CIRCADIAN-RHYTHMS IN NARCOLEPSY - STUDIES ON A 90 MINUTE DAY

Following a baseline night recording, 8 narcoleptic subjects and 8 sex - and age-matched controls were maintained on a 90 min sleep/wake sche dule for 48-72 h. Each cycle consisted of 60 min of enforced wakefulne ss out of bed, followed by a 30 min ''nap'' period in which subjects w ere asked to try and fall asleep. Upon completion of the 90 min sleep/ wake protocol, subjects were permitted to sleep ad libitum for 24 h. A ll sleep periods were monitored polygraphically; in addition, tympanic temperature and subjective sleepiness were recorded during the 90 min sleep/wake schedule. Narcoleptics and controls differed dramatically in their sleep patterns during the 90 min sleep/wake schedule. On aver age, narcoleptics obtained 2 more hours per day of total sleep time (T ST) than did the controls, with REM sleep comprising nearly 2/3 of the incremental sleep time. The two groups did not differ with respect to the amount of slow wave sleep (stage 3+4; SWS). The sleep latency rhy thms observed in control subjects were markedly diminished in narcolep tics; narcoleptic subjects remained objectively sleepy (i.e., had low sleep latencies) even at times corresponding to maximum alertness in t he control subjects. Rhythms in subjective sleepiness and core tempera ture were, however, robust in both groups. Although TST in narcoleptic s exceeded that of controls during the 90 min sleep/wake schedule, nar coleptics did not obtain more sleep than controls during the baseline or recovery periods. These findings suggest that the homeostatic proce ss of sleep regulation is intact in narcoleptics. Moreover, it appears that the circadian clock itself is functioning normally in narcolepti cs. An attenuated clock effector mechanism responsible for promoting a lertness may, however, explain excessive daytime sleepiness in narcole ptics.