title: Phase advancing human circadian rhythms with morning bright light, afternoon melatonin, and gradually shifted sleep: can we reduce morning bright-light duration?
abstract: OBJECTIVE
  Efficient treatments to phase-advance human circadian rhythms are needed to attenuate circadian misalignment and the associated negative health outcomes that accompany early-morning shift work, early school start times, jet lag, and delayed sleep phase disorder. This study compared three morning bright-light exposure patterns from a single light box (to mimic home treatment) in combination with afternoon melatonin.
  
  
  METHODS
  Fifty adults (27 males) aged 25.9 ± 5.1 years participated. Sleep/dark was advanced 1 h/day for three treatment days. Participants took 0.5 mg of melatonin 5 h before the baseline bedtime on treatment day 1, and an hour earlier each treatment day. They were exposed to one of three bright-light (~5000 lux) patterns upon waking each morning: four 30-min exposures separated by 30 min of room light (2-h group), four 15-min exposures separated by 45 min of room light (1-h group), and one 30-min exposure (0.5-h group). Dim-light melatonin onsets (DLMOs) before and after treatment determined the phase advance.
  
  
  RESULTS
  Compared to the 2-h group (phase shift = 2.4 ± 0.8 h), smaller phase-advance shifts were seen in the 1-h (1.7 ± 0.7 h) and 0.5-h (1.8 ± 0.8 h) groups. The 2-h pattern produced the largest phase advance; however, the single 30-min bright-light exposure was as effective as 1 h of bright light spread over 3.25 h, and it produced 75% of the phase shift observed with 2 h of bright light.
  
  
  CONCLUSIONS
  A 30-min morning bright-light exposure with afternoon melatonin is an efficient treatment to phase-advance human circadian rhythms.
authors.affiliation: Biological Rhythms Research Laboratory, Department of Behavioral Sciences, Rush University Medical Center, 1645 West Jackson Blvd. Suite 425, Chicago, IL 60612, USA. Electronic address: stephanie_j_crowley@rush.edu.
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Crowley
authors.affiliation: Biological Rhythms Research Laboratory, Department of Behavioral Sciences, Rush University Medical Center, 1645 West Jackson Blvd. Suite 425, Chicago, IL 60612, USA.
authors.forename: Charmane I
authors.initials: CI
authors.lastname: Eastman
mesh_terms: D056044:Actigraphy; D000328:Adult; D002940:Circadian Rhythm / Q000187:drug effects* / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000008:administration & dosage / Q000494:pharmacology*; D012890:Sleep / Q000187:drug effects* / Q000528:radiation effects*; D013997:Time Factors
chemical_list: D008550:Melatonin
keywords: Bright light; Circadian misalignment; Circadian rhythms; DLMO; Jet lag; Melatonin