Measuring Physical Activity in Older Adults Using MotionWatch 8 Actigraphy: How Many Days are Needed?

in Journal of Aging and Physical Activity
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Evidence suggests sleep and physical activity (PA) are associated with each other and dementia risk. Thus, identifying reliable methods to quantify sleep and PA concurrently in older adults is important. The MotionWatch 8© (MW8) wrist-worn actigraph provides reliable estimates of sleep quality via 14 days of measurement; however, the number of days needed to monitor PA by MW8 for reliable estimates is unknown. Thus, we investigated the number of days of MW8 wear required to assess PA in older adults. Ninety-five adults aged > 55 years wore MW8 for ≥ 14 days. Spearman-Brown analyses indicated the number of monitoring days needed for an ICC = 0.95 was 6–7 days for sedentary activity, 9–10 days for light activity, and 7–8 days for moderate-to-vigorous PA. These results indicate 14 days of MW8 monitoring provides reliable estimates for both sleep and PA. Thus, MW8 is ideal for future investigations requiring concurrent measures of both sleep quality and PA.

Falck and Landry are with the Aging, Mobility, and Cognitive Neuroscience Laboratory, Department of Physical Therapy, University of British Columbia, Vancouver, British Columbia, Canada; and the Djavad Mowafaghian Centre for Brain Health, Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, British Columbia, Canada. Brazendale is with the Department of Exercise Science, University of South Carolina, Columbia, South Carolina, USA. Liu-Ambrose is with the Aging, Mobility, and Cognitive Neuroscience Laboratory, Department of Physical Therapy, University of British Columbia, Vancouver, British Columbia, Canada; Djavad Mowafaghian Centre for Brain Health, Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, British Columbia, Canada; and Centre for Hip Health, Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, British Columbia, Canada. *Shared first authorship.

Address correspondence to Teresa Liu-Ambrose at teresa.ambrose@ubc.ca.
Journal of Aging and Physical Activity