Résumé
Idiopathic hypersomnia (IH) and narcolepsy type 2 (NT2) are rare hypersomnolence disorders with unknown pathophysiology. Recent evidence suggests they may belong to the same spectrum. This study compared objective sleep duration and REM sleep features, including sleep-onset REM periods (SOREMPs), during a 32-hour continuous polysomnography (PSG) in patients with confirmed NT2 or IH.
Consecutive drug-free patients with sleepiness complaint underwent baseline PSG and multiple sleep latency test (MSLT) and were included if their mean sleep latency was ≤8 minutes, with a clear NT2 or IH diagnosis. They were classified into three groups based on baseline SOREMPs (0, 1, or ≥2). During a second visit, they underwent a 32-hour bedrest protocol with continuous PSG under controlled conditions.
Of 84 patients (mean age 28.6±8.9 years, 70.2% female), 22 had ≥2 SOREMPs (NT2), 16 had 1 (IH), and 46 had none (IH) at baseline PSG/MLST. Surprisingly, total sleep duration during the 32-hour bedrest and SOREMP count did not differ between the three groups. However, the ≥2 SOREMPs-group had longer REM sleep duration, more REM sleep bouts, and more REM/Wake transitions during bedrest. Patients with 1 or ≥2 SOREMPs also showed a higher REM sleep proportion at baseline than those without SOREMPs.
Total sleep time and number of SOREMPs during prolonged PSG did not differ between IH and NT2. NT2 patients, however, exhibited more REM sleep and REM/Wake transitions. Overall, our data on sleep time and SOREMPs frequency support IH and NT2 as a single disease entity.