MAKING MOTION SICKNESS STOP: Some dizzying experiments are underway to help find better treatments for motion sickness.
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James Locke, a flight surgeon at NASA's Johnson Space Center in Houston, has made dozens of people sick in the name of science. When he puts subjects in a spinning chair designed to induce motion sickness, roughly 70 percent of them succumb—and at nearly the exact same point on each ride. Locke has used this research and his work with shuttle astronauts to determine which medications and doses best prevent the nausea and vomiting associated with motion sickness.
Unfortunately, while the chair always goes through precisely the same motions, the real world is less predictable. In a ship at sea or on a small plane in turbulence, for example, the type and amount of motion can vary dramatically—and so can its effects on people.
Researchers like Locke, and those who work with pilots and the military's most frequent flyers, are especially keen to find better ways to treat motion sickness. And the many civilians who face nausea in cars, planes, boats or even the tamest amusement park rides would welcome a cure without the common side effects of current medications, such as sleepiness, or the questionable efficacy of alternative treatments, such as pressure bracelets. The path to those ends remains bumpy and filled with more than a few green faces, but new research is closer to finding the best treatments to keep both side effects and lunch down.
Eyes vs. ears
Despite decades of research, scientists are still not sure exactly why motion sickness occurs—or how. The currently accepted theory is that sensory conflict is to blame.
"Information from both our visual and vestibular systems is processed by the brain to match it all up. Your vestibular system—your inner ear—is tuned to a terrestrial, 1G environment," Locke says. "When you move [yourself] around, changes in your vestibular system match up with what you're seeing. But [riding] in an airplane or car, your inner ear signals that you're moving, but your eye says you're sitting still" because your body is not moving in relation to its immediate environment—such as the seat you're sitting in, the back of the seat in front of you and the floor beneath your feet.
Why this conflicting input actually causes symptoms such as vomiting is also fairly unclear, says Edwin Park, a neurologist at the Naval Aerospace Medical Institute in Pensacola, Fla.. "Most research has only revealed bits and pieces, and it's all speculation on how it goes together."
A number of neural pathways apparently can activate the brain's vomiting center, thought to be located in the medulla. Studies have shown that certain medications—antihistamines, anticholinergics, amphetamines and serotonin agents—are effective in treating motion sickness, which suggests that it involves the related neurotransmitters: histamine, acetylcholine, noradrenalin and serotonin. Locke says some agents used to treat nausea from other causes, such as food poisoning and chemotherapy, curiously fail to work on motion sickness. Thus, these reactions likely do not involve the same brain pathways as motion-induced nausea.
Locke's data suggest that roughly 30 percent of the population is naturally immune to motion sickness, at least in most conditions. Studies as to why some people are susceptible and others are not have been inconclusive, he says: "So far, we're unable to predict who gets it and who doesn't." Most research has focused, instead, on what helps those who do succumb in controlled conditions, which may also help scientists better manage the condition in the real world.
Drugs and other treatments
Unimpressed with the effectiveness of over-the-counter meds, NASA researchers have experimented with combinations of more heavy-hitting drugs to strengthen astronauts' stomachs, so to speak. Through trial and error, Locke has found that a combination of oral scopolamine, to suppress vomiting, and dextroamphetamine, to counteract scopolamine's potential to induce drowsiness, reduced the incidence of motion sickness from 70 percent to about 12 percent among passengers in the "Vomit Comet"—a DC-9 aircraft used to achieve brief periods of zero gravity as part of NASA's Reduced Gravity Program. Oral or injected scopolamine takes effect more quickly and can be administered in higher doses than the patches commonly used by the general public, but the drug is not as readily available to the public in those forms (NASA orders its own supply).
Multiple studies have shown that people with a history of suffering from migraines are more susceptible to motion sickness. Joseph Furman, a professor in the department of otolaryngology at University of Pittsburgh, recently published a study showing that patients who were prone to migraines that are accompanied by dizziness responded to rizatriptan, a serotonin agonist that is often prescribed to help stop migraine headaches in their early stages. But like motion sickness, scientists do not really know why people get migraines, Furman says. And determining whether the drug would have the same vertigo-alleviating effect on people who do not would require a larger study of rizatriptan's application specifically to motion sickness.
Additional factors might complicate the full biophysiology of motion sickness, some experts argue. "To say a certain percentage of the population is susceptible to motion sickness is probably an oversimplification," Park says. "There are so many variables involved, including the type and frequency of motion, and a range of tolerance and frequency." In fact, testing motion sickness in the real world is so difficult precisely because conditions and individuals vary so much on a case-by-case and incident-by-incident basis.
Park thinks anxiety makes people more susceptible, for instance, and having a sense of control over a situation makes them less so—which might explain why people are more likely to get sick riding in a car or aircraft than when they are driving or at the controls. He has used desensitization training, exposure to motion in an artificial environment (the same type of spinning chair Locke uses), and biofeedback, in which subjects learn to control their own breathing, heart rate and other physical responses, to help flyers deal with motion sickness.
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14 Comments
Add CommentJames Locke is quoted:
Reply | Report Abuse | Link to this"...But [riding] in an airplane or car, your inner ear signals that you're moving, but your eye says you're sitting still."
I wonder if simply looking out a window to focus on the external environment (which contains clues of your motion) might relieve symptoms?
My wife (who also gets migranes) has had some success with the sharper image battery powered watch. It sends a small electrical charge into your wrist and can be set to different intensities. She has found it useful on flights (and cruises, although wearing it can get uncomfortable after several hours.), and she says it helped with nausea during pregnancy some as well.
Reply | Report Abuse | Link to thisWhen sharper image closed, this watch (with the replacable battery) became available only in Europe, but can be bought in the US still as a disposible watch (a scam by the new owner of the technology to get you buy it over and over again)... they advertise it now for people undergoing cancer treatments to help with the nausea, so I guess they figure insurance will just pay for it over and over... when the original design was fine (you could just pop in new batteries)... gotta love the "free" market!
At any rate, we've had several other people borrow it and it worked for them as well... it certainly beats getting drugged up.
"But like motion sickness, scientists do not really know why people get migraines . . . ."
Reply | Report Abuse | Link to thisSo motion sickness doesn't know why people get migraines? And scientists are like motion sickness? Alas for the days when the prose in SA was as good as the science coverage.
Epinewton, used for epilepsy, works particularly well against motion sickness. Use 3.5mg Epinewton per 1 kg of bodyweight two hours before being subjected to the cause of the motion sickness. There are no side effects like with most other drugs used against motion sickness.
Reply | Report Abuse | Link to thisThere was a theory a few years ago that motion sickness was an evolutionary adaption to the danger of eating poisonous alkaloid berries. Disorientation of movement and vision was a symptom of such poisoning. Vomiting as a reaction to that dislocation of the senses was therefore a successful survival strategy.
Reply | Report Abuse | Link to thisFor myself open boats at sea and soft-sprung coaches will do it. Also any motion where I can't easily focus: swings; roundabouts; car side-window views of hedges. Even walking quickly through a sequence of strong shadows of trees or vertical railings gives instant nausea. "Avomine" used to be the sure-fire preventative - although on one occasion it left me like a zombie after an afternoon being driven along hedge-lined, zig-zagging country roads at high speed.
My migraines seem to have moderated with age. Eating something fatty at the zig-zag rainbow vision distortion stage seems to prevent the usual blinding headache and nausea.
One hardly needs research to draw these conclusions.Since vertigo results from the two systems being out of synch, the solution can only be one of the following: 1)the systems need to be in synch, put in synch, or prevented from getting out of synch or 2) one or other or both systems need to be suppressed to prevent or alleviate symptoms, but without causing unwanted side effects.Since the variables are nearly infinite, the search for a "cure" for vertigo is a fool's errand.
Reply | Report Abuse | Link to thisI get world class motion sickness, takes most of the fun out of sailing or kayaking. (I also have migraines)
Reply | Report Abuse | Link to thisThere is no question that if I can keep my attention focused on the horizon line, I don't get sick. Just looking down to take a fish off a hook, however, is enough to do the trick. The speculation that keeping the attention on the fixed horizon reduces the conflict between the inner and outer signals seems right on to me.
Traversing the Atlantic by sea three times in the early 1950s, I found that I was nauseous on the first day of each voyage, but then a small upchuck got me my "sea legs," the same phenomenon occurring on the old flying boats on which we used to fly to Bermuda. No need for airsickness bags on jets, so those make nice lunch bags if you get off the plane with unused ones.
Reply | Report Abuse | Link to thisI am somewhat surprised that there is no mention of Dramamine for this condition as that is hugely effective and over the counter. One need not drop Scopalamine which is surely more risky than Dramamine which works excellently in my experience. I can take it and manage to eat with gusto on a rough plane flight when otherwise..well..we need not go into details! It affects one's vision somewhat and can be a soporific but it is surely better than having one's head in a sickbag.
Reply | Report Abuse | Link to thisThe article hints that there is no quick fix using most known medications. It is mostly in the head.
Reply | Report Abuse | Link to thisOnce when at an amusement park, inside a vertical axis cylinder I was able to exit before the compulsory waiting period after the ride stopped.
I had forced my head around 180 degrees, facing outwards, while strapped in for the last few revolutions of the ride and it briefly amplified the spinning effect. I then turned my head back to face the center and was able to walk out without any ill effects of dizziness.
Elsewhere it maybe genetic, but I believe it is still a learned adaptive behaviour. Native people who work at high elevations accept warning signals from normal swaying.
Erratic driving was probably what often made my oldest daughter carsick except when she said she was riding with me. I had taken extensive care to perform all motions predictably and in anticip[ation of wind gusts, curves, starts and stops, once even through a forbidding snowstorm. She now no longer complains of carsickness with anyone.
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Reply | Report Abuse | Link to thisMotion sickness is caused by exposure to infrasound.
Reply | Report Abuse | Link to thisMotion sickness is caused by exposure to infrasound.
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