesis of sarcopenia. The purposes of this systematic review were two-fold: (1) to describe the patterns of muscle strength loss with age in the general population, and (2) to quantify the loss of muscle strength in rheumatoid arthritis as representative for an underlying inflammatory state. Handgrip strength was used as a proxy for overall muscle strength.

RESULTS: Results from 114 studies (involving 90,520 subjects) and 71 studies (involving 10,529 subjects) were combined in a meta-analysis for the general and rheumatoid arthritis population respectively and standardized at an equal sex distribution. For the general population we showed that between the ages of 25 and 95 years mean handgrip strength declined from 45.5kg to 23.2kg for males and from 27.1kg to 12.8kg for females. We noted a steeper handgrip strength decline after 50 years of age (rate of 0.37kg/year). In the rheumatoid arthritis population handgrip strength did not change between the ages of 35 to 65 years. Rheumatoid arthritis disease duration was inversely associated with handgrip strength.

CONCLUSIONS: This meta-analysis shows distinct patterns of age-related decrease of handgrip strength in the general population. Handgrip strength is strongly associated with the presence and duration of an inflammatory state as rheumatoid arthritis. The putative link between age-related inflammation and sarcopenia mandates further study as it represents a potential target for intervention to maintain functional independence in old age.