1 National Food Institute, Technical University of Denmark2 Division of Nutrition, National Food Institute, Technical University of Denmark3 University of Copenhagen4 Children's Hospital of Eastern Ontario Research Institut
Accelerometers could potentially be used to assess physical activity and sleep using the same monitor; however, two different positions are typically used for the assessment of physical activity and sleep (waist and wrist, respectively). The aim of this study is to evaluate the concordance between wrist- and waist-worn Actigraphs for sleep scoring using existing algorithms developed for placement on the wrist. Sixty-two Danish children aged 10.3 ± 0.6 years (mean ± standard deviation) wore an accelerometer (Actigraph GT3X+ Tri-Axis Accelerometer Monitor) on the right hip and on the non-dominant wrist for a continuous 7 days and 8 nights. The minute-by-minute sleep-wake agreement was evaluated and the concordance among sleep indicators was assessed using one-way ANOVA, Bland-Altman plots and Pearson correlations. The sensitivity, specificity and accuracy were 98.8-99.7, 29.8-46.9 and 86.6-88.9%, respectively. Total sleep time and sleep efficiency were higher when assessed from the waist compared to the wrist measurement site (73.8 min, P <0.001; 12.6%, P <0.001, respectively). In conclusion, the waist-worn and wrist-worn Actigraph monitors cannot be used interchangeably for the measurement of sleep indicators in children using the present algorithms. However, the waist-worn Actigraph monitor can provide a proxy measure of total sleep time for ranking purposes in epidemiologic studies.
Sleep and Biological Rhythm, 2012, Vol 10, Issue 4, p. 328-335