Assessing physical activity in persons with knee osteoarthritis using accelerometers: Data from the osteoarthritis initiative
Article first published online: 30 NOV 2010
Copyright © 2010 by the American College of Rheumatology
Arthritis Care & Research
Volume 62, Issue 12, pages 1724–1732, December 2010
How to Cite
Song, J., Semanik, P., Sharma, L., Chang, R. W., Hochberg, M. C., Mysiw, W. J., Bathon, J. M., Eaton, C. B., Jackson, R., Kwoh, C. K., Nevitt, M. and Dunlop, D. D. (2010), Assessing physical activity in persons with knee osteoarthritis using accelerometers: Data from the osteoarthritis initiative. Arthritis Care Res, 62: 1724–1732. doi: 10.1002/acr.20305
- Issue published online: 30 NOV 2010
- Article first published online: 30 NOV 2010
- Accepted manuscript online: 30 AUG 2010 10:22AM EST
- Manuscript Accepted: 20 JUL 2010
- Manuscript Received: 30 MAR 2010
- National Institute of Arthritis and Musculoskeletal and Skin Diseases. Grant Numbers: R01-AR054155, R21-AR059412, P60-AR48098, R01-AR055287
- The Osteoarthritis Initiative is a public-private partnership comprised of 5 contracts funded by the NIH, a branch of the Department of Health and Human Services. Grant Numbers: N01-AR-2-2258, N01-AR-2-2259, N01-AR-2-2260, N01-AR-2-2261, N01-AR-2-2262
- Osteoarthritis Initiative Study Investigators
- Merck Research Laboratories
- Novartis Pharmaceuticals Corporation
- Pfizer Inc.
- Osteoarthritis Initiative is managed by the Foundation for the NIH
- The Beverage Institute
Physical activity measured by accelerometers requires basic assumptions to translate the output into meaningful measures. We used accelerometer data from the Osteoarthritis Initiative to investigate in the context of knee osteoarthritis (OA) the following data processing assumptions derived from the general US adult population: nonwear (a period the monitor was removed), based on zero activity exceeding 60 minutes; and a valid day of monitoring, based on wear time evidence exceeding 10 hours.
We examined the influence of nonwear thresholds ranging from 20 to 300 minutes of zero activity on mean daily activity minutes (counts >0), mean daily activity counts, and mean daily moderate to vigorous physical activity minutes. The effect of selecting minimums of 8, 10, or 12 wear hours to signify a valid day of monitoring on data retention was examined.
Our sample of 3,536 days of accelerometer data from 519 persons with knee OA showed that mean daily activity minutes increased with the nonwear threshold until stabilizing at 463 minutes per day, corresponding to the 90-minute nonwear threshold. Similar patterns were observed for mean daily activity counts. Varying the nonwear threshold had no effect on mean daily moderate to vigorous physical activity minutes. Choosing the 90-minute nonwear threshold and a minimum of 10 wear hours to constitute a valid day provided 94% data retention.
Data supported applying the 90-minute nonwear threshold to the knee OA population instead of the 60-minute threshold for the general population, while retaining the 10-hour valid day threshold.