title: The role of the parasympathetic nervous system in visually induced motion sickness: systematic review and meta-analysis.
abstract: The parasympathetic nervous system (PNS) has been implicated in the development of visually induced motion sickness. The objective of this study was to perform a systematic review and meta-analysis of the effect of visually induced motion sickness on validated parameters of PNS tone. Methods followed PRISMA recommendations. Controlled trials reporting validated measures of PNS tone in visually induced motion sickness in healthy adults were included. One reviewer performed the screening of articles and data extraction, and two reviewers independently performed methodological evaluation. Data were synthesised using standardised mean differences (SMDs) for all relevant outcomes using a random-effects model. Publication bias was assessed via funnel plots and Egger's test. The search strategy identified seven citations comprising 237 healthy individuals. The mean quality score was 4/10 (range 3-7). There was no difference between baseline PNS tone between individuals who developed visually induced motion sickness and those that did not. Visually induced motion sickness (VIMS)-sensitive individuals had a reduction in PNS tone, following exposure to the stimulus (mean weighted SMD = -0.45, 95% confidence interval -0.64 to -0.27, Z = -4.8, p < 0.0001). There was no evidence of heterogeneity or publication bias. These data suggest that baseline PNS parameters do not provide a useful measure of predicting the probability of developing visually induced motion sickness. However, a fall in PNS tone, as indicated by cardiac activity, is characteristic in sensitive individuals. Further work is needed to characterise these responses in clinical populations, in conjunction with improvements and standardisation in study design.
authors.affiliation: Neurogastroenterology Group, Blizard Institute of Cell and Molecular Science, Wingate Institute of Neurogastroenterology, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, 26 Ashfield Street, London, E1 2AJ, UK, a.farmer@qmul.ac.uk.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Farmer
authors.forename: Yasser
authors.initials: Y
authors.lastname: Al Omran
authors.forename: Qasim
authors.initials: Q
authors.lastname: Aziz
authors.forename: Paul L
authors.initials: PL
authors.lastname: Andrews
mesh_terms: D006801:Humans; D009041:Motion Sickness / Q000209:etiology* / Q000473:pathology*; D010275:Parasympathetic Nervous System / Q000503:physiopathology*; D010775:Photic Stimulation / Q000009:adverse effects*