Effects of zopiclone on slow wave sleep and spontaneous K-complexes for normal healthy young adults

Benzodiazepine (BZD) hypnotics have been known to decrease, to some degree, human slow wave sleep (SWS) although they elevate the arousal threshold during sleep. Zopiclone (ZPC), a cyclopyrrolone hypnotic, has attracted the interest of sleep researchers because an increase in human SWS has been reported. Since the increase has not been fully confirmed by all of the studies, the authors investigated the effects of ZPC 10 mg on SWS and the K-complexes for 7 healthy young adults because there is evidence indicating that delta waves consisting of SWS and the spontaneous K-complexes are identical. SWS and st. 4 sleep did not decrease on any of the ZPC nights but st. 3 sleep showed a tendency to reduce on the 1st ZPC night. The frequency of the K-complexes decreased significantly on the 2nd ZPC night and tended to reduce on the 1st ZPC night. Moreover, a significant positive correlation was noted between the decrease rates of SWS and the K-complexes on both the ZPC nights. The authors, therefore, could not obtain any findings suggesting an increase in SWS with ZPC.