Spectral analysis of all‐night human sleep EEG in narcoleptic patients and normal subjects

Abstract

SUMMAR Y To investigate the pathophysiology of narcoleptic patients' sleep in detail, we analysed and compared the whole-night polysomnograms of narcoleptic patients and normal human subjects. Eight drug-naive narcoleptic patients and eight age-matched normal volunteers underwent polysomnography (PSG) on two consecutive nights. In addition to conventional visual scoring of the polysomnograms, rapid eye movement (REM)-density and electroencephalograph (EEG) power spectra analyses were also performed. Sleep onset REM periods and fragmented nocturnal sleep were observed as expected in our narcoleptic patients. In the narcoleptic patients, REM period duration across the night did not show the significant increasing trend that is usually observed in normal subjects. In all narcoleptic patient REM periods, eye movement densities were significantly increased. The power spectra of narcoleptic REM sleep significantly increased between 0.3 and 0.9 Hz and decreased between 1.0 and 5.4 Hz. Further analysis revealed that non-rapid eye movement (NREM) period duration and the declining trend of delta power density in the narcoleptic patients were not significantly different from the normal subjects. Compared with normal subjects, the power spectra of narcoleptic NREM sleep increased in the 1.0-1.4 Hz and 11.0-11.9 Hz frequency bands, and decreased in a 24.0-26.9 Hz frequency band. Thus, increased EEG delta and decreased beta power densities were commonly observed in both the NREM and REM sleep of the narcoleptic patients, although the decrease in beta power during REM sleep was not statistically significant. Our visual analysis revealed fragmented nocturnal sleep and increased phasic REM components in the narcoleptic patients, which suggest the disturbance of sleep maintenance mechanism(s) and excessive effects of the mechanism(s) underlying eye movement activities during REM sleep in narcolepsy. Spectral analysis revealed significant increases in delta components and decreases in beta components, which suggest decreased activity in central arousal mechanisms. These characteristics lead us to hypothesize that two countervailing mechanisms underlie narcoleptic sleep pathology.k e y w o r d s narcolepsy, pathophysiology, power spectral analysis, rapid eye movement density, rapid eye movement sleep

Disrupted Nighttime Sleep in Narcolepsy

“…Mukai and colleagues compared PSG data between 8 drug-naïve patients with narcolepsy and 8 healthy normal controls with no history of sleep disorders. 30 Patients with narcolepsy had significantly more S1 sleep (17.2% vs. 8.9%, respectively; p < 0.01), more stage shifts (mean, 352.6 vs. 251.8, respectively; p < 0.05), and a higher percentage of WASO (3.9% vs. 1.0%, respectively; p < 0.05) than did normal controls. These investigators suggest that DNS is linked to the higher REM densities seen in patients with narcolepsy.…”

“…Thus, a total of 21 studies met the inclusion criteria ( Table 2). 14,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] …”

“…PSG comparisons between patients with narcolepsy and normal controls with no history of sleep disorders consistently find that patients with narcolepsy experience frequent brief awakenings and arousals (e.g., excessive shifts to S1 sleep or wake from deeper sleep stages), therefore having more time spent in S1 sleep, an elevated WASO, and reduced sleep efficiency relative to normal controls ( Table 4 and Figure 2). 20,23,24,[26][27][28][29][30]32 These nighttime sleep patterns are present whether or not patients are receiving stimulant medications, 20,22,32 including in drug-naïve patients with narcolepsy, 30 albeit in a small sample (N = 8), as well as when compared with other sleep disorders. 32,36 These observations provide further support for an association between narcolepsy and DNS that is also independent of stimulant use, and although the studies do not identify underlying causes of DNS, several suggest an abnormality in non-REM (NREM) sleep as a possible mediator.…”

“…43,44 In contrast, patients with narcolepsy fall asleep rapidly and experience frequent arousals but not prolonged wakefulness (Table 5). 10,[26][27][28][29][30]33,47 …”

“…Finally, studies have compared the nighttime sleep of patients with narcolepsy with the nighttime sleep of patients with , 23 Jiménez-Correa et al, 26 Mukai et al 30 other sleep disorders. 19,36 Baker et al found that patients with narcolepsy had more DNS than did patients with IH, characterized by more S1 sleep, greater WASO, and lower sleep efficiency.…”