Article Text
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.
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Footnotes
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Funding BKC, PAG, GNH, EAHW and NO are supported by a Queensland Health Core Research Infrastructure grant and by NHMRC Program Grant funding (#569940). PAG is supported by a Heart Foundation of Australia (# PP 06B 2889). BKC is supported by an Australian Post-graduate Award. GNH is also supported by a NHMRC (#569861)/National Heart Foundation of Australia (PH 374 08B 3905) Postdoctoral Fellowship.
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Competing interests None.
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Ethics approval The study uses secondary data from two studies, each of which obtained ethical approval from relevant parties. AusDiab substudy – The University of Queensland, Ethics Committee of the International Diabetes Institute. NHANES (publically available data) had ethical approval from NHANES Institutional Review Board/NCHS Research Ethics Review Board.
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Provenance and peer review Not commissioned; externally peer reviewed.