title: Estimating dim light melatonin onset (DLMO) phase in adolescents using summer or school-year sleep/wake schedules.
abstract: OBJECTIVE
  This analysis examined associations between the salivary dim light melatonin onset (DLMO) phase and self-selected sleep/ wake schedules in groups of children and adolescents during summer vacation and during the school year to determine the degree to which sleep/wake patterns can estimate salivary DLMO phase.
  
  
  METHODS
  Participants slept at home on self-selected schedules for 5 consecutive nights and reported their bedtime and wake-up time via daily telephone messages. Salivary melatonin was sampled in the laboratory on one evening every 30 minutes in dim light (< 50 lux) to determine DLMO phase. Within group bivariate regressions between sleep pattern measures (bedtime, wake-up time, and midsleep time) and DLMO phase were computed.
  
  
  METHODS
  One group, ages 9 to 17 years (mean age = 12.5, SD = 2.3 years, 74 males, 75 females) contributed 149 DLMO phase and sleep/wake pattern measures while on a school year schedule ("school group"). A separate group, ages 9 to 16 years (mean age = 13.1, SD = 1.3 years, 30 males, 29 females) contributed 59 DLMO phase and sleep/wake pattern measures while on a summer schedule ("summer group").
  
  
  RESULTS
  Bedtime, midsleep time, and wake-up time were positively correlated with DLMO phase in both groups. Although all correlation coefficients for the summer group were statistically greater compared to the school group, the regression equations predicted DLMO phase within +/- 1 hour of the measured DLMO phase in approximately 80% for both groups.
  
  
  CONCLUSIONS
  DLMO phase can be estimated using self-selected sleep/wake patterns during the school year or summer vacation in healthy children and adolescents.
authors.affiliation: Department of Psychology, Brown University, Providence, RI, USA. Stephanie_Crowley@Brown.edu
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Crowley
authors.forename: Christine
authors.initials: C
authors.lastname: Acebo
authors.forename: Gahan
authors.initials: G
authors.lastname: Fallone
authors.forename: Mary A
authors.initials: MA
authors.lastname: Carskadon
mesh_terms: D000293:Adolescent; D002648:Child; D002940:Circadian Rhythm / Q000502:physiology; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000032:analysis / Q000378:metabolism*; D012463:Saliva / Q000737:chemistry; D012621:Seasons; D020178:Sleep Disorders, Circadian Rhythm / Q000175:diagnosis / Q000453:epidemiology* / Q000378:metabolism*; D013334:Students / Q000706:statistics & numerical data*
chemical_list: D008550:Melatonin