Motion Exposure, Cognitive Impairment, and Risk Factors for Mal de Débarquement Syndrome.

OBJECTIVE

Determine whether shipboard motion variability relates to simulator‑sickness symptoms, Mal de Débarquement syndrome (MdDS) features, and cognition, and whether migraine or motion‑sickness history modify these vestibular effects.

STUDY

DESIGN

Prospective observational cohort.

SETTING

USNS Mercy (T‑AH 19) during Pacific Partnership 2024.

METHODS

38 Active‑Duty personnel were tested at baseline (land), after California-Hawaii (CA-HI; rougher), and after Chuuk-Hawaii (CHUUK-HI; calmer). A centrally mounted, inertial measurement unit (IMU) yielded per‑minute standard deviation of linear‑acceleration magnitude (IMU SD).

OUTCOMES: Simulator Sickness Questionnaire (SSQ); MdDS calculator mapped to Bárány criteria; Rey-Osterrieth Complex Figure (ROCF); Symbol Digit Modalities Test (SDMT); Stroop Test; linear mixed-effects model using voyage leg and IMU SD as predictors of symptom outcomes and adjusted for migraine and motion‑sickness history.

RESULTS

IMU SD was higher on CA-HI. SSQ totals were higher on CA-HI and increased with IMU SD. MdDS criteria counts, and cases were similar between legs; Migraine Disability Assessment Score (MIDAS) was positively associated with MdDS criterion burden, but not with SSQ. ROCF showed slower copy/recall and lower recall accuracy on CA-HI; SDMT and Stroop errors were largely unchanged. There were no statistical differences based on migraine or motion‑sickness history, but analyses were limited by small subgroup sizes.

CONCLUSION

Rougher sea states (greater IMU variability) were linked to higher acute symptom burden and specific visuospatial memory impairments. The incidence of persistent MdDS did not differ by leg. IMU‑informed monitoring with brief, targeted cognitive tests may support future planning and post‑voyage screening to identify at-risk individuals.