title: Exploration of Circadian Rhythms in Patients with Bilateral Vestibular Loss.
abstract: BACKGROUND
  New insights have expanded the influence of the vestibular system to the regulation of circadian rhythmicity. Indeed, hypergravity or bilateral vestibular loss (BVL) in rodents causes a disruption in their daily rhythmicity for several days. The vestibular system thus influences hypothalamic regulation of circadian rhythms on Earth, which raises the question of whether daily rhythms might be altered due to vestibular pathology in humans. The aim of this study was to evaluate human circadian rhythmicity in people presenting a total bilateral vestibular loss (BVL) in comparison with control participants.
  
  
  RESULTS
  Nine patients presenting a total idiopathic BVL and 8 healthy participants were compared. Their rest-activity cycle was recorded by actigraphy at home over 2 weeks. The daily rhythm of temperature was continuously recorded using a telemetric device and salivary cortisol was recorded every 3 hours from 6:00AM to 9:00PM over 24 hours. BVL patients displayed a similar rest activity cycle during the day to control participants but had higher nocturnal actigraphy, mainly during weekdays. Sleep efficiency was reduced in patients compared to control participants. Patients had a marked temperature rhythm but with a significant phase advance (73 min) and a higher variability of the acrophase (from 2:24 PM to 9:25 PM) with no correlation to rest-activity cycle, contrary to healthy participants. Salivary cortisol levels were higher in patients compared to healthy people at any time of day.
  
  
  CONCLUSIONS
  We observed a marked circadian rhythmicity of temperature in patients with BVL, probably due to the influence of the light dark cycle. However, the lack of synchronization between the temperature and rest-activity cycle supports the hypothesis that the vestibular inputs are salient input to the circadian clock that enhance the stabilization and precision of both external and internal entrainment.
authors.affiliation: UNICAEN, COMETE, 14032 Caen, France.|INSERM, U1075, 14032 Caen, France.|Normandie Universite, Caen, France.
authors.forename: Tristan
authors.initials: T
authors.lastname: Martin
authors.affiliation: UNICAEN, COMETE, 14032 Caen, France.|INSERM, U1075, 14032 Caen, France.|Normandie Universite, Caen, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Moussay
authors.affiliation: Theoretical Biology and Biophysics, Group T-6, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America.|Institut für Mathematik und Informatik, Universität Greifswald, Walther-Rathenau-Straße 47, 17487 Greifswald, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Bulla
authors.affiliation: Department of Mathematics, University of Bergen, P.O. Box 7800, 5020 Bergen, Norway.
authors.forename: Jan
authors.initials: J
authors.lastname: Bulla
authors.affiliation: Centre d'explorations fonctionnelles oto-neurologiques, 10 rue Falguière, 75 015 Paris, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Toupet
authors.affiliation: Normandie Universite, Caen, France.|CHU de Caen, Service des Explorations Fonctionnelles, 14000 Caen, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Etard
authors.affiliation: UNICAEN, COMETE, 14032 Caen, France.|INSERM, U1075, 14032 Caen, France.|Normandie Universite, Caen, France.|CHU de Caen, Service des Explorations Fonctionnelles, 14000 Caen, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Denise
authors.affiliation: UNICAEN, COMETE, 14032 Caen, France.|INSERM, U1075, 14032 Caen, France.|Normandie Universite, Caen, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Davenne
authors.affiliation: UNICAEN, COMETE, 14032 Caen, France.|INSERM, U1075, 14032 Caen, France.|Normandie Universite, Caen, France.|CHU de Caen, Laboratoire de pharmacologie-toxicologie, 14000 Caen, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Coquerel
authors.affiliation: UNICAEN, COMETE, 14032 Caen, France.|INSERM, U1075, 14032 Caen, France.|Normandie Universite, Caen, France.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Quarck
mesh_terms: D000204:Activity Cycles; D000328:Adult; D000368:Aged; D000071699:Bilateral Vestibulopathy / Q000378:metabolism / Q000503:physiopathology*; D001831:Body Temperature; D016022:Case-Control Studies; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D017440:Photoperiod; D012463:Saliva / Q000378:metabolism; D012890:Sleep
chemical_list: D006854:Hydrocortisone