頸部筋肉量と脳容量・認知機能

健常高齢男性における頸部筋肉横断面積と脳容積と認知機能の関連をみた論文を紹介します。

Kilgour AH, Ferguson KJ, Gray CD, Deary IJ, Wardlaw JM, Maclullich AM, Starr JM. Neck muscle cross-sectional area, brain volume and cognition in healthy older men; a cohort study. BMC Geriatr. 2013 Feb 28;13(1):20. [Epub ahead of print]

正常加齢ではサルコペニアと年齢による認知機能低下が大きな問題です。先行研究で筋肉機能、認知機能、脳構造に正の関係があることは示されていますが、筋肉量を考慮した研究は少数です。そのため、頸部筋肉量と脳容積と認知機能の関連を調査しました。

対象は健常高齢者51人（平均年齢73.8歳）です。頸部筋肉量はMRIで測定しました。認知機能として記憶（視覚、言語）、遂行機能、推測されるもとの認知機能を評価し、脳容積はMRIで脳全体、海馬、小脳を評価しました。

結果ですが、頸部筋肉横断面積が大きいと脳全体の萎縮が有意に少なかったです。頸部筋肉横断面積は他の脳容積や認知機能とは有意な関連を認めませんでした。頸部筋肉横断面積が小さいと推測されるもとの認知機能が有意に高かったです。

サルコペニアと認知機能に関連があるかどうかは、今回の研究だけでは不明ですね。頭が重いほど頸部への負担が大きく頸部筋肉量も増えるでしょうし。栄養状態が著しく悪いと両者に影響を与えるでしょうし。縦断研究で交絡因子の十分な検討が必要だと思います。

Abstract

BACKGROUND:

Two important consequences of the normal ageing process are sarcopenia (the age-related loss of muscle mass and function) and age-related cognitive decline. Existing data support positive relationships between muscle function, cognition and brain structure. However, studies investigating these relationships at older ages are lacking and rarely include a measure of muscle size. Here we test whether neck muscle size is positively associated with cognition and brain structure in older men.

METHODS:

We studied 51 healthy older men with mean age 73.8 (sd 1.5) years. Neck muscle cross-sectional area (CSA) was measured from T1-weighted MR-brain scans using a validated technique. We measured multiple cognitive domains including verbal and visuospatial memory, executive functioning and estimated prior cognitive ability. Whole brain, ventricular, hippocampal and cerebellar volumes were measured with MRI. General linear models (ANCOVA) were performed.

RESULTS:

Larger neck muscle CSA was associated with less whole brain atrophy (t = 2.86, p = 0.01, partial eta squared 17%). Neck muscle CSA was not associated with other neuroimaging variables or current cognitive ability. Smaller neck muscle CSA was unexpectedly associated with higher prior cognition (t = -2.12, p < 0.05, partial eta squared 10%).

CONCLUSIONS:

In healthy older men, preservation of whole brain volume (i.e. less atrophy) is associated with larger muscle size. Longitudinal ageing studies are now required to investigate these relationships further.