Assessing physical activity in persons with knee osteoarthritis using accelerometers: data from the osteoarthritis initiative.

Jing Song*, Pamela Semanik, Leena Sharma, Rowland W. Chang, Marc C. Hochberg, W. Jerry Mysiw, Joan M. Bathon, Charles B. Eaton, Rebecca Jackson, C. Kent Kwoh, Michael Nevitt, Dorothy D. Dunlop

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

64 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)1724-1732
Number of pages9
JournalArthritis Care and Research
Volume62
Issue number12
DOIs
StatePublished - Dec 2010

ASJC Scopus subject areas

  • Rheumatology

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