ABSTRACT
<p><b>OBJECTIVE</b>To observe the habituation of seasickness in non marine subjects during a long voyage.</p><p><b>METHODS</b>A crew of 106 staffs of the Hospital Ship Ark Peace was included in this study. There were 59 male and 47 female with an age ranged from 23 to 53 years (mean 37.2 years). They all took part in the Mission Harmony 2011 for medical service in four countries around the Caribbean Sea. Questionnaires and visual analogue scales (VAS) were used to investigate the prevalence and degree of the seasickness in different periods.</p><p><b>RESULTS</b>The prevalence of seasickness was 72.64% in the initial period of voyage. The prevalence and degree of seasickness in female and in staff with motion sickness history were higher and more severe than that in male and in staff without motion sickness history(P < 0.05). After two weeks, the prevalence and degree of seasickness decreased, which meant habituation of seasickness occurred. With the voyage going longer, the prevalence and degree of seasickness were further decreased, but the severe sea condition make the prevalence and degree of seasickness worse. The rate of habituation of seasickness was 62.33%, and the habituation rate of seasickness in male (76.92%) was higher than that in female (47.37%) (χ(2) = 7.161, P = 0.007).</p><p><b>CONCLUSIONS</b>The habituation of the seasickness occurred after two weeks in a long voyage. Male are easier to get habituation of seasickness than female. The severe sea condition influences the prevalence and degree of seasickness.</p>