Periodic movements in sleep and sleep-wake complaint.

Periodic movements during sleep (PMS) are frequent, involuntary movements, usually of the lower extremities, that disrupt sleep. Twelve patients (nine men and three women, mean age 53.9 years) with a complaint of persistent insomnia (DIMS) were compared with 11 patients (eight men and three women, mean age 53.0 years) complaining of excessive daytime sleepiness (DOES). DIMS patients had more PMS (both absolute and relative), a longer delay to sleep onset and to REM onset, more wakefulness after sleep onset, and less total sleep time. Although the fragmentation of physiological sleep was more severe in the DIMS patients, those individuals with DOES reported cognitive intrusions during their sleep. While DOES patients may be regarded as "sleeping through" the brief arousals associated with leg activity during sleep, there appears to be sufficient cognitive awareness of the nocturnal interruption to precipitate a complaint of daytime sleepiness. Insomnia patients, however, appear to experience longer and more frequent awakenings, which are proportional to increased fragmentation of sleep.