Abstract
BackgroundNew 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.Methodology and Principal FindingsNine 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.ConclusionWe 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.
Highlights
Locomotion and postural regulation arise from a complex system where somatosensory, vestibular, and visual information is interrelated [1]
Vestibular System and Circadian Rhythms 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
In patients suffering from bilateral vestibular loss (BVL), clear disruptions of angular and linear VOR are present in low frequency movements [7,8,9], leading to oscillopsia and blurred vision
Summary
Locomotion and postural regulation arise from a complex system where somatosensory, vestibular, and visual information is interrelated [1]. Disturbance or suppression of any of these processes leads to postural imbalance and impaired locomotion [2,3,4]. In patients suffering from bilateral vestibular loss (BVL), clear disruptions of angular and linear VOR are present in low frequency movements [7,8,9], leading to oscillopsia and blurred vision. New insights have expanded the influence of the vestibular system to the regulation of circadian rhythmicity. Hypergravity or bilateral vestibular loss (BVL) in rodents causes a disruption in their daily rhythmicity for several days. 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
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