Original article
Validation of a Body-Worn Accelerometer to Measure Activity Patterns in Octogenarians

https://doi.org/10.1016/j.apmr.2014.01.013Get rights and content

Abstract

Objective

To determine the validity of a triaxial body-worn accelerometer for detection of gait and postures in people aged >80 years.

Design

Participants performed a range of activities (sitting, lying, walking, standing) in both a controlled and a home setting while wearing the accelerometer. Activities in the controlled setting were performed in a scripted sequence. Activities in the home setting were performed in an unscripted manner. Analyzed accelerometer data were compared against video observation as the reference measure.

Setting

Independent-living and long-term-care retirement village.

Participants

Older people (N=22; mean age ± SD, 88.1±5y) residing in long-term-care and independent-living retirement facilities.

Interventions

Not applicable.

Main Outcome Measures

The level of agreement between video observation and the accelerometer for the total duration of each activity, and second-by-second correspondence between video observation and the accelerometer for each activity.

Results

The median absolute percentage errors between video observation and the accelerometer were <1% for locomotion and lying. The absolute percentage errors were higher for sitting (median, −22.3%; interquartile range [IQR], −62.8% to 10.7%) and standing (median, 24.7%; IQR, −7.3% to 39.6%). A second-by-second analysis between video observation and the accelerometer found an overall agreement of ≥85% for all activities except standing (median, 56.1%; IQR, 34.8%–81.2%).

Conclusions

This single-device accelerometer provides a valid measure of lying and locomotion in people aged >80 years. There is an error of approximately 25% when discriminating sitting from standing postures, which needs to be taken into account when monitoring longer-term habitual activity in this age group.

Section snippets

Participants

Twenty-two people (mean age ± SD, 88.1±5y) from 2 retirement villages volunteered to participate (table 1). Eligible participants were aged ≥80 years, were living in either independent or long-term care (nursing home) facilities at the retirement village, and were able to transfer and walk independently with or without a walking aid. Ethical approval for the study was granted by the University of Auckland Ethics Committee. All participants gave written informed consent before commencement.

Procedure

The

Results

A total of 251.30 minutes of activity were analyzed from 22 participants (table 2). One participant did not complete the scripted activities, and 4 participants did not perform the lying component of the scripted activities.

Bland-Altman plots with mean differences and limits of agreement for each activity are shown in figure 1. When expressed as an absolute percentage error, the median absolute percentage error for each activity was as follows: sitting, −22.3% (interquartile range [IQR], −62.8%

Discussion

This study assessed the validity of the DynaPort MoveMonitor system for detection of gait and postures in older people in both a controlled setting and a home setting. There was close agreement between video observation and the accelerometer for both locomotion and lying, with an absolute percentage error of <1% for these activities. Since the slow gait speed of older people can result in misclassification of walking as standing, or the underestimation of step counts when using pedometers or

Conclusions

The DynaPort MoveMonitor provides a precise measure of lying and locomotion in people older than 80 years including the frail elderly, although there is an error of approximately 25% when discriminating sitting from standing postures. This error in discrimination needs to be considered when monitoring long-term habitual activity in this age group.

Suppliers

  • a.

    McRoberts BV, Raamweg 43, 2596 HN, The Hague, The Netherlands.

  • b.

    Sony Handycam (HDR-SR5); Sony Corp, 1-7-1 Konan, Minato-ku, Tokyo 108-0075, Japan.

  • c.

    Microsoft Corp, One Microsoft Way, Redmond, WA 98052.

  • d.

    The MathWorks, Inc, 3 Apple Hill Dr, Natick, MA 01760-2098.

  • e.

    SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.

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    Supported jointly by the research and development program of the Korea Ministry of Knowledge and Economy and Korea Evaluation Institute of Industrial Technology (grant no. KI001836: Development of Mediated Interface Technology for Human Robot Interaction) and by the New Zealand Ministry for Science and Innovation (grant no. 13635).

    No commercial party having a direct financial interest in the results of the research supporting this article has conferred or will confer a benefit on the authors or on any organization with which the authors are associated.

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