地域在宅高齢者における骨格筋量・骨格筋力と 開口力との関連性

【目的】要介護高齢者の一要因である骨格筋量の低下や筋力低下は，嚥下関連筋にも影響を及ぼし，摂食嚥下機能を低下させることが疑われる．本研究では，地域在宅高齢者の骨格筋量・骨格筋力と，口腔機能・摂食嚥下機能との関連性を明らかにすることを目的として，調査を実施した．
【対象と方法】対象は，65歳以上の地域在宅高齢者24名（男性3名，女性21名，平均年齢77.0±5.0 歳）とした．骨格筋量は骨格筋指数（以下，SMI）を，骨格筋力は握力を評価項目として用いた．口腔機能・摂食嚥下機能は開口力・オーラルディアドコキネシス（以下，OD）/ タ/ と/ カ/・RSST・MWST を測定し，骨格筋量と骨格筋力との関連性を検討した．各項目の相関関係をスピアマンの順位相関係数にて解析した．その後，有意な関連のあった項目に年齢，性別を加え，重回帰分析（ステップワイズ法）を行った．さらに，握力の値から，筋力健常群と筋力低下群（男性＜ 26 kg，女性＜ 18 kg）の2群に分類し，口腔機能・摂食嚥下機能の各項目について比較した．2群間比較には，マン・ホイットニーのU 検定を用いて統計解析した．
【結果と考察】SMI と開口力，握力と開口力・OD / タ/ に有意な相関関係が認められた（r＝0.578，p＝0.003；r＝0.640，p＝0.001；r＝0.447，p＝0.029）．重回帰分析の結果，開口力に影響を与える因子としてSMI が挙げられた．また，筋力低下群の開口力は，筋力健常群よりも有意に低い値を示した（p＝0.011）．全身の骨格筋量，骨格筋力の低下は，開口力やOD / タ/ の低下に関連する可能性が考えられた．
【結論】地域在宅高齢者の骨格筋量と骨格筋力は，開口力や舌運動機能に関連する可能性が示唆された．

Skeletal muscle mass decreasing and muscle weakness can cause long-term care needs for elderly people. The relationship between skeletal muscle status and muscles relevant to oral function has been little reported. Therefore, the aim of the present study was to survey skeletal muscle status, oral function, and the relationship between the two in community-dwelling elderly people.
Twenty-four community-dwelling elderly from two elderly associations in N city, T prefecture enrolled in the present survey (3 males, 21 females; mean age, 77.0±5.0 years). Skeletal muscle index (SMI) was used to assess skeletal muscle mass, grasping power to assess skeletal muscle strength. Oral function was evaluated in terms of jaw-opening force, diadochokinesis, the repetitive saliva swallowing test (RSST), and the modified water swallowing test (MWST). Correlations between parameters were analyzed using Spearman’s correlation coefficient. Consequently stepwise regression analysis was performed with jaw-opening force as objective variable and SMI, grasping force, age and sex as explanatory variables.
The subjects were divided into two groups according to standards for grasping force: healthy and muscle weakness (male: ＜26 kgw; female: ＜18 kgw). Parameters were statistically compared between the two groups using the Mann-Whitney U test.
There were statistical relationships between SMI and jaw-opening force (r＝0.578, p＝0.003), grasping force and jaw-opening force (r＝0.640, p＝0.001), grasping force and the number of diadochokinetic movement of /ta/ (r＝0.447, p＝0.029). As a result of stepwise regression analysis, SMI was a factor that affects jaw-opening force.
In the muscle weakness group, jaw-opening force was less than the value in the healthy group ( p＝ 0.011). It is reasonable that an overall decrease in muscle mass would evoke decreases in muscle strength in both the extremities and the jaw-opening muscles.
We confirmed significant relationships between skeletal muscle mass, skeletal muscle strength, and oral function (i.e., jaw-opening force and tongue skilled movement) in Japanese community-dwelling elderly.