Towards quantitative sleepiness phenotypes.

Olivier Mairesse, Elke De Valck, Aisha Cortoos, Daniel Neu, Nathalie Pattyn, Joeri Hofmans

Onderzoeksoutput: Meeting abstract (Journal)


Objectives: Subjective sleepiness is likely the organism's first indication of the detrimental effects of prolonging wakefulness. As individuals largely differ in their vulnerability to sleep loss, accounting for individual differences in subjective sleepiness is of crucial importance when considering safety critical operations. The purpose of this study is to precisely quantify the determinants of inter-individual variability in daytime sleepiness to capture its phenotypic richness.
Methods: 23 volunteers (11 females; M age=30.41, SD= 10.26) enrolled in a 36hr constant routine. Sleepiness was assessed 2-hourly by means of VASs and of the Karolinska Drowsiness Test. Circadian rhythmicity was assessed through salivary cortisol. Subjective sleepiness data were subjected to a functional principal component analysis (fPCA).
Results: Approximately 80% of the total variance is accounted for by three functional components: component S (50.28%), component C (18.40%) and component D (10.09%). High (low) scores on component S raise (lower) the mean sleepiness profile. Individuals with high (low) scores on component C display more (less) rhythmic variability in their sleepiness profiles, as characterized by a higher (lower) peak-to-through amplitude. Participants with high (low) scores on component D show higher (lower) than average levels of subjective sleepiness during morning hours and a buildup of wake effort occurring later (earlier) than low (high) scorers. Component S scores were related to self-reported habitual sleep times (r= .58, p<.05) and mean EEG delta power during the KDT (r= .46, p<.05). Participants with higher (lower) than average component C scores showed a significant higher (lower) amplitude in cortisol profiles (t(20)= -2.164, p<.05). Finally, the circadian phase of cortisol occurs significantly later (earlier) in participants with higher (lower) than average scores on component D (t(20)= 1.77, p Conclusion: It is concluded that component S represents the responsiveness of the sleep homeostat and its initial level, whereas component C is related to circadian strength and component D to diurnal preference. Our results show that the major modes of variations in sleepiness profiles mirror well-known sleep regulatory processes and allow for the specification of sleepiness phenotypes on a precise quantitative basis. These results have promising implications for further research relating sleepiness phenotypes to genetic factors.
Originele taal-2English
Pagina's (van-tot)334-335
Aantal pagina's2
TijdschriftJournal of Sleep Research
Nummer van het tijdschrift1
StatusPublished - 2012
EvenementUnknown -
Duur: 1 jan 2012 → …


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