What's Up Doc? Motion sickness occurs when brain can't consistently interpret signals

Dr. Jeff Hersh
·4 min read

Q: Can anyone get motion sickness when the seas are especially rough?

A: There are three major ways we sense that we are moving. These include:

  • Vision. We perceive the outside world is moving with respect to us, whether 1.) we are moving ourselves, 2.) the thing(s) we are looking at are moving, or 3.) it is only an image that is moving (as may occur when we are looking through virtual reality goggles).

  • The vestibular system. This is essentially a balance and orientation system that can tell if/how our head is moving/tilted with respect to gravity. This system, which resides in the inner ear, is comprised of three semicircular canals that are filled with fluid and that have tiny hair-like sensors to determine if the fluid levels change (which occurs when the head position changes with respect to gravity) and then sends signals to the brain noting these changes. This system is also very important for us to maintain balance, both when we are stationary and when we are moving.

  • Proprioception. This is a system of sensors in our joints, muscles and tendons that sends signals to the brain when these structures move/change position. Not only is this important for us to move/walk/etc., but it also signals that we are "swaying" even when we are essentially stationary (so of course is also very important to balance).

Dr. Jeff Hersh
Dr. Jeff Hersh

Motion sickness is thought to occur when there is some discrepancy in how the brain is able to interpret the signals it gets. Consider the example of when our vestibular and proprioception systems say we are moving due to a pitching boat, but our vision says we are not moving (if we are inside and unable to visualize the boat’s movement with respect to the horizon). The result of this discrepancy of signals is that we may develop symptoms of motion sickness.

The most common symptom of motion sickness is nausea (with or without vomiting) and/or queasiness, but may also include a "dizzy" feeling, increased salivation, burping, fatigue/malaise and/or other symptoms.

Although different people have different susceptibilities to motion sickness (including sea sickness), essentially everyone can potentially get some motion sickness symptoms in certain circumstances. However, in any given situation (for example, a boat on rough seas), some people may develop symptoms of motion sickness and some may not. One study of more than 20,000 people on more than 100 different sea voyages found that about 20% had mild symptoms, 5% had moderate symptoms and 5% experienced severe symptoms. But the rest reported minimal or no symptoms.

People with a history of motion sickness are at increased risk of developing it in a given circumstance, and it is slightly more common in women and in people with a history of migraines or certain other conditions (such as Parkinson’s disease).

Noting that motion sickness is likely due to an inconsistency of signals to the brain, the first step is to prevent this from occurring. This can be done by:

  • Looking at the horizon so the visual information of motion is consistent with other signals.

  • Drinking adequate fluids (not alcohol) and getting fresh air.

  • Not reading and/or looking at a screen when on a pitching vessel.

  • Laying flat with eyes closed (so as to take "vision" out of the mix of signals), or at least tilting your head back 30 degrees or so.

  • Controlling the motion (for example, driving the vehicle when this is possible).

As these steps are not always possible and/or effective, there are treatments for motion sickness, which include:

  • Things to minimize nausea, such as minimizing alcohol and spicy foods, avoiding strong/noxious odors (pleasant odors may actually be beneficial) and potentially eating ginger lozenges/candies (ginger is a well known anti-emetic). In some cases, other anti-nausea medications may be indicated.

  • Acupressure methods, such as applying gentle pressure/massage to the palm side of the center of the forearm a couple of inches to the elbow side of the wrist. There are even commercial arm bands that do this (although the data on their efficacy is limited).

  • Medications. This includes antihistamine medications and possibly certain other medications. One of the most common medications used for this is a scopolamine patch, which is applied to the skin and allows the medication to be gradually and continuously be absorbed through the skin.

Most people acclimate to the motion ("get used to it") after two or three days, so if motion sickness affects you on your trip, hang in there and treat the symptoms as needed. Hopefully your symptoms will improve and you will still be able to enjoy your trip.

Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com

This article originally appeared on MetroWest Daily News: Dr. Jeff Hersh offers strategies to help combat motion sickness