[Non-24-hour sleep-wake syndrome].

The sleep-wake cycle in non-24-hour sleep-wake syndrome is longer than 24 hours. Patients go to bed a little bit later each day and then can not fall asleep and wake up at the usual time. The same sleep patterns and free running rhythms in healthy subjects have been seen in temporal isolation. The mechanism of this syndrome has not been clarified, but several factors have been proposed as follows: 1) the weakness of Zeitgeber 2) decrease of sensitivity to Zeitgeber 3) the period of the circadian system is much longer than 24 hours. Vitamin B12 and melatonin were reported to be effective in treating this syndrome.