title: Predictability of sleep in patients with insomnia.
abstract: OBJECTIVE
  To evaluate whether the night-to-night variability in insomnia follows specific predictable patterns and to characterize sleep patterns using objective sleep and clinical variables.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  University-affiliated sleep disorders center.
  
  
  METHODS
  146 participants suffering from chronic and primary insomnia.
  
  
  RESULTS
  Daily sleep diaries were completed for an average of 48 days and self-reported questionnaires once. Three nights were spent in the sleep laboratory for polysomnographic (PSG) assessment. Sleep efficiency, sleep onset latency, wake after sleep onset, and total sleep time were derived from sleep diaries and PSG. Time-series diary data were used to compute conditional probabilities of having an insomnia night after 1, 2, or 3 consecutive insomnia night(s). Conditional probabilities were submitted to a k-means cluster analysis. A 3-cluster solution was retained. One cluster included 38 participants exhibiting an unpredictable insomnia pattern. Another included 30 participants with a low and decreasing probability to have an insomnia night. The last cluster included 49 participants exhibiting a high probability to have insomnia every night. Clusters differed on age, insomnia severity, and mental fatigue, and on subjective sleep variables, but not on PSG sleep variables.
  
  
  CONCLUSIONS
  These findings replicate our previous study and provide additional evidence that unpredictability is a less prevalent feature of insomnia than suggested previously in the literature. The presence of the 3 clusters is discussed in term of sleep perception and sleep homeostasis dysregulation.
authors.affiliation: École de psychologie, Université Laval, Centre d'étude des troubles du sommeil, Institut universitaire en santé mentale de Québec, Québec, Canada. annie.vallieres@psy.ulaval.ca
authors.forename: Annie
authors.initials: A
authors.lastname: Vallières
authors.forename: Hans
authors.initials: H
authors.lastname: Ivers
authors.forename: Simon
authors.initials: S
authors.lastname: Beaulieu-Bonneau
authors.forename: Charles M
authors.initials: CM
authors.lastname: Morin
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales; D011581:Psychological Tests; D012720:Severity of Illness Index; D012890:Sleep; D007319:Sleep Initiation and Maintenance Disorders / Q000503:physiopathology*; D013997:Time Factors