Comparison of a Thigh-Worn Accelerometer Algorithm With Diary Estimates of Time in Bed and Time Asleep: The 1970 British Cohort Study
in Journal for the Measurement of Physical BehaviourBackground: Thigh-worn accelerometers have established reliability and validity for measurement of free-living physical activity-related behaviors. However, comparisons of methods for measuring sleep and time in bed using the thigh-worn accelerometer are rare. The authors compared the thigh-worn accelerometer algorithm that estimates time in bed with the output of a sleep diary (time in bed and time asleep). Methods: Participants (N = 5,498), from the 1970 British Cohort Study, wore an activPAL device on their thigh continuously for 7 days and completed a sleep diary. Bland–Altman plots and Pearson correlation coefficients were used to examine associations between the algorithm derived and diary time in bed and asleep. Results: The algorithm estimated acceptable levels of agreement with time in bed when compared with diary time in bed (mean bias of −11.4 min; limits of agreement −264.6 to 241.8). The algorithm-derived time in bed overestimated diary sleep time (mean bias of 55.2 min; limits of agreement −204.5 to 314.8 min). Algorithm and sleep diary are reasonably correlated (ρ = .48, 95% confidence interval [.45, .52] for women and ρ = .51, 95% confidence interval [.47, .55] for men) and provide broadly comparable estimates of time in bed but not for sleep time. Conclusions: The algorithm showed acceptable estimates of time in bed compared with diary at the group level. However, about half of the participants were outside of the ±30 min difference of a clinically relevant limit at an individual level.
Hamer and Stamatakis are joint senior authors. Inan-Eroglu, Huang, and Stamatakis are with the Charles Perkins Centre, School of Health Sciences, Faculty of Medicine and Health, The University of Sydney, NSW, Australia. Shepherd is with the Prevention Research Collaboration, School of Public Health, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia. Pearson is with the School of Sport Exercise Health Sciences, Loughborough University, Loughborough, United Kingdom. Koster is with the Department of Social Medicine, CAPHRI Care and Public Health Research School, Maastricht University, Maastricht, The Netherlands. Palm is with the School of Occupational and Environmental Medicine, Department of Medical Sciences, Uppsala University, Uppsala, Sweden. Cistulli is with the Sleep Research Group, Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia. Hamer is with the Division Surgery Interventional Sciences, Faculty of Medical Sciences, Institute Sport Exercise Health, University College London, London, United Kingdom.
Supplementary Materials
- Supplementary Figure S1 (PDF 784 KB)
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- Supplementary Material 1 (PDF 392 KB)
- Supplementary Table S1 (PDF 415 KB)
- Supplementary Table S2 (PDF 396 KB)
- Supplementary Table S3 (PDF 326 KB)
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- Supplementary Table S5 (PDF 334 KB)
- Supplementary Table S6 (PDF 219 KB)
- Supplementary Table S7 (PDF 332 KB)
- Supplementary Table S8 (PDF 500 KB)
- Supplementary Table S9 (PDF 501 KB)
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