title: Nocturnal light effects on menstrual cycle length.
abstract: OBJECTIVE
  In previous University of California, San Diego (UCSD) studies, nocturnal illumination shortened menstrual cycles that were longer than 33 days. The studies reported here extend the previous findings, confining the illumination to the sleep period.
  
  
  METHODS
  Two light levels (235 to 250 lux and less than 1 lux) and 2 modes of light delivery (lighted sleep mask and bedside lamp) were tested.
  
  
  RESULTS
  235 to 250 lux treatment cycle lengths were significantly shorter than baseline, but not significantly shorter than the less than 1 lux treatment cycle lengths. Subjective reports of sleep disturbance were greater with the 235 to 250 lux treatment, but there was no significant difference in overall quality of sleep between the two light levels.
  
  
  CONCLUSIONS
  The current data alone do not exclude spontaneous remission or suggestion, but our previous studies demonstrated significant contrasts between 235 to 250 lux and less than 1 lux light levels. This study suggests that treatment may be effective when confined to the sleep period, and that light masks, which do not disturb bed partners, may be used in place of bedside lamps.
authors.affiliation: Department of Psychiatry, University of California, San Diego, La Jolla, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Rex
authors.forename: D F
authors.initials: DF
authors.lastname: Kripke
authors.forename: R J
authors.initials: RJ
authors.lastname: Cole
authors.forename: M R
authors.initials: MR
authors.lastname: Klauber
mesh_terms: D000293:Adolescent; D000328:Adult; D002940:Circadian Rhythm; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008597:Menstrual Cycle / Q000502:physiology*; D010789:Phototherapy; D011446:Prospective Studies; D012189:Retrospective Studies; D013997:Time Factors