title: Increased Sensitivity of the Circadian System to Light in Early/Mid-Puberty.
abstract: BACKGROUND
  Late adolescence is marked by a delay in sleep timing, which is partly driven by a delay shift of the circadian timing system. This study examined whether the sensitivity of the circadian system to light-the primary entraining stimulus to the circadian system-differs between pre- to mid-pubertal and late to postpubertal adolescents.
  
  
  OBJECTIVE
  The study was designed to determine the influence of puberty on the sensitivity of the circadian system to light in humans.
  
  
  METHODS
  Melatonin suppression to low and moderate light levels was assessed in 38 pre- to mid-pubertal (9.1-14.7 years) and 29 late to postpubertal (11.5-15.9 years) adolescents. They received 1 hour of four light levels on consecutive nights: approximately 0.1 (near-dark baseline condition), 15, 150, and 500 lux. One group received evening light beginning at 11:00 pm (n = 39); a second group received morning light beginning at 3:00 am (n = 28). Salivary melatonin was sampled every 30 minutes. Melatonin suppression for 15, 150, and 500 lux was calculated relative to unsuppressed baseline levels in the 0.1 lux setting, within individuals.
  
  
  RESULTS
  The pre- to mid-pubertal group showed significantly greater melatonin suppression to 15 lux (9.2 ± 20.5%), 150 lux (26.0 ± 17.7%), and 500 lux (36.9 ± 11.4%) during evening light exposure compared to the late to postpubertal group (-5.3 ± 17.7%, 12.5 ± 17.3%, and 23.9 ± 21.7%, respectively; P < .05). No significant differences were seen between developmental groups in morning melatonin suppression.
  
  
  CONCLUSIONS
  These results indicate support for a greater sensitivity to evening light in early pubertal children. The increased sensitivity to light in younger adolescents suggests that exposure to evening light could be particularly disruptive to sleep regulation for this group.
authors: Biological Rhythms Research Laboratory (S.J.C.), Department of Behavioral Sciences, Rush University Medical Center, Chicago, Illinois 60612; School of Psychological Sciences (S.W.C., A.C.B.), Monash University, Clayton, Victoria, Australia 3800; E.P. Bradley Hospital Sleep and Chronobiology Research Laboratory (C.A., M.A.C.), Providence, Rhode Island 02906; Department of Psychiatry and Human Behavior (C.A., M.A.C.), The Warren Alpert Medical School of Brown University, Providence, Rhode Island 02906; and Centre for Sleep Research (M.A.C.), University of South Australia, Adelaide, South Australia 5001.
authors: Stephanie J
authors: SJ
authors: Crowley
authors: Biological Rhythms Research Laboratory (S.J.C.), Department of Behavioral Sciences, Rush University Medical Center, Chicago, Illinois 60612; School of Psychological Sciences (S.W.C., A.C.B.), Monash University, Clayton, Victoria, Australia 3800; E.P. Bradley Hospital Sleep and Chronobiology Research Laboratory (C.A., M.A.C.), Providence, Rhode Island 02906; Department of Psychiatry and Human Behavior (C.A., M.A.C.), The Warren Alpert Medical School of Brown University, Providence, Rhode Island 02906; and Centre for Sleep Research (M.A.C.), University of South Australia, Adelaide, South Australia 5001.
authors: Sean W
authors: SW
authors: Cain
authors: Biological Rhythms Research Laboratory (S.J.C.), Department of Behavioral Sciences, Rush University Medical Center, Chicago, Illinois 60612; School of Psychological Sciences (S.W.C., A.C.B.), Monash University, Clayton, Victoria, Australia 3800; E.P. Bradley Hospital Sleep and Chronobiology Research Laboratory (C.A., M.A.C.), Providence, Rhode Island 02906; Department of Psychiatry and Human Behavior (C.A., M.A.C.), The Warren Alpert Medical School of Brown University, Providence, Rhode Island 02906; and Centre for Sleep Research (M.A.C.), University of South Australia, Adelaide, South Australia 5001.
authors: Angus C
authors: AC
authors: Burns
authors: Biological Rhythms Research Laboratory (S.J.C.), Department of Behavioral Sciences, Rush University Medical Center, Chicago, Illinois 60612; School of Psychological Sciences (S.W.C., A.C.B.), Monash University, Clayton, Victoria, Australia 3800; E.P. Bradley Hospital Sleep and Chronobiology Research Laboratory (C.A., M.A.C.), Providence, Rhode Island 02906; Department of Psychiatry and Human Behavior (C.A., M.A.C.), The Warren Alpert Medical School of Brown University, Providence, Rhode Island 02906; and Centre for Sleep Research (M.A.C.), University of South Australia, Adelaide, South Australia 5001.
authors: Christine
authors: C
authors: Acebo
authors: Biological Rhythms Research Laboratory (S.J.C.), Department of Behavioral Sciences, Rush University Medical Center, Chicago, Illinois 60612; School of Psychological Sciences (S.W.C., A.C.B.), Monash University, Clayton, Victoria, Australia 3800; E.P. Bradley Hospital Sleep and Chronobiology Research Laboratory (C.A., M.A.C.), Providence, Rhode Island 02906; Department of Psychiatry and Human Behavior (C.A., M.A.C.), The Warren Alpert Medical School of Brown University, Providence, Rhode Island 02906; and Centre for Sleep Research (M.A.C.), University of South Australia, Adelaide, South Australia 5001.
authors: Mary A
authors: MA
authors: Carskadon
mesh_terms: D000293:Adolescent; D000465:Algorithms; D002648:Child; D057906:Circadian Clocks; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism; D010775:Photic Stimulation; D011627:Puberty / Q000502:physiology*; D012463:Saliva / Q000378:metabolism; D012741:Sexual Maturation; D012890:Sleep / Q000502:physiology
chemical_list: D008550:Melatonin