Correlation Between Heart Rate and the Severity of Motion Sickness Caused by Optokinetic Stimulation

Heart rate has been reported to increase during nausea and has therefore been used as an indicator of motion sickness. However, the relationship between heart rate and subjective ratings of motion sickness has received little attention, and the autonomic origins of any increase in heart rate during motion sickness are unknown. Spectral analysis of heart rate variability can quantify the degree of sympathetic and parasympathetic stimulation of the heart, as reflected by the low frequency (LF) power and high frequency (HF) power components, and the ratio of LF:HF power (“autonomic balance”). This experiment investigated changes in heart rate and heart rate variability prior to and during the development of nausea. Forty subjects (20 male, 20 female) sat within an optokinetic drum (a visual stimulus) rotating at 5 rpm for a maximum of 32 minutes. Heart rates, measures of heart rate variability, and ratings of sickness were recorded during a resting pre-exposure period and during optokinetic stimulation. Heart rates increased significantly with increasing subjective ratings of sickness (P < .001). This appeared to be attributable to a net increase in sympathetic stimulation of the heart, (P < .05). Sickness ratings were greater for females than males (P = .09), consistent with a significantly greater history of motion sickness reported by females than males over the previous 12 months (P < .02). The findings suggest that a simple measure of heart rate may be a useful indicator of small changes in the degree of sickness that can be of interest in motion sickness research.