Purpose: To assess the relationships between knee extension strengths and lower extremity functions in subjects with dementia and to predict lower extremity functions using knee extension strength.
Methods: Fifty-four nursing home residents with dementia were enrolled in the study. The strength of the knee extensor was measured using a hand-held dynamometer. To predict lower extremity functions, subjects were classified into two groups: those who could dress their lower body, toilet, transfer to bed/toilet/shower and walk independently, and those who required assistance. Knee extension strength was compared between the two groups.
Results: Logistic regression analysis showed that the strength of the knee extensor muscles was a significant predictor of the ability to dress the lower body (odds ratio, 109.90; 95% CI, 7.60-1589.49), toileting (odds ratio, 18.29; 95% CI, 2.41-138.84), transferring to bed/toilet/shower (odds ratio, 39.70; 95% CI, 4.51-349.08), and gait performance (odds ratio, 12.77; 95% CI, 2.30-70.77). The curve of the negative and positive predictive values indicated that a cutoff score of 0.8 Nm/kg would provide the best balance for dressing the lower body and toileting; 1.2 Nm/kg for transferring to bed/toilet/shower; and 0.6 Nm/kg for gait performance.
Conclusions: Knee extension strength was significantly related to the lower extremity functions in people with dementia. Moreover, threshold levels of strength existed that could predict lower extremity dysfunctions in people with dementia.