Reliability of physical performance measures in nursing home residents with Alzheimer's disease

Background. Investigation of the effects of exercise on frail, institutionalized individuals with dementia has been impeded by concerns about the reliability of physical performance measures when used in this population. Methods. The physical performance of 33 institutionalized subjects with Alzheimer's disease was measured during both the morning and afternoon of day 1 by rater 1 and during both the morning and afternoon of day 2, one week later, by rater 1 and rater 2. Intraclass correlation coefficients (ICCs) were calculated to examine the inter- and intrarater reliability of ''sit to stand,'' ''25-foot walk,'' and ''the distance walked in 6 minutes'' and walking speed over 25 feet and for 6 minutes. An analysis of variance was performed to determine the components of variance for each test. Results. ICCs for ''distance walked in 6 minutes'' ranged from .80 to .99 with 77% of the variance explained by inter-subject differences. The ICCs for ''time to walk 25 feet'' ranged from .57 to .97 with 25% of the variance explained by inter-subject differences. In contrast, the ''sit to stand'' measure produced ICCs ranged from -.07 to .85 with only 7% of the variance explained by inter-subject differences in the impaired population. Conclusion. Our results support the contention that some physical performance measures can be used to test individuals in the later stages of Alzheimer's disease given appropriate modification. Although subjects with Alzheimer's disease may have difficulty following commands and/or require physical assistance, the does not prohibit the reliable assessment of physical performance if measurements are made over longer (6-minute walk) rather than shorter periods (25-foot walk).