Temporal association between transient arousals and limb movement during sleep

Abstract

Introduction: Actigraphy has been increasingly used for remotely assessing sleep quality in children with symptomatic sleep apnoea. However, actigraphy falsely identifies periods of movement during sleep as wakefulness, resulting in poor specificity for sleep. Given that transient arousals during sleep may manifest as body/limb movements, we hypothesised that arousal events may partly explain these falsely detected wake epochs; and conversely, that limb movement may predict arousal events. Method: Thirty otherwise healthy children (5-16 years, 21 male, AHI 0-16.9) with suspected sleep apnoea were studied using full polysomnography and raw tri-axial accelerometry measured at the wrist, synchronised to within 0.1 s of the polysomnogram. Movement segments were automatically detected using a custom routine. The duration and proportion of arousal events that were associated with movement were then analysed. Results: 67.5% of arousals had an associated wrist movement. These arousal events were longer than events without movement (12.2 s vs. 7.9 s, p < 0.01). 17.5% of movements during sleep occurred during an arousal event. These movements were longer than other movements during sleep (9.9 s vs. 2.7 s, p < 0.01), but similar to those during wake. (Figure Presented) Discussion: Arousal-related movements likely contribute to a high activity count in the corresponding epoch, which may incorrectly be scored as wakefulness using conventional actigraphy. Nonetheless, these epochs are being correctly identified as sleep disturbance. We also note that sleep movements are significantly shorter than wake and arousalrelated movements. As such, identifying these short movements as sleep would improve the accuracy of actigraphy-based sleep classification. Finally, although actigraphy-based measurements cannot reliably predict all arousal events, actigraphy can likely identify longer events that may have the greatest impact on sleep quality.L720719542015-11-20 <br />