Day‐to‐day variability and year‐to‐year reproducibility of accelerometer‐measured free‐living sit‐to‐stand transitions volume and intensity among community‐dwelling older adults

Abstract

(1) Background: The purpose of this study was to evaluate the day‐to‐day variability and year‐to‐year reproducibility of an accelerometer‐based algorithm for sit‐to‐stand (STS) transitions in a free‐living environment among community‐dwelling older adults. (2) Methods: Free‐living thigh‐worn accelerometry was recorded for three to seven days in 86 (women n = 55) community-dwelling older adults, on two occasions separated by one year, to evaluate the long‐term consistency of free‐living behavior. (3) Results: Year‐to‐year intraclass correlation coefficients (ICC) for the number of STS transitions were 0.79 (95% confidence interval, 0.70–0.86, p < 0.001), for mean angular velocity—0.81 (95% ci, 0.72–0.87, p < 0.001), and maximal angular velocity—0.73 (95% ci, 0.61–0.82, p < 0.001), respectively. Day‐to‐day ICCs were 0.63–0.72 for number of STS transitions (95% ci, 0.49–0.81, p < 0.001) and for mean angular velocity—0.75–0.80 (95% ci, 0.64–0.87, p < 0.001). Minimum detectable change (MDC) was 20.1 transitions/day for volume, 9.7°/s for mean intensity, and 31.7°/s for maximal intensity. (4) Conclusions: The volume and intensity of STS transitions monitored by a thigh‐worn accelerometer and a sit‐to‐stand transitions algorithm are reproducible from day to day and year to year. The accelerometer can be used to reliably study STS transitions in free‐living environments, which could add value to identifying individuals at increased risk for functional disability.