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Chronotype refers to the behavioral manifestation of underlying circadian rhythms of myriad physical processes A person's chronotype is the propensity for the individual to sleep at a particular time during a 24-hour period 'Eveningness' delayed sleep period and 'morningness' advanced sleep period are the two extremes with most individuals having some flexibility in the timing of their sleep period However, across development there are changes in the propensity of the sleep period with pre-pubescent children preferring an advanced sleep period, adolescents preferring a delayed sleep period and many elderly preferring an advanced sleep period

The causes and regulation of chronotypes, including developmental change, individual propensity for a specific chronotype, and flexible versus fixed chronotypes have yet to be determined However, research is beginning to shed light on these questions, such as the relationship between age and chronotype1 There are candidate genes called clock genes that exist in most cells in the body and brain, referred to as the circadian system that regulate physiological phenomena hormone levels, metabolic function, body temperature, cognitive faculties, and sleeping With the exception of the most extreme and rigid chronotypes regulation is likely due to gene-environment interactions Important environmental cues zeitgebers include light, feeding, social behavior, and work and school schedules

Humans are normally diurnal creatures, that is to say they are active in the daytime As with most other diurnal animals, human activity-rest patterns are endogenously controlled by biological clocks with a circadian ~24-hour period

Normal variation in chronotype encompasses sleep–wake cycles that are from about two hours earlier to about two hours later than average2 Extremes outside of this range can cause a person difficulty in participating in normal work, school, and social activities If a person's "lark" or more commonly "owl" tendencies are strong and intractable to the point of disallowing normal participation in society, the person is considered to have a circadian rhythm sleep disorder3


  • 1 History
  • 2 Measurement
    • 21 Morningness–eveningness questionnaire
    • 22 Circadian Type Inventory
    • 23 Composite Scale of Morningness
    • 24 Others
  • 3 Characteristics
    • 31 Sleep
    • 32 Diurnal rhythms
    • 33 Personality
    • 34 Genetic variants associated with chronotype
    • 35 Chronotype and disease
  • 4 References


The 20th century saw greatly increased interest in and research on all questions about sleep Tremendous strides have been made in molecular, neural and medical aspects of biological rhythmicity Physiology professor Nathaniel Kleitman's 1939 book Sleep and Wakefulness, revised 1963,4 summarized the existing knowledge of sleep, and it was he who proposed the existence of a basic rest-activity cycle Kleitman, with his students including William C Dement and Eugene Aserinsky, continued his research throughout the 1900s O Öquist's 1970 thesis at the Department of Psychology, University of Göteborg, Sweden, marks the beginning of modern research into chronotypes, and is entitled Kartläggning av individuella dygnsrytmer, or "Charting Individual Circadian Rhythms"


Morningness–eveningness questionnaireedit

Olov Östberg modified Öquist's questionnaire and in 1976, together with JA Jim Horne, he published the 19-item morningness–eveningness questionnaire, MEQ,5 which is still used and referred to in virtually all research on this topic

Researchers in many countries have worked on validating the MEQ with regard to their local cultures A revision of the scoring of the MEQ as well as a component analysis was done by Jacques Taillard et al in 2004,6 working in France with employed people over the age of 50 Previously the MEQ had been validated only for subjects of university age

Circadian Type Inventoryedit

The Circadian Type Inventory, developed by Folkard 1987, is an improved version of the 20-item Circadian Type Questionnaire CTQ

Composite Scale of Morningnessedit

Smith et al 1989citation needed analyzed items from MEQ, Diurnal Type Scale, and CTQ and chose the best ones to develop an improved instrument, the 13-item Composite Scale of Morningness CSM or CS CSM consists of 9 items from the MEQ and 4 items from the Diurnal Type Scale and is regarded as an improved version of MEQ It currently exists in 14 language versions; the most recently developed are Polish,7 Russian8 and Hindi9


Roberts, in 1999, designed the Lark-Owl Chronotype Indicator, LOCIcitation needed Till Roenneberg's Munich Chronotype Questionnaire MCTQ from 2003 uses a quantitative approach; his many thousands of subjects have answered questions about their sleep behavior1011


Most people are neither evening nor morning types but lie somewhere in between Estimates vary,12 but up to half are either morning or evening people People who share a chronotype, morningness or eveningness, have similar activity-pattern timing: sleep, appetite, exercise, study etc Researchers in the field of chronobiology look for objective markers by which to measure the chronotype spectrum Paine et al13 conclude that "morningness/eveningness preference is largely independent of ethnicity, gender, and socioeconomic position, indicating that it is a stable characteristic that may be better explained by endogenous factors"


Horne and Östberg found that morning types had a higher daytime temperature with an earlier peak time than evening types and that they went to sleep and awoke earlier, but no differences in sleep lengths were found They also note that age should be considered in assessments of morningness and eveningness, noting how a "bed time of 23:30 may be indicative of a morning type within a student population, but might be more related to an evening type in the 40–60 years age group" Horne & Östberg, 1976, p 109 Clodoré et al found differences in alertness between morning and evening types after a two-hour sleep reduction14 Duffy et al investigated "changes in the phase relationship between endogenous circadian rhythms and the sleep-wake cycle", and found that although evening types woke at a later clock hour than morning types, morning types woke at a later circadian phase15 Zavada et al show that the exact hour of mid-sleep on free non-work days may be the best marker for sleep-based assessments of chronotype; it correlates well with such physiological markers as dim-light melatonin onset DLMO and the minimum of the daily cortisol rhythm16 They also state that each chronotype category "contains a similar portion of short and long sleepers" Chung et al studied sleep quality in shift-working nurses and found that "the strongest predictor of sleep quality was morningness–eveningness, not the shift schedule or shift pattern", as "evening types working on changing shifts had higher risk of poor sleep quality compared to morning types"17

Diurnal rhythmsedit

Gibertini et al18 assessed blood levels of the hormone melatonin, finding that the melatonin acrophase the time at which the peak of a rhythm occurs19 was strongly related to circadian type, whereas amplitude was not They note that morning types evidence a more rapid decline in melatonin levels after the peak than do evening types Baehr et al20 found that, in young adults, the daily body temperature minimum occurred at about 4 am for morning types but at about 6 am for evening types This minimum occurred at approximately the middle of the eight-hour sleep period for morning types, but closer to waking in evening types Evening types had a lower nocturnal temperature The temperature minimum occurred about a half-hour earlier in women than in men Similar results were found by Mongrain et al in Canada, 200421 Morning types had lower pain sensitivity throughout a day than evening types, but the two chronotype groups did not differ in the shape of diurnal variations in pain22 There are some differences between chronotypes in sexual activity, with evening chronotypes preferring later hours for sex as compared to other chronotypes23


Chronotypes differ in many aspects of personality, but also in intellectual domains, like creative thinking24 For example, eveningness preference has been related to unrestricted sociosexuality in females, but not in males25

Genetic variants associated with chronotypeedit

Some studies show that there are 22 genetic variants associated with chronotype These variants occur near genes known to be important in photoreception and circadian rhythms26 The variant most strongly associated with chronotype occurs near RGS16, which is a regulator of G-protein signalling and has a known role in circadian rhythms In mice, gene ablation of Rgs16 lengthens the circadian period of behavioural rhythm By temporally regulating cAMP signalling, Rgs16 has been shown to be a key factor in synchronising intercellular communication between pacemaker neurons in the suprachiasmatic nucleus SCN, the centre for circadian rhythm control in humans2627

PER2, is a well-known regulator of circadian rhythms and contains a variant recently shown to be associated with iris formation This suggests a link between iris function and chronotype Per2 knockout mice show arrhythmic locomotor activity262829

Therefore, the chronotype is genetically heritable30

Chronotype and diseaseedit

Disrupted circadian rhythms are associated with several human diseases, for example, chronotype is genetically correlated with BMI Body mass index263132 However, cause-and-effect is not yet determined26


  1. ^ Walker, R J; Kribs, Z D; Christopher, A N; Shewach, O R; Wieth, M B 2014 "Age, the Big Five, and time-of-day preference: A mediational model" Personality and Individual Differences 56: 170–174 doi:101016/jpaid201309003 
  2. ^ Logie, Bruce "Larks and Owls" Retrieved 2007-11-02 
  3. ^ American Academy of Sleep Medicine International Classification of Sleep Disorders, Revised Edition 2001
  4. ^ Kleitman, Nathaniel 1963 1939 Sleep and Wakefulness The University of Chicago Press 
  5. ^ Horne, JA; Östberg, O 1976 "A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms" Int J Chronobiol 4 2: 97–110 PMID 1027738 
  6. ^ Taillard, Jacques; et al 2004 "Validation of Horne and Ostberg Morningness-Eveningness Questionnaire in a Middle-Aged Population of French Workers" Journal of Biological Rhythms 19 1: 76–86 doi:101177/0748730403259849 PMID 14964706 Retrieved 2007-11-02 
  7. ^ Jankowski, KS 2014 "Composite Scale of Morningness: Psychometric properties, validity with Munich ChronoType Questionnaire and age/sex differences in Poland" European Psychiatry 30: 166–171 doi:101016/jeurpsy201401004 
  8. ^ Kolomeichuk, S 2015 "Psychometric properties of the Russian version of the Composite Scale of Morningness" Biological Rhythm Research 45 6: 725–737 doi:101080/0929101620151048963 
  9. ^ Bhatia T, Agrawal A, Beniwal RP, Thomas P, Monk TH, Nimgaonkar VL, Deshpande SN A Hindi version of the Composite Scale of Morningness Asian J Psychiatr 2013;6:581-4
  10. ^ Roenneberg, T; Kuehnle, T; Juda, M; Kantermann, T; Allebrandt, K; Gordijn, M; Merrow, M December 2007 "Epidemiology of the human circadian clock" Sleep Med Rev 11 6: 429–38 doi:101016/jsmrv200707005 PMID 17936039 
  11. ^ Allebrandt, KV; Roenneberg, T 2008 "The search for circadian clock components in humans: New perspectives for association studies" Brazilian Journal of Medical and Biological Research 41 8 doi:101590/S0100-879X2008000800013 
  12. ^ Schur, Carolyn 1994 "excerpt" Birds of a Different Feather Saskatoon, Canada: Schur Goode Associates ISBN 0-9698190-0-5 Retrieved 2009-07-20 
  13. ^ Paine, Sarah-Jane; Gander, Philippa H; Travier, Noemie 2006 "The Epidemiology of Morningness/Eveningness: Influence of Age, Gender, Ethnicity, and Socioeconomic Factors in Adults 30–49 Years" Journal of Biological Rhythms 21 1: 68–76 doi:101177/0748730405283154 PMID 16461986 Retrieved 2007-11-02 
  14. ^ Clodoré, M; Foret, J; Benoit, O 1986 "Diurnal variation in subjective and objective measures of sleepiness: the effects of sleep reduction and circadian type" Chronobiol Int 3 4: 255–63 doi:103109/07420528609079543 PMID 3677208 
  15. ^ Duffy, JF; Dijk, DJ; Hall, EF; Czeisler, CA 1999 "Relationship of endogenous circadian melatonin and temperature rhythms to self-reported preference for morning or evening activity in young and older people" J Investig Med 47 3: 141–50 PMID 10198570 
  16. ^ Zavada, Andrei; Gordijn, Beersma; Daan, Roenneberg 2005 "Comparison of the Munich Chronotype Questionnaire with the Horne-Östberg's Morningness-Eveningness Score" PDF Chronobiol Int 22 2: 267–78 doi:101081/CBI-200053536 PMID 16021843 Retrieved 2007-11-02 
  17. ^ Chung, MH; Chang, FM; Yang, CC; Kuo, TB; Hsu, N January 2009 "Sleep quality and morningness-eveningness of shift nurses" Abstract Journal of Clinical Nursing 18 2: 279–284 doi:101111/j1365-2702200702160x ISSN 1365-2702 PMID 19120754 Retrieved 2009-01-17 
  18. ^ Gibertini, M; Graham, C; Cook, MR 1999 "Self-report of circadian type reflects the phase of the melatonin rhythm" Biol psychol 50 1: 19–33 doi:101016/S0301-05119800049-0 PMID 10378437 Retrieved 2007-11-02 
  19. ^ "Dictionary of Circadian Physiology" Circadian Rhythm Laboratory, University of South Carolina Salkehatchie, Walterboro campus 
  20. ^ Baehr, EK; Revelle, W; Eastman, CI June 2000 "Individual differences in the phase and amplitude of the human circadian temperature rhythm: with an emphasis on morningness-eveningness" J Sleep Res 9 2: 117–27 doi:101046/j1365-2869200000196x PMID 10849238 
  21. ^ Mongrain, V; Lavoie, S; Selmaoui, B; Paquet, J; Dumont, M June 2004 "Phase relationships between sleep-wake cycle and underlying circadian rhythms in Morningness-Eveningness" J Biol Rhythms 19 3: 248–57 doi:101177/0748730404264365 PMID 15155011 
  22. ^ Jankowski, KS 2013 Morning types are less sensitive to pain than evening types all day long European Journal of Pain, 17, 1068-1073
  23. ^ Jankowski, KS, Díaz-Morales, JF, Randler, C 2014Chronotype, gender, and time for sex Chronobiology International, 31, 911-916
  24. ^ Giampietro, M; Cavallera, GM 2006 "Morning and evening types and creative thinking" Elsevier Ltd Retrieved 2007-11-02 
  25. ^ Jankowski, KS, Díaz-Morales, JF, Vollmer, C, Randler, C 2014 Morningness-eveningness and sociosexuality: evening females are less restricted than morning ones Personality and Individual Differences, 10, 13-17
  26. ^ a b c d e Jones, Samuel E; Tyrrell, Jessica; Wood, Andrew R; Beaumont, Robin N; Ruth, Katherine S; Tuke, Marcus A; Yaghootkar, Hanieh; Hu, Youna; Teder-Laving, Maris 2016-08-01 "Genome-Wide Association Analyses in 128,266 Individuals Identifies New Morningness and Sleep Duration Loci" PLoS genetics 12 8: e1006125 doi:101371/journalpgen1006125 ISSN 1553-7404 
  27. ^ Doi, Masao; Ishida, Atsushi; Miyake, Akiko; Sato, Miho; Komatsu, Rie; Yamazaki, Fumiyoshi; Kimura, Ikuo; Tsuchiya, Soken; Kori, Hiroshi 2011-01-01 21610730 "Circadian regulation of intracellular G-protein signalling mediates intercellular synchrony and rhythmicity in the suprachiasmatic nucleus" Check |url= value help Nature Communications 2: 327 doi:101038/ncomms1316 ISSN 2041-1723 PMID 21610730 
  28. ^ Preitner, Nicolas; Damiola, Francesca; Lopez-Molina, Luis; Zakany, Joszef; Duboule, Denis; Albrecht, Urs; Schibler, Ueli 2002-07-26 12150932+23 "The orphan nuclear receptor REV-ERBalpha controls circadian transcription within the positive limb of the mammalian circadian oscillator" Check |url= value help Cell 110 2: 251–260 ISSN 0092-8674 PMID 12150932 
  29. ^ Larsson, Mats; Duffy, David L; Zhu, Gu; Liu, Jimmy Z; Macgregor, Stuart; McRae, Allan F; Wright, Margaret J; Sturm, Richard A; Mackey, David A 2011-08-12 21835309 "GWAS findings for human iris patterns: associations with variants in genes that influence normal neuronal pattern development" Check |url= value help American Journal of Human Genetics 89 2: 334–343 doi:101016/jajhg201107011 ISSN 1537-6605 PMID 21835309 
  30. ^ von Schantz, Malcolm; Taporoski, Tamara P; Horimoto, Andréa R V R; Duarte, Nubia E; Vallada, Homero; Krieger, José E; Pedrazzoli, Mario; Negrão, André B; Pereira, Alexandre C 2015-03-18 25782397 "Distribution and heritability of diurnal preference chronotype in a rural Brazilian family-based cohort, the Baependi study" Check |url= value help Scientific Reports 5: 9214 doi:101038/srep09214 ISSN 2045-2322 PMID 25782397 
  31. ^ Kohsaka, Akira; Laposky, Aaron D; Ramsey, Kathryn Moynihan; Estrada, Carmela; Joshu, Corinne; Kobayashi, Yumiko; Turek, Fred W; Bass, Joseph 2007-11-01 17983587 "High-fat diet disrupts behavioral and molecular circadian rhythms in mice" Check |url= value help Cell Metabolism 6 5: 414–421 doi:101016/jcmet200709006 ISSN 1550-4131 PMID 17983587 
  32. ^ Turek, Fred W; Joshu, Corinne; Kohsaka, Akira; Lin, Emily; Ivanova, Ganka; McDearmon, Erin; Laposky, Aaron; Losee-Olson, Sue; Easton, Amy 2005-05-13 15845877 "Obesity and metabolic syndrome in circadian Clock mutant mice" Check |url= value help Science 308 5724: 1043–1045 doi:101126/science1108750 ISSN 1095-9203 PMID 15845877 

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