Discussion
nausea and vomiting, MSAQ, Nausea
MOTION SICKNESS, DISEASE
Evaluation of the construct validity of the MSSS was motivated by the desire for a reliable diagnostic instrument to assess the severity of motion sickness with the following elements: measurement of core symptoms, brevity, clarity of scale items for undemanding completion, potential for repeated and rapid assessment of acute motion sickness severity during stimulus presentation (including when the respondent is distressed), and scalability. To evaluate the MSSS with attention to these elements, the scale was compared to two validated assessments: a brief questionnaire (PGI-S) used as an index of global illness severity, and a comprehensive questionnaire (MSAQ) used as an assessment of the multiple dimensions of motion sickness. This analysis of the construct validity of the MSSS provides evidence that the MSSS correlates strongly with validated and widely used questionnaires and is therefore a valid instrument for the assessment of motion sickness.Scores on the MSSS correlated very highly with scores on the PGI-S, and sufficient differentiation is supported by the within-group ANOVA demonstrating significant increases in mean MSSS scores with increasing PGI-S severity level. The order and shape of the PGI-S ECDFs reveal that grouped MSSS score distributions indicate that higher PGI-S severity levels are associated with higher MSSS scores, and lower PGI-S severity levels are associated with lower MSSS scores. This analysis suggests that the MSSS accurately measures motion sickness severity progression from no symptoms to stomach awareness and eventually to severe nausea and vomiting [Similarly, scores on the MSSS correlated highly with scores on the MSAQ. The high degree of association of scores between the questionnaires supports the construct validity of the MSSS based on the MSAQ, which was designed to capture the highly variable symptom profiles of motion sickness and validated against two widely used motion sickness severity assessment instruments: the Pensacola Diagnostic Index and Nausea Profile [Together, the findings of this paper in evaluating the 7-item MSSS and those of Reuten Of note, the MSAQ was validated based on motion sickness ratings from 21 students following exposure to a rotating optokinetic drum [This evaluation of the validity of the MSSS was performed on data collected in a single study in which participants with a history of motion sickness were exposed to different sea conditions and randomized to take Tradipitant or placebo as part of the Motion Sifnos Study, with the primary analysis focused on participants without antiemetic treatment. While these environmental and interventional variables may increase the variability in questionnaire scoring as potential confounders, results from the exploratory analysis further support the MSSS for assessing motion sickness. The robustness of scores with the inclusion of these variables indicates that the utility of the MSSS may extend across populations, interventions, and stimuli.The findings reported in this study establish the MSSS as a highly performing instrument for the assessment of motion sickness designed for use during stimulus presentation, presenting motion sickness researchers with a valuable symptom-screening instrument comparable to the recently evaluated MISC. Further research using the MSSS for repeated assessment of motion sickness severity in larger populations with exposure to variable provocative stimuli will further inform its utility. Going forward, the MSSS can serve as a valuable instrument—in both clinical and research settings—that can be administered to assess motion sickness severity and reflect global state of disease.We thank the participants of the Motion Sifnos Study for their commitment to helping us in find a new treatment for motion sickness. We thank Dr. Daniel Norman MD and the site study staff. We thank the nautical staff involved in the boat travel assessment. We thank our colleagues at Vanda Pharmaceuticals for their support in conducting the study including: Austin Anderson, Jane Miglo, Maggie Gibson, Suzanne Quebbeman, Xian Cui, Patrick Collins, Grace Li, Zibo Wang, and Katerina Polymeropoulos.