title: Melatonin, sleep, and shift work adaptation.
abstract: BACKGROUND
  Night work is associated with disrupted circadian rhythms, fatigue, accidents, and chronic disease. Melatonin secretion helps regulate sleep and circadian rhythms.
  
  
  OBJECTIVE
  Melatonin, sleep disturbances, and symptoms (sleep, fatigue, mental) were compared among workers on permanent day, swing, and night shifts.
  
  
  METHODS
  Urinary 6-hydroxymelatonin sulfate (6-OHMS) was measured in postwork and postsleep samples. Disrupted circadian melatonin production was evaluated using the sleep:work 6-OHMS ratio. Wrist actigraphy characterized light exposures and sleep characteristics.
  
  
  RESULTS
  Night workers had altered melatonin, disrupted sleep, and elevated symptom prevalence. Subjects grouped by their sleep:work 6-OHMS ratio rather than shift had even greater symptom prevalence. Risks for two or more symptoms were 3.5 to 8 times greater among workers with sleep:work ratios < or =1 compared to those with ratios >1.
  
  
  CONCLUSIONS
  This ratio may help identify workers at increased risk for accidents or injuries.
authors.affiliation: Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, USA. burch@gwm.sc.edu
authors.forename: James B
authors.initials: JB
authors.lastname: Burch
authors.forename: Michael G
authors.initials: MG
authors.lastname: Yost
authors.forename: Wendy
authors.initials: W
authors.lastname: Johnson
authors.forename: Emily
authors.initials: E
authors.lastname: Allen
mesh_terms: D000062:Accidents, Occupational; D000222:Adaptation, Physiological; D000328:Adult; D002940:Circadian Rhythm; D005221:Fatigue; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives* / Q000097:blood; D010561:Personnel Staffing and Scheduling; D012307:Risk Factors; D012893:Sleep Wake Disorders / Q000209:etiology*; D014947:Wounds and Injuries
chemical_list: D008550:Melatonin; C012365:6-hydroxymelatonin