Abstract
Background The risk of traumatic brain injury (TBI) and comorbid posttraumatic dizziness is elevated in military operational environments. Sleep deprivation is known to affect a service member's performance while deployed, although little is known about its effects on vestibular function. Recent findings suggest that moderate acceleration step rotational stimuli may elicit a heightened angular vestibulo-ocular reflex (aVOR) response relative to low-frequency sinusoidal stimuli after 26 hours of sleep deprivation. There is concern that a sleep deprivation–mediated elevation in aVOR function could confound detection of comorbid vestibular pathology in service members with TBI. The term “dynamic visual acuity” (DVA) refers to an individual's ability to see clearly during head movement and is a behavioral measure of aVOR function. The Dynamic Visual Acuity Test (DVAT) assesses gaze instability by measuring the difference between head-stationary and head-moving visual acuity.
Objective The purpose of this study was to investigate the effects of 26 hours of sleep deprivation on DVA as a surrogate for aVOR function.
Design This observational study utilized a repeated-measures design.
Methods Twenty soldiers with no history of vestibular insult or head trauma were assessed by means of the DVAT at angular head velocities of 120 to 180°/s. Active and passive yaw and pitch impulses were obtained before and after sleep deprivation.
Results Yaw DVA remained unchanged as the result of sleep deprivation. Active pitch DVA diminished by −0.005 LogMAR (down) and −0.055 LogMAR (up); passive pitch DVA was degraded by −0.06 LogMAR (down) and −0.045 LogMAR (up).
Limitations Sample homogeneity largely confounded accurate assessment of test-retest reliability in this study, resulting in intraclass correlation coefficients lower than those previously reported.
Conclusions Dynamic visual acuity testing in soldiers who are healthy revealed no change in gaze stability after rapid yaw impulses and subclinical changes in pitch DVA after sleep deprivation. Findings suggest that DVA is not affected by short-term sleep deprivation under clinical conditions.
Footnotes
Dr Scherer provided concept/idea/research design and project management. All authors provided writing. Dr Scherer and Mr Claro provided data collection and analysis. Dr Heaton provided study participants, facilities/equipment, and consultation (including review of manuscript before submission). The authors thank Elisabeth Kryskow and Alexis Maule in support of this research; Caitlin Dillon for her assistance with figure preparation; and Dr Emily Blood and Dr Steve Allison for insightful recommendations and technical expertise in the statistical treatment of the data.
This study was approved by the Institutional Review Board of the US Army Research Institute of Environmental Medicine.
A platform presentation of this research was given at the Combined Sections Meeting (Neurology Section) of the American Physical Therapy Association; February 10, 2012; Chicago, Illinois.
This work was supported by Congressionally Directed Medical Research Programs (CDMRP) through an Advanced Technology Award (W81XWH-08-2-0,177) to Jamshid Ghajar and by the US Army Medical Research and Materiel Command (USAMRMC) through W81XWH-08-1-0,021 to Dr Heaton.
The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.
- Received March 30, 2012.
- Accepted November 8, 2012.
- © 2013 American Physical Therapy Association
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