Résumé
Objective: To evaluate the associations between cerebrospinal
fluid orexin-A (ORX) levels and markers of nocturnal sleep stability,
assessed by polysomnography (PSG). Methods: Nocturnal PSG data and ORX
levels of 300 drug-free subjects (55% men, 29.9±15.5 years, ORX level
155.1±153.7 pg/ml) with hypersomnolence were collected. Several markers of
nocturnal sleep stability were analyzed: wake and sleep bouts, sleep/wake
transitions. Groups were categorized according to ORX levels, in two
categories (deficient≤110; >110), in tertiles (≤26, ]26;254],
>254), and compared using logistic regression models. Results were
adjusted for age, sex and body mass index. Results: We found higher number
of wake bouts (43 vs 25, p<0.0001), sleep bouts (43 vs 25.5,
p<0.0001) and index of sleep bouts/hour of sleep time, but lower
index of wake bouts/hour of waketime (41.4 vs 50.6, p<0.0001) in
subjects with ORX deficiency. The percentage of wake bouts <30sec
was lower (51.3 vs 60.8%, p<0.001) and of wake bouts ³1min30sec
higher (7.7 vs 6.7%, p=0.02) when ORX deficient. The percentage of sleep
bouts ≤14min was higher (2-5min: 23.7 vs 16.1%, p<0.0001), and of
long sleep bouts lower (>32min30sec: 7.3 vs 18.3%, p<0.0001)
when ORX deficient. These findings were confirmed when groups were
categorized according to ORX tertiles, with a dose-response effect of ORX
levels in post-hoc comparisons, and in adjusted models. Interpretation:
This study shows an association between ORX levels and nocturnal sleep
stabilization in patients with hypersomnolence. Sleep and wake bouts are
reliable markers of nighttime sleep stability that correlate with CSF ORX
levels in a dose-dependent manner.