Larger phase angle between sleep propensity and melatonin rhythms in sighted humans with non-24-hour sleep-wake syndrome

Sleep. 2002 Feb 1;25(1):83-8. doi: 10.1093/sleep/25.1.83.


Study objectives: This study was aimed to clarify phase angle between sleep propensity and the circadian pacemaker in patients with non-24-hour sleep-wake syndrome (Non-24).

Design and setting: A case-control study was underaken.

Participants: Sighted patient with Non-24 (4 males and 1 female, aged 16 to 39 y), and sex- and age-matched healthy controls (12 males and 3 females, aged 19 to 35 y) participated the study. MEASUREMENT AND INTERVENTION: Following an actigraphic assessment of the sleep-wake cycle in their homes, the participants entered an ultra-short sleep-wake schedule together with simultaneous measurement of dim light melatonin rhythm after 24-hour sleep deprivation.

Results: The period of the sleep-wake cycle observed at home was longer in the Non-24 patients (25.12 hours) than in the controls (24.02 hours, p<0.0001). The interval from sleep propensity (SP) onset to the melatonin midpoint (MLmid) was significantly shorter in the Non-24 patients than in the controls. The interval from the MLmid to the SP offset was significantly longer in the Non-24 patients than in the controls.

Conclusions: It was postulated that Non-24 sufferers' delayed SP onset relative to the circadian pacemaker may accelerate the light-induced phase-delay, leading to sleep-wake cycle that is longer than 24 hours.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Case-Control Studies
  • Circadian Rhythm / physiology
  • Female
  • Humans
  • Male
  • Melatonin / blood
  • Melatonin / metabolism*
  • Polysomnography
  • Sleep Disorders, Circadian Rhythm / diagnosis
  • Sleep Disorders, Circadian Rhythm / epidemiology
  • Sleep Disorders, Circadian Rhythm / metabolism*


  • Melatonin