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Actigraphy
Kushang V. Patel, PhD, MPHUniversity of Washington, Seattle
IMMPACT XVIIApril 17, 2014
Objective
• To provide an overview of accelerometry as an objective measure of physical activity for use in analgesic clinical trials in chronic musculoskeletal pain populations
Accelerometers
• Small, lightweight, portable, noninvasive, and nonintrusive devices that record motion in 1, 2, or 3 planes
• Measures frequency, duration, and intensity of physical activity
Compliance with Physical Activity Guidelines among Adults in the US, NHANES 2005-06
Men Women0
10
20
30
40
50
60
70
Self-reportAccelerometer%
Tucker JM, et al. Am J Prev Med 2011
Compliance with Physical Activity Guidelines among Adults in the US, NHANES 2005-06
Men Women0
10
20
30
40
50
60
70
Self-reportAccelerometer%
Tucker JM, et al. Am J Prev Med 2011
Microelectromechanical System
Chen K, et al. Med Sci Sports Exerc 2012
Accelerometer “Counts”• Dimensionless units that are specific to each
make and model of monitor– Cannot be compared across devices
• Measure the frequency and intensity of acceleration in a given plane (eg, vertical displacement)
• Time stamped• Accumulated over a discrete, user-defined time-
sampling interval (“epochs”; 1, 15, 30 seconds)• Shorter epochs provide greater detail, but
consume more memory and reduce battery life
Validity of Accelerometry• Validity studies have yielded moderate-to-
strong correlations between accelerometer counts and oxygen consumption (VO2max), PAEE, or MET – r = 0.45 to 0.93 in adults– r = 0.53 to 0.92 in children
• Wide range in correlation is due, to a large extent, to the type of measurement protocol– Uniaxial vs triaxial– Improvements in signal filtration, use of raw data
• ICCs>0.95 for inter- and intra-model reliabilityButte NF, et al. Med Sci Sports Exerc 2012
Chen K, et al. Med Sci Sports Exerc 2012
Signal Filtering Effect
Chen K, et al. Med Sci Sports Exerc 2012
Monitoring time
• Up to 30 days of monitoring, but memory and wireless capacities are improving
• Valid day = at least 10 hours or 60% of waking hours are recommended
• Sampling 3 or more days, including weekdays and weekend days are recommended
Device Placement
• Data from all locations provide similar levels of accuracy, although the hip provides the best single location to record data for activity detection
Cleland I, et al. Sensors 2013
Activities tested: walking, running on treadmill, sitting, lying, standing and walking up and down stairs
Activity counts by age (N=611)<60 years60-67 year68-74 years>=75 years
Schrack JA, et al. J Gerontol A Biol Sci Med Sci 2014
Chronic Widespread Pain and Objectively Measured Physical Activity in Adults: NHANES 2003-2004
Dansie EJ, et al. J Pain 2014
McLoughlin MJ, et al. Med Sci Sports Exerc 2013
Accelerometer Counts During a 6-minute Walk Test in Older Adults (N=319)
Van Domelen DR, et al. J Phys Act Health 2014
r = 0.80
Accelerometer Counts During a 6-minute Walk Test in Older Adults (N=319)
Vertical axisr = 0.80
AP axisr = 0.55
ML axisr = 0.16
Van Domelen DR, et al. J Phys Act Health 2014
Total Daily Physical Activity and Incident Disability in Basic ADLs (N=718)
Shah RC, et al. BMC Geriatr 2012
Hernandez-Hernandez et al. Rheumatol 2014
r = -0.46
“Movelets”
Bai J, et al. Electron J Stat 2013
Considerations Pros • Objective, continuous monitoring• Free-living• High density data, detect lighter intensity activities• PassiveCons• Costs ($100-$300/device)• Lack context• Underestimates some activities (bicycling, strength training)• Lack of industry standards, device-specific parameters• Data processing & analysis expertise
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