A Prospective Video-Polysomnographic Analysis of Movements during Physiological Sleep in 100 Healthy Sleepers

Study objectives: Video-polysomnography (v-PSG) is the gold standard for the diagnosis of sleep disorders. Quantitative assessment of type and distribution of physiological movements during sleep for the differentiation between physiological and pathological motor activity is lacking. We performed a systematic and detailed analysis of movements during physiological sleep using v-PSG technology.

Design: Prospective v-PSG investigation.

Setting: Academic referral center sleep laboratory.

Participants: One hundred healthy sleepers aged 19-77 years recruited from a representative population sample after a two-step screening.

Interventions: N/A.

Measurements and results: All subjects underwent v-PSG. In all cases where electromyographic activity > 100 msec duration was visible during sleep in the mentalis, submentalis, flexor digitorum superficialis, or anterior tibialis muscles, the time-synchronized video was analyzed. Visible movements were classified according to movement type and topography, and movement rates were computed for the different sleep stages. A total of 9,790 movements (median 10.2/h, IQR 4.6-16.2) were analyzed: 99.7% were elementary, 0.3% complex. Movement indices were higher in men than women (men: median 13/h, interquartile range 7.1-29.3, women: median 7.9/h, interquartile range 3.4-14.5; P = 0.006). The majority of movements involved the extremities (87.9%) and were classified as focal (53.3%), distal (79.6%), and unilateral (71.5%); 15.3% of movements were associated with arousals. REM-related movements (median 0.8 sec, IQR 0.5-1.2) were shorter than NREM-related movements (median 1.1 sec, IQR 0.8-1.6; P = 0.001). Moreover, REM-related movements were predominantly myocloniform (86.6%), whereas NREM-related movements were more often non-myocloniform (59.1%, P < 0.001).

Conclusion: Minor movements are frequent during physiological sleep, and are associated with low arousal rates. REM-related movements were predominantly myocloniform and shorter than NREM movements, indicating different influences on motor control during both sleep states.