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Updated: May 12, 2026
10:16
Human Circadian Phenotyping and Diurnal Performance Testing in the Real World
Published on: April 7, 2020
Sleepiness phenomics: modeling individual differences in subjective sleepiness profiles.
Olivier Mairesse1, Elke De Valck2, Stijn Quanten3
1Vrije Universiteit Brussel, Experimental and Applied Psychology, Belgium; Royal Military Academy, Vital Signs and Performance, Belgium; Brugmann University Hospital, Center for Sleep and Biological Rhythms, Belgium.
Summary
This study reveals three key components explaining 80% of individual differences in sleepiness during sustained wakefulness. These components relate to sleep homeostasis, circadian amplitude, and diurnal preference, offering insights into sleep regulation.
Area of Science:
- Sleep science
- Chronobiology
- Human physiology
Background:
- Individual differences in sleepiness impact daily functioning and health.
- Understanding the physiological basis of these differences is crucial for targeted interventions.
- Previous research often focuses on group averages, overlooking inter-individual variability.
Purpose of the Study:
- To investigate individual differences in subjective sleepiness profiles during prolonged wakefulness.
- To identify underlying physiological factors contributing to these variations.
- To explore the relationship between sleepiness, sleep homeostasis, circadian rhythms, and diurnal preference.
Main Methods:
- Utilized a modified constant routine protocol with 36 hours of sustained wakefulness.
- Collected subjective sleepiness ratings using visual analogue scales every 2 hours.
- Assessed circadian rhythmicity via salivary cortisol measurements.
- Analyzed sleepiness data using functional principal component analysis (fPCA).
Main Results:
- Three functional components accounted for approximately 80% of the variance in sleepiness profiles.
- Component 1 (50.28% variance) linked to sleep homeostasis, habitual sleep duration, and slow wave activity.
- Component 2 (18.40% variance) associated with circadian amplitude and salivary cortisol amplitude.
- Component 3 (10.09% variance) related to diurnal preference, morning sleepiness, and later cortisol peaks.
Conclusions:
- Identified three distinct components reflecting tonic sleepiness, circadian amplitude, and diurnal preference.
- Suggests that inter-individual variability in sleepiness arises from a complex interplay of physiological parameters.
- Highlights the potential of fPCA for uncovering physiological processes and defining sleepiness phenotypes.
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