title: Attenuation of vagal recovery during sleep and reduction of cortisol/melatonin ratio in late afternoon associate with prolonged daytime sleepiness among media workers with irregular shift work.
abstract: BACKGROUND
  Media work is characterized by information flow, deadlines, and 24/7 alertness. Good recovery prevents stress-related disorders.
  
  
  METHODS
  The standardized questionnaire included items about health, health habits, sleep, work conditions, and work stress. Recordings of 24-hr heart rate variability (HRV) and four salivary samples for cortisol and melatonin levels were analyzed from 70 randomly selected workers with irregular shift work, and 70 workers with normal daytime work.
  
  
  RESULTS
  Irregular shift work increased the risk of insufficient recovery when compared to normal daytime work (OR 2.0; P < 0.05). In the group of workers with insufficient subjective recovery, HRV was attenuated (P < 0.05) during the early hours of night, and cortisol/melatonin ratio was decreased (P < 0.05) in the afternoon.
  
  
  CONCLUSIONS
  Physiological changes underlying subjective feelings of insufficient recovery are measurable. Attenuated HRV during sleep reflects prolonged sympathetic drive and/or impaired parasympathetic recovery. Interactions between cortisol and melatonin hormones might be involved in the development of chronic exhaustion.
authors.affiliation: Finnish Institute of Occupational Health, Centre of Excellence of Health and Work Ability, Helsinki, Finland. harri.lindholm@ttl.fi
authors.forename: Harri
authors.initials: H
authors.lastname: Lindholm
authors.forename: Juha
authors.initials: J
authors.lastname: Sinisalo
authors.forename: Jari
authors.initials: J
authors.lastname: Ahlberg
authors.forename: Ari
authors.initials: A
authors.lastname: Hirvonen
authors.forename: Christer
authors.initials: C
authors.lastname: Hublin
authors.forename: Markku
authors.initials: M
authors.lastname: Partinen
authors.forename: Aslak
authors.initials: A
authors.lastname: Savolainen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016009:Chi-Square Distribution; D002940:Circadian Rhythm; D016001:Confidence Intervals; D005260:Female; D005387:Finland; D006305:Health Status Indicators; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D008297:Male; D008402:Mass Media; D008550:Melatonin / Q000032:analysis*; D016017:Odds Ratio; D012463:Saliva; D057566:Self Report; D012890:Sleep / Q000502:physiology*; D013223:Statistics as Topic; D011795:Surveys and Questionnaires; D013997:Time Factors; D014940:Work Schedule Tolerance / Q000502:physiology* / Q000523:psychology
chemical_list: D008550:Melatonin; D006854:Hydrocortisone