B. Dantz et al., CIRCADIAN-RHYTHMS IN NARCOLEPSY - STUDIES ON A 90 MINUTE DAY, Electroencephalography and clinical neurophysiology, 90(1), 1994, pp. 24-35
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.