Predisposition to Seasickness: Who Is at Risk?

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Seasickness (aka motion sickness) can be a surprisingly unpleasant experience, with a few people on a crowded boat feeling woozy, nauseated, dizzy, or just plain miserable, while the majority remains unfazed. It can interfere with enjoyment of warm weather leisure activities, including riding on a sailboat, taking a cruise, and even taking a ferry to reach an island destination. A ferry ride to visit the Statue of Liberty, for example-one of the most beloved and visited attractions in the world-can make some people too ill to appreciae the sought-after destination.

In general, some are more prone to seasickness than others. But most people who get seasick do not necessary feel miserable every time they take a boat ride, which is why the feeling can be unforeseen for those who had taken boat excursions without discomfort in the past. Some characteristics associated with a predisposition to seasickness can partially explain why individuals are more prone to it than others.

Genetics

Twins studies are considered among the best methods of assessing genetic predisposition to complex physiological traits. A British study that included 3652 pairs of twins showed that monozygotic twins had a stronger tendency to share the tendency of seasickness than dizygotic twins, pointing to a genetic component of the condition.¹

However, as monozygotic twins entered adolescence and adult years, there was a divergence in their predisposition to seasickness, suggesting that environmental factors or personal habits could play a role in the experience of seasickness as well.

Physiology

Physiologic measures are also associated with seasickness. A Japanese study evaluated volunteers on an Antarctic voyage.² The volunteers had their end-tidal CO₂ measured, and those with a low end-tidal CO₂ were more likely to report a feeling seasick.

Expiratory CO₂ level can be related to an individual’s natural respiratory pattern, respiratory efficiency, or physical fitness. The researchers suggested that slow, deep breathing, which raised CO₂, was a subconscious behavioral method used by some of the volunteers to avoid seasickness. This is interesting as a cause and effect observation, because it suggests that individuals who are prone to seasickness could learn breathing methods to prevent or decrease their symptoms.

Postural stability

Another feature that plays a role in seasickness is postural stability. A study of men and women in Minnesota showed some very interesting conclusions about postural differences between men and women and the role it may play in seasickness.³ Although some studies have demonstrated a correlation between postural instability and seasickness and others have differentiated instability between men and women, this study combined all of these factors.

It turned out that when they were on a sea vessel, the female participants were less able than men to regain their postural stability and were more prone to seasickness than men. While it is suggested that men’s higher BMI could provide an advantage in postural stability, it also opens the door to possible remedies for both men and women in preventing seasickness, including exercises that increase postural stability, such as yoga.

Seasickness can be difficult to manage once symptoms begin. However, there are some physiological characteristics that can be modified to help prevent seasickness from occurring.

References:

1. Reavley CM, Golding JF, Cherkas LF, et al. Genetic influences on motion sickness susceptibility in adult women: a classical twin study. Aviat Space Environ Med. 2006;77:1148-1152.

2. Hasegawa T, Oe H, Taki M, et al. End-tidal CO2 relates to seasickness susceptibility: A study in Antarctic voyages. Auris Nasus Larynx. 2017;44:534-539.

3. Koslucher F, Haaland E, Stoffregen TA. Sex differences in visual performance and postural sway precede sex differences in visually induced motion sickness. Exp Brain Res. 2016;234:313-22.