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Human Circadian Phenotyping and Diurnal Performance Testing in the Real World
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Published on: April 7, 2020

Does the chronotype classification need to be updated? Preliminary findings.

Bruno Jacson Martynhak1, Fernando Mazzilli Louzada, Mário Pedrazzoli

  • 1Department of Pharmacology, Federal University of Paraná, Curitiba, Brazil. brunojm@ymail.com

Chronobiology International
|July 27, 2010
PubMed
Summary

A novel algorithm identifies a "bimodal" chronotype in individuals with mixed morning and evening sleep preferences. This finding may necessitate an update to current sleep-wake cycle classifications.

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Area of Science:

  • Chronobiology
  • Sleep Science
  • Behavioral Neuroscience

Background:

  • Chronotype classification traditionally relies on the Morningness-Eveningness Questionnaire (MEQ).
  • MEQ assumes intermediate scores reflect a blend of morning and evening tendencies.
  • A subset of individuals exhibits mixed response patterns, challenging this assumption.

Purpose of the Study:

  • To develop and validate a method for identifying a "bimodal" chronotype.
  • To investigate individuals who exhibit both morning and evening-type responses on the MEQ.
  • To propose an update to chronotype classification if a bimodal pattern is confirmed.

Main Methods:

  • Defined "morning-type" and "evening-type" answers as A(4) and A(1), respectively.
  • Defined intermediate answers as A(2) and A(3).
  • Applied a Bimodality Index algorithm: (Sigma A(1) x Sigma A(4))² - (Sigma A(2) x Sigma A(3))².
  • Classified individuals with positive Bimodality Index scores as "neither-types" exhibiting bimodal tendencies.

Main Results:

  • A novel algorithm was developed to quantify chronotype bimodality.
  • Individuals with mixed response patterns were identified as potentially "bimodal" chronotypes.
  • The proposed method offers a quantitative approach to identifying this distinct sleep pattern.

Conclusions:

  • The existence of a bimodal chronotype, characterized by mixed morning and evening preferences, is proposed.
  • This classification challenges the traditional MEQ-based continuum.
  • Further validation with objective data is required to support an update in chronotype classification.