Validation of an automated up-timer for measurement of mobility in older adults.

Abstract

OBJECTIVE: To test the reliability, validity and utility of an "up-timer", an automated device to measure time spent standing and walking. DESIGN: Repeat measurement of mobility one week apart in a convenience sample. SETTING: Hostel and nursing homes in Melbourne. PARTICIPANTS: 26 hostel and 24 nursing home residents (aged 70-99 years) participated. They were mobile, with or without the use of walking aids or personal assistance. OUTCOME MEASURES: "Up-time" (measured with the up-timer); functional activity (measured with the Barthel Index, Functional Independence Measure, Timed Up & Go, and Human Activity Profile); and disability (measured by the Rapid Disability Rating Scale). RESULTS: The test-retest reliability of the up-timer was high (Pearson's r = 0.84; P < 0.001). Pearson's correlation between the up-timer results and results of functional and disability measures ranged from r = 0.47 to r = 0.55. The functional measures correlated more highly among themselves (r = 0.79 to r = 0.92). The performance-based Timed Up & Go test had moderate levels of correlation with both the up-timer and the functional measures. Use of the device was well accepted by both participants and staff. CONCLUSIONS: The up-timer is a practical, objective and reliable means of measuring mobility. The useful information it provides is different from, but overlaps with, that obtained from subjective observation or self report. It will complement existing subjective and performance-based measures of activity and mobility.