Clinical and polysomnographic changes in idiopathic hypersomnia ten years after the diagnosis

Idiopathic hypersomnia (IH) is characterized by excessive daytime sleepiness and an excessive need for sleep. It is unknown whether the disorder is stable or improves with time. Our goal was to characterize the evolution of clinical and sleep patterns (including measures of excessive sleep need) in patients with IH over a ten-year period.

A standardized questionnaire focusing on the progression of clinical symptoms was sent to all patients with IH. At the time of diagnosis, all patients underwent overnight polysomnography and a multiple sleep latency test (MSLT), followed by 18-h bed rest sleep monitoring. This procedure was repeated with a subset of volunteers ten years later.

A total of 123 participants with IH (83.7% female, mean age 29 ± 11 years) were observed for an average of 9.8 ± 4.3 years and 44 of them had 48-h sleep recordings at baseline and follow-up. The percentage of patients with sleep attacks decreased from 58 to 28% and those with sleep drunkenness decreased from 93 to 79%. Nighttime sleep (restricted/unrestricted) decreased by 1- 3 h, and naps by 0.7 h. Despite these changes, 84/123 patients (68.3%) continued to experience hypersomnolence, while 39/123 patients showed improvement. No baseline clinical characteristics could predict long-term improvement. Ten years after their initial diagnosis, only 26/44 (59%) of the participants continued to meet the polysomnographic criteria for central hypersomnia.

Sleep time decreases after ten years of IH evolution, suggesting a decrease in sleep pressure with aging. However, persistent somnolence complaints indicate a stable clinical burden. Current Knowledge/Study Rationale: Idiopathic hypersomnia (IH) is a rare sleep disorder characterized by an excessive need for sleep and severe daytime sleepiness. Few studies have examined its long-term progression, and none have objectively assessed changes in sleep excess using bed rest recordings. This study re-evaluated objective sleep need in patients with IH ten years after the diagnosis using the same extended bed rest protocol. While sleep time decreases, excessive daytime sleepiness and sleep drunkenness persist. At follow-up, 41% of patients no longer met polysomnographic criteria for IH, yet most continued stimulant therapy. Complete remission remained uncommon (4%). Study Impact: These findings confirm the chronic clinical burden of IH and may prompt reconsideration of current diagnostic criteria, particularly for older patients.