title: Interindividual differences in the dynamics of the homeostatic process are trait-like and distinct for sleep versus wakefulness.
abstract: The sleep homeostatic Process S reflects the build-up of sleep pressure during waking and its dissipation during sleep. Process S is modelled as a saturating exponential function during waking and a decreasing exponential function during sleep. Slow wave activity is a physiological marker for non-rapid eye movement (non-REM) sleep intensity and serves as an index of Process S. There is considerable interindividual variability in the sleep homeostatic responses to sleep and sleep deprivation. The aim of this study was to investigate whether interindividual differences in Process S are trait-like. Polysomnographic recordings of 8 nights (12-h sleep opportunities, 22:00-10:00 hours) interspersed with three 36-h periods of sustained wakefulness were performed in 11 healthy young adults. Empirical mean slow wave activity per non-REM sleep episode at episode mid-points were used for parameter estimation. Parameters of Process S were estimated using different combinations of consecutive sleep recordings, resulting in two to three sets of parameters per subject. Intraclass correlation coefficients were calculated to assess whether the parameters were stable across the study protocol and they showed trait-like variability among individuals. We found that the group-average time constants of the build-up and dissipation of Process S were 19.2 and 2.7 h, respectively. Intraclass correlation coefficients ranged from 0.48 to 0.56, which reflects moderate trait variability. The time constants of the build-up and dissipation varied independently among subjects, indicating two distinct traits. We conclude that interindividual differences in the parameters of the dynamics of the sleep homeostatic Process S are trait-like.
authors.affiliation: Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.|University Hospital of Child and Adolescent Psychiatry and Psychotherapy, University of Bern, Bern, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Rusterholz
authors.affiliation: Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.|University Hospital of Child and Adolescent Psychiatry and Psychotherapy, University of Bern, Bern, Switzerland.|Department of Psychiatry and Human Behavior, The Alpert Medical School of Brown University, Providence, RI, USA.
authors.forename: Leila
authors.initials: L
authors.lastname: Tarokh
authors.affiliation: Sleep and Performance Research Center, Washington State University, Spokane, WA, USA.|Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, USA.
authors.forename: Hans P A
authors.identifier: 0000-0002-4678-2971
authors.initials: HP
authors.lastname: Van Dongen
authors.affiliation: Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.|The KEY Institute for Brain-Mind Research, Department of Psychiatry, Psychotherapy and Psychosomatics, University Hospital of Psychiatry, Zurich, Switzerland.|Zurich Center for Interdisciplinary Sleep Research, University of Zurich, Zurich, Switzerland.|Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.|Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland.
authors.forename: Peter
authors.identifier: 0000-0002-0208-3511
authors.initials: P
authors.lastname: Achermann
mesh_terms: D000328:Adult; D004569:Electroencephalography; D005260:Female; D064368:Healthy Volunteers; D006706:Homeostasis; D006801:Humans; D007206:Individuality; D008297:Male; D010641:Phenotype; D012890:Sleep / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology*
keywords: ICC; mathematical modeling; multiple recordings; phenotype; sleep/wake regulation; variance components