Identifying sedentary time using automated estimates of accelerometer wear time. Issue 6 (18th April 2011)

• Record Type: Journal Article
• Authors: Winkler, Elisabeth A H; Gardiner, Paul A; Clark, Bronwyn K; Matthews, Charles E; Owen, Neville; Healy, Genevieve N
• Is Part Of: British journal of sports medicine. Volume 46:Issue 6(2012)
• Page Start: 436
• Page End: 442
• Publication Date: 2011-04-18
• Subjects: Sports medicine -- Periodicals; 617.1027
• DOI: 10.1136/bjsm.2010.079699
• Languages: English
• ISSNs: 0306-3674

Abstract

Abstract : Purpose: The authors evaluated the accuracy of three automated accelerometer wear-time estimation algorithms against self-report. Direct effects on sedentary time (<100 cpm) and indirect effects on moderate-to-vigorous physical activity (MVPA, ≥1952 cpm) time were examined. Methods: A subsample from the 2004/2005 Australian Diabetes, Obesity and Lifestyle Study (n=148) completed activity logs and wore accelerometers for a total of 987 days. A published algorithm that allows movement within non-wear periods (Algorithm 1) was compared with one that allows less movement (Algorithm 2) or no movement (Algorithm 3). Implications for population estimates were examined using 2003/2004 US National Health and Nutrition Examination Survey data. Results: Mean difference per day between the criterion and estimated wear time was negligible for all three algorithms (≤11 min), but 95% limits of agreement (LOA) were wide (±≥2 h). Respectively, the algorithms (1, 2 and 3) misclassified sedentary time as non-wear on 31.9%, 19.4% and 18% of days and misclassified non-wear time as sedentary on 42.8%, 43.7% and 51.3% of days. Use of Algorithm 2 (compared with Algorithm 1) affected population estimates of sedentary time (higher by 20 min/day) but not MVPA time. Agreement between Algorithms 1 and 2 was good for MVPA time (mean difference −0.08, LOA: −2.08, 1.91 min), but not for wear time or sedentary time. Conclusion: Accelerometer wear time can be estimated accurately on average; however, misclassification can be substantial for individuals. Algorithm choice affects estimates of sedentary time. Allowing very limited movement within non-wear periods can improve accuracy.