Motion sickness susceptibility fluctuates through the menstrual cycle

Background: Motion sickness is a common and potentially debilitating condition that characteristically occurs in situations of conflicting sensory input. While the precise stimuli that give rise to this trait are increasingly well characterized, the underlying determinants of individual susceptibility to motion sickness remain unclear. This study uses a classical twin design to assess the influence of genetic and environmental factors. Methods: A postal survey was conducted in an age-matched sample of 3652 monozygotic (MZ) and dizygotic (DZ) adult female twins selected from the TwinsUK Registry. Study participants were asked to complete items from a validated questionnaire relating to their lifetime susceptibility to motion sickness. The relative contribution of genetic and environmental factors to motion sickness susceptibility was assessed using variance components analysis. Results: The response rate to the questionnaire was 78%. Approximately 40% of respondents reported at least moderate susceptibility to motion sickness. The pattern of responses among twins indicated a significant genetic contribution with heritability for a motion sickness factor score estimated as 57% (95% CI: 51%, 63%). The heritability of recalled motion sickness was at its highest in childhood (70% [59%, 80%]) and declined through puberty and the early adult years. Discussion and Conclusions: The findings highlight the importance of genetic factors in determining an individual's underlying propensity to motion sickness and should stimulate the search for specific susceptibility genes