Intrinsic circadian period of adolescent humans measured in conditions of forced desynchrony

Neurosci Lett. 1999 Jan 29;260(2):129-32. doi: 10.1016/s0304-3940(98)00971-9.


Circadian timing was assessed with forced desynchrony (FD) in 10 healthy adolescents (five boys, five girls; mean age 13.7 years). Following 10 days of entrainment to a fixed light-dark (LD) schedule at home, participants were studied under dim light (<20 lux) in the laboratory. A 28-h schedule (FD) was imposed for 12 x 28-h cycles. Saliva was collected at 30- or 60-min intervals throughout; core temperature was measured in constant routines (CR) before and after FD. Intrinsic circadian period was estimated by linear regression using temperature minimum from CRs and dim-light salivary melatonin onsets and offsets from FD. Average intrinsic circadian period for core temperature (n = 7) was 24.30+/-0.20, for melatonin onset was 24.33+/-0.21, and for melatonin offset was 24.35+/-0.21. Intrinsic circadian period in every adolescent was greater than 24 h.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Body Temperature / physiology
  • Child
  • Circadian Rhythm / physiology*
  • Female
  • Humans
  • Light
  • Male
  • Melatonin / analysis
  • Saliva / chemistry
  • Saliva / physiology


  • Melatonin