TUESDAY, Jan. 4 (HealthDay News) -- Physical activity of knee osteoarthritis (OA) sufferers is more accurately recorded with accelerometers when 90 minutes of nonactivity is used as the nonwear threshold and 10 hours is used as the valid day threshold, according to a report published in the December issue of Arthritis Care & Research.
Jing Song, of the Northwestern University Feinberg School of Medicine in Chicago, and colleagues reviewed 3,536 days of accelerometer data for 519 people with knee OA. They assessed the influence of zero activity periods from 20 to 300 minutes and the effect of eight, 10, or 12 wear hours to signify a valid day of monitoring. The National Cancer Institute established a nonwear threshold of 60 minutes and a valid day of 10 hours for the general population.
The researchers found that a 90-minute nonwear threshold and a minimum of 10 wear hours constituted a valid day that provided data retention of 94 percent. They also found that mean daily activity minutes stabilized at 463 minutes per day and that expanding the nonwear threshold to 90 minutes had no effect on mean daily moderate to vigorous physical activity minutes.
"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," the authors write.
The authors disclosed funding from Merck Research Laboratories, Novartis Pharmaceuticals Corporation, GlaxoSmithKline, Pfizer Inc., and AstraZeneca; a co-author disclosed financial ties to Roche and Crescendo Biosciences.
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