Response to queries and comments on Seasickness

Professor Hugh Grantham

Professor Hugh Grantham’s blog post on Seasickness has sparked lively discussions and thoughtful comments in the boating and sailing communities where it was shared. Rather than replying to each comment individually, Hugh has written a short article addressing all the questions and points raised by our enthusiastic readers. It’s an informative and engaging read! We'd love to hear your thoughts.

By Professor Hugh Grantham

Many people have responded and shared their thoughts on seasickness.

Starting with the abstract on motion sickness and space travel, it proposed a couple of possible theories—one of which was the sensory conflict caused by unusual or changing balance inputs from the middle ear. The most telling comment, however, was that further research is needed.

Sharing stories and theories among a wide group of people is, in itself, a form of research: exchanging experiences and beliefs and looking for common themes.

Looking at the responses so far, it seems that concentrating and forcing the mind to focus on other things—like steering—is reported as helpful. We all agree that stopping the motion by going ashore and sitting under a tree is the ultimate cure.

It's interesting that the idea of blocking one ear came up more than once. Why this would be helpful is hard to explain from a scientific point of view. The semicircular canals in the middle ear—responsible for sending positional input to the brain—have nothing to do with the hearing function of the ears, and would not be affected by altering the noise or vibration reaching the eardrum. You have to wonder whether this is simply another way to divert focus, similar to the way pressure points, magnets, and similar approaches might work.

There is still some support for old-fashioned sedating antihistamines. This is likely because they have worked for individuals in the past, and those people continue to trust in them. In my opinion, although they can be effective, the side effects are not acceptable if you can achieve the same benefit by safer means. Sedation at sea renders a person unfit for duty—and worse, there's the risk of inducing psychosis or other acute neurological effects. As I said in the original post, these should be reserved as a last resort when you can accept and manage the side effects.

Another interesting thread is that people adapt and “get their sea legs.” This suggests an adaptation process is taking place. The evidence of this, and the variation in severity and duration between individuals, supports the idea that seasickness is related to how the brain interprets sensory inputs and that our brains can adapt to differing inputs.

There are two recurring themes: first, the importance of doing something early as a preventative or nip it in the bud; and second, that actions which don’t make strict logical sense still seem to help—particularly if the person believes they will.

We still don’t know how much of the effect of seasickness remedies is due to their pharmacological action and how much is due to belief. As the abstract says, further research is needed—specifically, more randomised double-blind controlled trials comparing treatments with placebos, where neither the participant nor the administrator knows which tablet or treatment was given until after the study.

Studies of this kind have already been conducted on all the established medications. In addition, a new class of drugs—Neurokinin-1 (NK-1) receptor antagonists—is under development. However, they have not yet produced convincing evidence to satisfy the FDA regarding effectiveness. Nonetheless, this represents the first novel approach to motion sickness treatment in many years.