Maintenance of a circadian phase adjustment of the human melatonin rhythm following artificial long days

Brain Res. 1993 Oct 29;626(1-2):322-6. doi: 10.1016/0006-8993(93)90595-e.


In winter, a 5-day exposure of 4 human subjects to a skeleton photoperiod, with 3 h of bright light in the evening and again in the morning, phase advanced the morning serum melatonin offset by 1-3 h as compared with the original winter melatonin rhythm pattern. The phase advance persisted for 3 days even after the bright light withdrawal. The data indicate that the long skeleton photoperiod had a prevailing phase-advancing effect on the melatonin rhythm and its underlying pacemaker. The maintenance of the phase advance might be due to the fixed sleep-wake schedule.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Circadian Rhythm / physiology*
  • Female
  • Humans
  • Male
  • Melatonin / blood
  • Photoperiod*
  • Signal Transduction / physiology*


  • Melatonin