Idiopathic hypersomnia (IH) is characterized by non-restoring night-time sleep, excessive daytime sleepiness, sleep inertia, impaired cognitive functioning and autonomic symptoms. IH seems to be long lasting, once established, but little is known about long-time consequences, and research on the relationship between idiopathic hypersomnia and all-cause mortality is however sparse. IH is thus a poorly characterized disorder of hypersomnolence, and the present study aims to answer the following research questions:

1. Are there subgroups within the IH-group, that can be retrospectively characterized out of data from polysomnography, PSG and MSLT.
2. What are the relationships between IH, and possible IH subgroups, and morbidity, mortality, and sick leave, using retrospective register data?
3. What is the natural course of IH, and possible IH subgroups, assessed with questionnaires that measures daytime sleepiness, depression, and insomnia?
4. How do subjects diagnosed with IH think about their disease, cope with it, and perceive the effects of treatments, using qualitative interviews? 185 individuals assessed and diagnosed at the Sleep unit, Uppsala university hospital between 2010-01-01 and 2019-12-31 will be contacted. After collecting informed consents, PSG and MSLT data will be analysed together with register data regarding morbidity, mortality, sick leave, and pharmacotherapy.Questionnaires used at the time of the original assessment will be reviewed and, to study the natural course of the syndrome, the same questionnaires will be sent to the participants by mail.

Inclusion Criteria:

• Idiopathic hypersomnia, according to the The International Classification of Sleep Disorders - Third Edition (ICSD-3)

Exclusion Criteria:

• Other serious somatic or psychiatric disease
• Drug additction with drug seeking behaviour

Eligible subjects are 185 individuals with idiopathic hypersomnia (IH) assessed and diagnosed using polysomnography and multiple sleep latency test at the Sleep unit, Uppsala university hospital between 2010-01-01 and 2019-12-31. Inclusion criteria is IH, according to the ICSD-3.