Melatonin, sleep, and shift work adaptation

J Occup Environ Med. 2005 Sep;47(9):893-901. doi: 10.1097/01.jom.0000177336.21147.9f.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Accidents, Occupational
  • Adaptation, Physiological
  • Adult
  • Circadian Rhythm*
  • Fatigue
  • Female
  • Humans
  • Male
  • Melatonin / analogs & derivatives*
  • Melatonin / blood
  • Personnel Staffing and Scheduling*
  • Risk Factors
  • Sleep Wake Disorders / etiology*
  • Wounds and Injuries


  • Melatonin
  • 6-hydroxymelatonin