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Erschienen in:
01.09.2012
Agreement in Regard to Total Sleep Time During a Nap Obtained Via a Sleep Polygraph and Accelerometer: A Comparison of Different Sensitivity Thresholds of the Accelerometer
Erschienen in: International Journal of Behavioral Medicine | Ausgabe 3/2012
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Background
Appropriate sensitivity threshold of accelerometer to measure total sleep time during nap is not established.
Purpose
Actigraphy-derived total sleep times during naps were calculated using three different sensitivity threshold values and compared with polysomnography.
Method
The mean age of the 60 subjects (53 men and 7 women) was 22.8, ranging from 22 to 27 years. Determination of the sleep stage by the polygraph and the sleep/wake judgment by the accelerometer obeyed the sleep/wake judgment, and the accelerometer was monitored under different sensitivity threshold settings. The study was carried out during one afternoon with a 3-h nap opportunity. Kappa statistics, correlations, and several indices of accuracy were compared using statistical methods.
Results
The mean total sleep times during a nap set for 180 min were 160.4, 151.8, and 140.5 min, respectively, as judged under the low-sensitive, middle-sensitive, high-sensitive settings of an accelerometer worn on the non-dominant wrist. The corresponding mean total sleep time as calculated using a sleep polygraph was 133.0 min. Sleep/wake judgment by three levels of threshold values for the accelerometer showed that high-sensitive threshold showed relatively high specificity (0.452) compared with specificities by the low-sensitive threshold (0.249) or by the middle-sensitive threshold (0.358). The concordance correlation coefficients and 95% confidence intervals (in parenthesis) between the total sleep time judged by polygraph and low-sensitive, middle-sensitive, or high-sensitive accelerometer were 0.40 (0.26–0.51), 0.53 (0.38–0.65), and 0.64 (0.49–0.75), respectively. The Bland–Altman plot of the measurements showed higher agreement between the total sleep time by polygraph and by the accelerometer using the high-sensitive threshold.
Conclusions
From the result obtained in this study, the high-sensitive accelerometer showed the strongest agreement of total sleep time and sleep/wake judgment with the calculated value using the sleep polygraph.