LAUSR

Background Although depression and motion sickness are prevalent in military personnel and seafarers, the association between depression and seasickness has been not yet elucidated. We aimed to evaluate the relationship of depression with initial susceptibility and adaptation to seasickness amongst military seafarers. Methods This retrospective cohort enrolled Navy seafarers who started seafaring between 2017 and 2019. Three groups were established according to the Beck Depression Inventory (BDI) score: no depression (BDI score of 0), minimal depression (BDI score 1–9), and mild-to-moderate depression (BDI score 10–29). The occurrence of seasickness requiring treatment was observed as the prescription of medication for the first 30 distant seafaring days. Considering adjustment period, the two different outcomes were defined. The susceptibility to seasickness was evaluated via at least one day suffered from seasickness requiring treatment during the early period (the first 5 seafaring days), and adaptation ability to seasickness was defined by more than 10% of the ratio, calculated days suffered from seasickness requiring treatment/days of seafaring during the late period (the 6–30th seafaring days). Binary logistic regression was further evaluated to estimate the odds of BDI groups and BDI score adjusted for age and workplace whether outside visual perception was possible. Results Among the 185 recruits, 179 participants (97%) sailed for more than 5 days were included in the study. Of the participants, 36% was susceptible to seasickness in the early and 17% was poorly adapted to seasickness in the late period. Multivariable model revealed that mild-to-moderate depression had elevated risk of poor adaptation (odds ratio [OR], 4.63; 95% confidence interval [CI], 1.31–16.98) whereas the results were not statistically significant for susceptibility to seasickness in the early period BDI score was independently associated with increased odds of poor adaptation (OR, 1.10; 95% CI, 1.04–1.18). Conclusion The present study suggests that depression is associated with poor adaptation to seasickness in Navy seafarers. Depression screening tool might be helpful for providing preventable strategies for population at risk.