title: Sleep and chronobiology in cluster headache.
abstract: OBJECTIVE
  Cluster headache (CH) is the headache disorder with the strongest chronobiological traits. The severe attacks of pain occur with diurnal and annual rhythmicity but the precise rhythm and involvement of potential zeitgebers is unknown. Patients complain of poor sleep quality yet this has never been studied. We investigated triggers, rhythms, sleep quality and chronotypes in CH.
  
  
  METHODS
  Patients and controls completed questionnaires and structured interviews composed of new and previously validated parts including the Pittsburgh Sleep Quality Index (PSQI) and Morningness-Eveningness Questionnaire (MEQ). Patients were characterized by a CH index, a unified measure of headache burden.
  
  
  RESULTS
  A total of 275 CH patients and 145 matched controls were included. The most common trigger was sleep (80%) and a relationship between clusters and daylight was identified. Of the patients, 82.2% reported diurnal and 56% annual rhythmicity. Patients reported impaired sleep quality (PSQI) (p < 0.0001) and an inverse relationship between time passed since last attack and sleep quality was identified (p < 0.0001). The CH index was positively related to the PSQI (p < 0.0001).
  
  
  CONCLUSIONS
  Diurnally, CH exhibits a relationship with night-time and annually with daylight hours. Patients' sleep quality is reduced compared with controls. Results suggest a complex relationship as sleep quality improves between clusters, but remains pathological.
authors.affiliation: Danish Headache Center, Dept. of Neurology.
authors.forename: M
authors.initials: M
authors.lastname: Barloese
authors.affiliation: Danish Headache Center, Dept. of Neurology.
authors.forename: N
authors.initials: N
authors.lastname: Lund
authors.affiliation: Danish Headache Center, Dept. of Neurology.
authors.forename: A
authors.initials: A
authors.lastname: Petersen
authors.affiliation: Danish Headache Center, Dept. of Neurology.
authors.forename: M
authors.initials: M
authors.lastname: Rasmussen
authors.affiliation: Danish Center for Sleep Medicine, Dept. of Neurophysiology, Glostrup Hospital, University of Copenhagen, Denmark.
authors.forename: P
authors.initials: P
authors.lastname: Jennum
authors.affiliation: Danish Headache Center, Dept. of Neurology rigmor.jensen@regionh.dk.
authors.forename: R
authors.initials: R
authors.lastname: Jensen
mesh_terms: D000328:Adult; D003027:Cluster Headache / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010507:Periodicity; D012890:Sleep / Q000502:physiology*; D011795:Surveys and Questionnaires
keywords: Cluster headache; chronobiology; hypothalamus; pain; sleep