title: Effects of an advanced sleep schedule and morning short wavelength light exposure on circadian phase in young adults with late sleep schedules.
abstract: OBJECTIVE
  We examined the effects of an advanced sleep/wake schedule and morning short wavelength (blue) light in 25 adults (mean age±SD=21.8±3 years; 13 women) with late sleep schedules and subclinical features of delayed sleep phase disorder (DSPD).
  
  
  METHODS
  After a baseline week, participants kept individualized, fixed, advanced 7.5-h sleep schedules for 6days. Participants were randomly assigned to groups to receive "blue" (470nm, ∼225lux, n=12) or "dim" (<1lux, n=13) light for 1h after waking each day. Head-worn "Daysimeters" measured light exposure; actigraphs and sleep diaries confirmed schedule compliance. Salivary dim light melatonin onset (DLMO), self-reported sleep, and mood were examined with 2×2 ANOVA.
  
  
  RESULTS
  After 6days, both groups showed significant circadian phase advances, but morning blue light was not associated with larger phase shifts than dim-light exposure. The average DLMO advances (mean±SD) were 1.5±1.1h in the dim light group and 1.4±0.7h in the blue light group.
  
  
  CONCLUSIONS
  Adherence to a fixed advanced sleep/wake schedule resulted in significant circadian phase shifts in young adults with subclinical DSPD with or without morning blue light exposure. Light/dark exposures associated with fixed early sleep schedules are sufficient to advance circadian phase in young adults.
authors.affiliation: Department of Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, Alpert Medical School of Brown University, Box G-RIH, Providence, RI 02912, USA. katherine_sharkey@brown.edu
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Sharkey
authors.forename: Mary A
authors.initials: MA
authors.lastname: Carskadon
authors.forename: Mariana G
authors.initials: MG
authors.lastname: Figueiro
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhu
authors.forename: Mark S
authors.initials: MS
authors.lastname: Rea
mesh_terms: D000339:Affect / Q000502:physiology / Q000528:radiation effects; D002940:Circadian Rhythm / Q000502:physiology* / Q000528:radiation effects*; D003116:Color; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism; D017440:Photoperiod; D010789:Phototherapy / Q000379:methods*; D012463:Saliva / Q000378:metabolism; D012890:Sleep / Q000502:physiology / Q000528:radiation effects; D020178:Sleep Disorders, Circadian Rhythm / Q000517:prevention & control / Q000628:therapy*; D013315:Stress, Psychological / Q000517:prevention & control / Q000628:therapy; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D008550:Melatonin