title: Seasonal variations in sleep disorders of nurses.
abstract: OBJECTIVE
  To investigate the difference between nurses and the general population regarding seasonal variations in sleep disorders during 2004-2008. The effects of season and group interaction on sleep disorders with regard to different comorbidities were also examined.
  
  
  BACKGROUND
  Studies on seasonal variations in sleep disorders were mainly conducted in Norway for the general population. Furthermore, whether different comorbidities cause seasonal variations in sleep disorders in nurses remains unknown.
  
  
  METHODS
  A retrospective study.
  
  
  METHODS
  Data from the Taiwan National Health Insurance Research Database were used in generalised estimating equation Poisson distribution models to investigate the differences in sleep disorders between nurses and the general population diagnosed with sleep disorders (each n = 7643) as well as the interaction effects of sleep disorders between the groups with respect to different seasons. Furthermore, the interaction effects between groups and seasons on sleep disorders in the subgroups of comorbid anxiety disorders and depressive disorders were studied.
  
  
  RESULTS
  Both the nurses and the general population had fewer outpatient visits for sleep disorders in winter than in other seasons. The nurses had fewer outpatient visits for sleep disorders than the general population did in each season. The nurses had more outpatient visits for sleep disorders in winter than in summer compared with the general population in the comorbid depressive disorder subgroup but not in the comorbid anxiety disorder subgroup.
  
  
  CONCLUSIONS
  Nurses and the general population exhibited similar seasonal patterns of sleep disorders, but nurses had fewer outpatient visits for sleep disorders than the general population did in each season. For nurses with comorbid depressive disorders, outpatient visits for sleep disorders were more numerous in winter than in summer, potentially because nurses with comorbid depressive disorders are affected by shorter daylight exposure during winter.
  
  
  CONCLUSIONS
  Depression and daylight exposure may be considered in mitigating sleep disorders in nurses.
authors.affiliation: Graduate Institution of Long Term Care, MacKay Medical College, New Taipei City, Taiwan.|Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
authors.forename: Yuanmay
authors.initials: Y
authors.lastname: Chang
authors.affiliation: School of Nursing, College of Nursing, Taipei Medical University, Taipei, Taiwan.
authors.forename: Calvin
authors.initials: C
authors.lastname: Lam
authors.affiliation: Accelerated Bachelor of Science in Nursing, College of Nursing, Taipei Medical University, Taipei, Taiwan.
authors.forename: Su-Ru
authors.initials: SR
authors.lastname: Chen
authors.affiliation: Maternity Department, Emkhuzweni Health Center, Hhohho, Swaziland.
authors.forename: Trevor
authors.initials: T
authors.lastname: Sithole
authors.affiliation: School of Nursing, College of Nursing, Taipei Medical University, Taipei, Taiwan.
authors.forename: Min-Huey
authors.initials: MH
authors.lastname: Chung
mesh_terms: D000328:Adult; D001007:Anxiety / Q000175:diagnosis / Q000453:epidemiology; D002940:Circadian Rhythm; D015897:Comorbidity; D003863:Depression / Q000453:epidemiology; D005221:Fatigue / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009741:Nursing Staff, Hospital / Q000706:statistics & numerical data*; D009784:Occupational Diseases / Q000453:epidemiology*; D012189:Retrospective Studies; D012621:Seasons; D012890:Sleep / Q000502:physiology; D020178:Sleep Disorders, Circadian Rhythm / Q000175:diagnosis / Q000453:epidemiology*; D013624:Taiwan / Q000453:epidemiology; D014940:Work Schedule Tolerance
keywords: depression; nurses; seasonal variation; sleep disorder