Sleep inertia measurement with the psychomotor vigilance task in idiopathic hypersomnia

Sleep inertia is a frequent and disabling symptom in idiopathic hypersomnia (IH), but poorly defined and without objective measures. The study objective was to determine whether the psychomotor vigilance task (PVT) can reliably measure sleep inertia in patients with IH or other sleep disorders (non-IH).

A total of 62 (51 women, mean age: 27.7 ± 9.2) patients with IH and 140 (71 women, age: 33.3 ± 12.1) with non-IH (narcolepsy = 29, non-specified hypersomnolence [NSH] = 47, obstructive sleep apnea = 39, insomnia = 25) were included. Sleep inertia and sleep drunkenness in the last month (M-sleep inertia) and on PVT day (D-sleep inertia) were assessed with three items of the Idiopathic Hypersomnia Severity Scale (IHSS), in drug-free conditions. The PVT was performed four times (07:00 pm, 07:00 am, 07:30 am, and 11:00 am) and three metrics were used: lapses, mean 1/reaction time (RT), and slowest 10% 1/RT.

Sleep inertia was more frequent in patients with IH than non-IH (56.5% and 43.6% with severe sleep inertia in the past month, including 24% and 12% with sleep drunkenness). Lapse number increase and slowest 10% 1/RT decrease, particularly at 07:00 am and 07:30 am, were proportional with M-sleep inertia severity, but regardless of sleep drunkenness and sleep disorders. Similar results were obtained when PVT results were compared in patients with/without D-sleep inertia, with the largest increase of the lapse number at 07:00 am and 07:30 am associated with severe sleep inertia and sleep drunkenness.

PVT is a reliable and objective measure of sleep inertia that might be useful for its characterization, management, and follow-up in patients with IH.