Hypersomnolence in focus: a white paper of the 6th Think Tank World Sleep Forum.

An international expert group (European Sleep Foundation Think Tank) convened in 2022 to discuss the state of the evidence in the domain of hypersomnolence. The expert group considered the current state of knowledge based on the most relevant recent publications, discussed the current challenges in the field and identified future priorities. The purpose of this white paper is to summarize the definition, diagnosis, and pathophysiology of hypersomnolence, the epidemiology, phenotype, and management of hypersomnolence in obstructive sleep apnea and in neurological and psychiatric disorders, and the impact of hypersomnolence on daily activities, workability and health-related quality of life. The key results of the discussion were that: a) hypersomnolence is both prevalent and heterogeneous in its manifestations in a wide variety of pathological conditions encompassing obstructive sleep apnea and neurological and psychiatric disorders; and b) while multiple pathophysiological pathways are potentially involved in hypersomnolence, knowledge of the specific causal factors in individual patients remains undefined, and the specific factors responsible for excessive daytime sleepiness vs. excessive need for sleep remain largely unclear. The clinical implications of these results are the occurrence of important limitations to the development of personalized approaches to diagnosis, prognosis, and management of hypersomnolence, which is essential considering the high societal and personal costs of hypersomnolence, and its substantial adverse impact on quality of life. Research priorities should address these limitations with improved quantification of hypersomnolence and with an evidence base on the costs and benefit of hypersomnolence management in patients with respiratory, neurologic, and psychiatric disorders.