title: Epidemiology of the human circadian clock.
abstract: Humans show large inter-individual differences in organising their behaviour within the 24-h day-this is most obvious in their preferred timing of sleep and wakefulness. Sleep and wake times show a near-Gaussian distribution in a given population, with extreme early types waking up when extreme late types fall asleep. This distribution is predominantly based on differences in an individuals' circadian clock. The relationship between the circadian system and different "chronotypes" is formally and genetically well established in experimental studies in organisms ranging from unicells to mammals. To investigate the epidemiology of the human circadian clock, we developed a simple questionnaire (Munich ChronoType Questionnaire, MCTQ) to assess chronotype. So far, more than 55,000 people have completed the MCTQ, which has been validated with respect to the Horne-Østberg morningness-eveningness questionnaire (MEQ), objective measures of activity and rest (sleep-logs and actimetry), and physiological parameters. As a result of this large survey, we established an algorithm which optimises chronotype assessment by incorporating the information on timing of sleep and wakefulness for both work and free days. The timing and duration of sleep are generally independent. However, when the two are analysed separately for work and free days, sleep duration strongly depends on chronotype. In addition, chronotype is both age- and sex-dependent.
authors.affiliation: Centre for Chronobiology, Institute for Medical Psychology, University of Munich, Goethestrasse 31, 80336 Munich, Germany. roenneberg@lmu.de
authors.forename: Till
authors.initials: T
authors.lastname: Roenneberg
authors.forename: Tim
authors.initials: T
authors.lastname: Kuehnle
authors.forename: Myriam
authors.initials: M
authors.lastname: Juda
authors.forename: Thomas
authors.initials: T
authors.lastname: Kantermann
authors.forename: Karla
authors.initials: K
authors.lastname: Allebrandt
authors.forename: Marijke
authors.initials: M
authors.lastname: Gordijn
authors.forename: Martha
authors.initials: M
authors.lastname: Merrow
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000465:Algorithms; D001683:Biological Clocks / Q000502:physiology*; D002648:Child; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011159:Population Surveillance; D011594:Psychometrics; D012016:Reference Values; D017678:Sex Distribution; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*; D020178:Sleep Disorders, Circadian Rhythm / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D011795:Surveys and Questionnaires; D014851:Wakefulness / Q000502:physiology*