chronotyping

Chronotyping is the process of classifying an individual according to their circadian timing and preferred daily activity pattern. In sleep and circadian research, chronotypes describe a person’s propensity to be active and alert at particular times of day, typically on a spectrum from morning-type to evening-type, with intermediate types in between.

Assessment methods include self-report questionnaires such as the Morningness-Eveningness Questionnaire (MEQ) and the Munich Chronotype Questionnaire (MCTQ). Objective measures include sleep logs, actigraphy, and the timing of endogenous markers like dim light melatonin onset (DLMO).

Applications: Chronotyping informs clinical management of circadian rhythm disorders, supports personalized scheduling in workplaces and schools, and is used in research on sleep, mood, metabolism, and performance. For example, evening-types may benefit from exposure to morning light and adjusted work shifts; morning-types may perform best earlier in the day.

Biological basis: Chronotype arises from the timing of the internal circadian clock in the suprachiasmatic nucleus, interacting with homeostatic sleep pressure and environmental cues such as light. Genetics, age, and sex play roles; chronotype tends to shift toward morningness with age and varies across populations.

Limitations: Chronotype is best viewed as a spectrum rather than discrete categories, and measurement can be influenced by lifestyle, sleep debt, and cultural factors. Chronotyping is one tool among broader chronobiology research and should be integrated with other assessments for clinical or occupational decisions.