Reliability and validity of measurements of knee extension strength obtained from nursing home residents with dementia.

OBJECTIVE

To describe the reliability of strength measurement by hand-held dynamometer and to identify the prediction of gait and stand-up ability by the strength measurement in people with dementia.

DESIGN

Correlational study in which 60 persons with Alzheimer disease were enrolled. The strength of knee extensor was measured twice separated by a 3-min interval using a hand-held dynamometer. The presence or absence of impaired gait and sit-to-stand was also determined.

RESULTS

Intraclass correlation coefficient was 0.97. Bland-Altman plots showed the distribution of test-retest differences in the subjects with Mini-Mental State Examination score of 10 points or fewer, increased with isometric knee extensor strength. Logistic regression analysis showed strength of the knee extensor muscles to be a significant predictor of gait performance (odds ratio, 443.0; 95% confidence interval, 9.20-21325.7) and sit-to-stand performance (odds ratio, 47.32; 95% confidence interval, 3.31-675.8).

CONCLUSIONS

The strength measurement with a hand-held dynamometer was reliable in people with dementia. Furthermore, normalized knee extensor strength was indicated to be a significant predictor of gait and sit-to-stand performance. However, caution is needed when interpreting the result of strength measurement when it is carried out on subjects with a Mini-Mental State Examination score of 10 points or fewer and with a high strength level.