Chronotype: What It Is and How to Check Your Own Sleep Timing
Chronotype is your preferred timing of sleep within 24 hours. Learn what it means, how researchers measure it, and how to audit your own sleep timing records.
A chronotype is the behavioral manifestation of an underlying circadian rhythm's myriad physical processes.
A person's chronotype is the propensity for the individual to sleep at a particular time during a 24-hour period.
Morningness, eveningness, and the range in between
Eveningness (delayed sleep period) and morningness (advanced sleep period) are the two extreme chronotype poles.
Most individuals have flexibility in the timing of their sleep period rather than being strictly morning or evening types.
Normal variation in chronotype encompasses sleep–wake cycles that are two to three hours later in evening types than in morning types.
Extremely delayed or advanced chronotypes outside the common range can cause difficulty participating in normal work, school, and social activities and may be considered a circadian rhythm sleep disorder.
How chronotype shifts across the lifespan
Across development, pre-pubescent children tend to prefer an advanced sleep period.
Across development, adolescents prefer a delayed sleep period.
Across development, many elderly prefer an advanced sleep period.
A 2007 survey by Roenneberg et al. of over 55,000 people showed morningness–eveningness tends to follow a normal distribution.
Paine et al. conclude that morningness/eveningness preference is largely independent of ethnicity, gender, and socioeconomic position.
Biology, environment, and proposed explanations
There are candidate CLOCK genes in most body and brain cells that are part of the circadian system regulating physiological phenomena.
Regulation of chronotypes is likely due to gene–environment interactions, with important environmental cues (zeitgebers) including light, feeding, social behavior, and work and school schedules.
An evolutionary link between chronotype and nighttime vigilance in ancestral societies has been proposed.
Chronotypes have been investigated in other species such as fruit flies and mice.
A brief history of chronotype research
Nathaniel Kleitman's 1939 book Sleep and Wakefulness summarized existing sleep knowledge and proposed a basic rest-activity cycle.
Sleep and Wakefulness was revised in 1963 by Kleitman.
O. Öquist's 1970 thesis marks the beginning of modern research into chronotypes.
O. Öquist completed a thesis titled Charting Individual Circadian Rhythms in 1970, marking the start of modern chronotype research.
Questionnaires and tools
Olov Östberg and J.A. Horne published the 19-item Morningness–Eveningness Questionnaire (MEQ) in 1976, which remains widely used in chronotype research.
The Circadian Type Inventory (CTI), developed by Folkard in 1987, assesses rigidity/flexibility of sleeping habits and the ability to overcome drowsiness for shift-work adaptation.
The Composite Scale of Morningness (CSM), developed by Smith et al. in 1989, is a 13-item instrument combining items from the MEQ and the Diurnal Type Scale and exists in multiple language versions.
Roberts designed the Lark-Owl Chronotype Indicator (LOCI) in 1999.
Till Roenneberg developed the Munich Chronotype Questionnaire (MCTQ) in 2003 using a quantitative approach.
Jacques Taillard et al. revised MEQ scoring and component analysis in 2004 in a study of employed people over age 50.
Roenneberg et al. published a survey in 2007 of over 55,000 people showing morningness–eveningness follows a normal distribution.
Michael J. Breus proposed four main chronotype categories in 2016 labeled lions, bears, wolves, and dolphins.
Physiological markers linked with chronotype
Horne and Östberg found that morning types have a higher daytime temperature with an earlier peak time than evening types.
Horne and Östberg found no differences in sleep length between morning types and evening types.
Mid-sleep on free days may be the best marker for sleep-based assessments of chronotype.
Mid-sleep on free days correlates well with physiological markers such as dim-light melatonin onset (DLMO) and the daily cortisol minimum.
Gibertini et al. (1999) found that melatonin acrophase time is strongly related to circadian type while melatonin amplitude is not.
Chung et al. reported that morningness–eveningness was the strongest predictor of sleep quality in shift-working nurses, more than shift schedule or pattern.
Popular labels and how they relate to research terms
Eveningness describes a delayed sleep period at one extreme of the chronotype range.
Morningness describes an advanced sleep period at the other extreme of the chronotype range.
Michael J. Breus proposed four main chronotype categories labeled lions, bears, wolves, and dolphins, which offer one way of grouping individual sleep timing preferences.
How to audit your own records for chronotype
The Morningness–Eveningness Questionnaire (MEQ) is a structured way to score where you tend to fall between morningness and eveningness, and it remains widely used in chronotype research.
The Circadian Type Inventory (CTI) was developed to assess rigidity or flexibility of sleeping habits and the ability to overcome drowsiness for shift-work adaptation, so CTI-style checklists can guide you to pay attention to how fixed or adaptable your own sleep timing feels in real life.
The Lark-Owl Chronotype Indicator (LOCI) and the Munich Chronotype Questionnaire (MCTQ) were designed using a quantitative approach, which encourages recording concrete bedtimes, wake times, and mid-sleep times when you review your own logs.
A step-by-step record check you can try
- Pick one validated questionnaire such as the Morningness–Eveningness Questionnaire (MEQ) or the Composite Scale of Morningness (CSM), complete it once, and write down the date and whatever overall score or category it provides.
- On several free days when you do not have work or school obligations, record your sleep onset time and your wake time, then calculate the mid-sleep time for each of those days as a personal sleep-based chronotype marker, since mid-sleep on free days may be the best marker for sleep-based assessments of chronotype.
- Keep a short daily log of how rigid or flexible your sleep timing feels and how easy it is to overcome drowsiness, using the CTI description as a guide to the dimensions of rigidity/flexibility and ability to overcome drowsiness that researchers have assessed.
- For several days, note approximate times for major light exposure, meals, social activities, and work or school, to observe how these zeitgebers might line up with your recorded sleep timing, since light, feeding, social behavior, and work and school schedules are important environmental cues in gene–environment interactions regulating chronotypes.
- If you have access to sleep timing records from different ages in your life or from different age groups in your household, place them side by side to look for the developmental pattern in which pre-pubescent children tend to prefer an advanced sleep period, adolescents prefer a delayed sleep period, and many elderly prefer an advanced sleep period.
Putting it all together
Chronotype describes when you tend to sleep within a 24-hour period and can be located along a morningness–eveningness range rather than in a single rigid category.
Research tools such as the Morningness–Eveningness Questionnaire (MEQ), the Composite Scale of Morningness (CSM), the Circadian Type Inventory (CTI), the Lark-Owl Chronotype Indicator (LOCI), and the Munich Chronotype Questionnaire (MCTQ) show that even simple information like typical sleep timing, mid-sleep on free days, and perceived flexibility can be turned into structured data about your own chronotype.
If you want to apply this, one practical learning task to try is to keep a short chart for several free days where you write down your sleep onset, wake time, calculated mid-sleep, main daily zeitgebers, and a brief note on how rigid or flexible your sleep felt that day, then look back after several entries to see whether your own pattern looks more advanced, more delayed, or somewhere in the middle.
This article is general health information and is not a substitute for medical diagnosis or treatment. Consult a healthcare professional if you have concerns.