Actigraphically recorded motor activity and immobility across sleep cycles and stages in healthy male subjects

Abstract

The aim of this study was to compare the extent to which activity and immobility measures are related to sleep stages and sleep cycles in order to improve the informative value of actigraphic assessment of sleep. We therefore performed simultaneous ambulatory polysomnography and wrist-activity monitoring (AM) in 14 healthy male subjects without sleep complaints. In this context, a simple method for transforming raw motor activity data into a time-series reflecting onset and duration of activity and immobility clusters is introduced. Our results demonstrate that nocturnal AM measures were significantly affected by sleep stage. Low activity levels and particularly prolonged episodes of uninterrupted immobility were associated with increasing sleep depth. On the other hand, high activity levels and prolonged episodes of activity were related to intermittent wakefulness during sleep. Our results suggest that measures reflecting the occurrence and duration of activity and immobility clusters provide a better approach in studying the relationship between activity/immobility and sleep stages. Except for the duration of uninterrupted immobility episodes, which showed a significant decrease in the fourth cycle, none of the AM measures showed a significant cycle-to-cycle variation. Consequently, mean nocturnal motor activity measures provide an accurate reflection of the total sleep period. However, none of the AM-derived measures seems useful in evaluating the cycle structure during sleep.

Spontaneous movements during sleep in children: Temporal organization and changes with age

“…have been found to follow phasic REM events such as eye movements and PGO waves (Okada, Iwase, Mano, Sugiyama, & Watanabe, 1991). However, it is important to note that, despite motor atonia, rates of body movements are found to be highest during REM sleep, decline during Stage 2, and are lowest in Stages 3 and 4 (Horne et al, 1995;Middelkoop, Van Hilten, Kramer, & Kamphuisen, 1993;Naitoh, Muzet, Johnson, & Moses, 1973;Wilde-Frenz & Schulz, 1983). Kohyama, Shimohira, and Iwakawa (1996) recorded gross movements in duration during Ͼ 2 s REM sleep in children between 34 weeks conceptional age and 7 years of age.…”

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