title: Differences in cortisol profiles and circadian adjustment time between nurses working night shifts and regular day shifts: A prospective longitudinal study.
abstract: OBJECTIVE
  This study explored the differences in the circadian salivary cortisol profiles between nurses working night shifts and regular day shifts following a slow rotating shift schedule to assess the number of days required for adjusting the circadian rhythm of salivary cortisol levels in nurses working consecutive night shifts and the number of days off required to restore the diurnal circadian rhythm of salivary cortisol levels.
  
  
  METHODS
  This was a prospective, longitudinal, parallel-group comparative study. The participants were randomly assigned to night and day-shift groups, and saliva samples were collected to measure their cortisol levels and circadian secretion patterns.
  
  
  RESULTS
  Significant differences were observed in the overall salivary cortisol pattern parameters (cortisol awakening response, changes in cortisol profiles between 6 and 12h after awakening, and changes in cortisol profiles between 30 min and 12 h after awakening) from Days 2 to 4 of the workdays between both groups. However, on Day 2 of the days off, both groups exhibited similar cortisol profiles and the cortisol profiles in the night-shift group were restored.
  
  
  CONCLUSIONS
  Nurses working night shifts require at least 4 days to adjust their circadian rhythms of cortisol secretions. Moreover, on changing from night shift to other shifts, nurses must be allowed more than 2 days off work.
authors.affiliation: Department of Nursing, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan; Graduate Institute of Nursing, College of Nursing, Taipei Medical University, Taipei, Taiwan; Department of Nursing, Fu Jen Catholic University, Taipei, Taiwan.
authors.forename: Shu-Fen
authors.initials: SF
authors.lastname: Niu
authors.affiliation: Graduate Institute of Nursing, College of Nursing, Taipei Medical University, Taipei, Taiwan.
authors.forename: Min-Huey
authors.initials: MH
authors.lastname: Chung
authors.affiliation: Department of Neurology, Tri-Service General Hospital, Taipei, Taiwan; Institute of Aerospace and Undersea Medicine, School of Medicine, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Hsin
authors.initials: H
authors.lastname: Chu
authors.affiliation: Department of Nursing, Taipei Medical University-Shuang Ho Hospital, Taipei, Taiwan.
authors.forename: Jui-Chen
authors.initials: JC
authors.lastname: Tsai
authors.affiliation: Department of Neurology, Tri-Service General Hospital, Taipei, Taiwan.
authors.forename: Chun-Chieh
authors.initials: CC
authors.lastname: Lin
authors.affiliation: Graduate Institute of Nursing, College of Nursing, Taipei Medical University, Taipei, Taiwan.
authors.forename: Yuan-Mei
authors.initials: YM
authors.lastname: Liao
authors.affiliation: Graduate Institute of Biomedical Materials and Tissue Engineering, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan; Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei, Taiwan; Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei, Taiwan; Department of Dentistry, Taipei Medical University-Shuang-Ho Hospital, Taipei, Taiwan.
authors.forename: Keng-Liang
authors.initials: KL
authors.lastname: Ou
authors.affiliation: Clinical Nursing, Centre for Practice Opportunity and Development, Australia; Faculty of Health and Medicine, School of Nursing and Midwifery, The university of Newcastle, Australia.
authors.forename: Anthony Paul
authors.initials: AP
authors.lastname: O'Brien
authors.affiliation: Graduate Institute of Nursing, College of Nursing, Taipei Medical University, Taipei, Taiwan; Department of Nursing, Taipei Medical University-Shuang Ho Hospital, Taipei, Taiwan; Psychiatric Research Center, Taipei Medical University Hospital, Taipei, Taiwan. Electronic address: kueiru@tmu.edu.tw.
authors.forename: Kuei-Ru
authors.initials: KR
authors.lastname: Chou
mesh_terms: D002940:Circadian Rhythm; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D008137:Longitudinal Studies; D009741:Nursing Staff, Hospital; D011446:Prospective Studies; D011897:Random Allocation; D012463:Saliva / Q000737:chemistry*; D014940:Work Schedule Tolerance
chemical_list: D006854:Hydrocortisone
keywords: Circadian rhythm; Cortisol; Night shift; Nurses; Shift work