High-altitude climbing can damage the brain. (Tony Smith/The New York Times)If you’ve ever fantasized about scaling Mount Everest, think again. A new study of professional mountain climbers shows that high-altitude climbing causes a subtle loss of brain cells and motor function.
Italian researchers used magnetic resonance imaging to look at the brains of nine world-class mountain climbers who had at least 10 years of experience, including expeditions to Mount Everest and K2. The climbers ranged in age from 31 to 52, with an average age of just under 38, and were used to climbing to altitudes of at least 4,000 meters (two-and-a-half miles, or over 13,000 feet) several times a year.
The scientists, who published their findings in the October issue of the European Journal of Neurology, compared the climbers’ M.R.I. brain scans with 19 age- and sex-matched healthy control subjects. A number of neuropsychological tests were also carried out to assess the climbers’ cognitive abilities, including memory and motor functions.
On scans, the climbers showed a reduction in both white and gray matter in various parts of the brain. Overall, the researchers found that the cognitive abilities that were most likely to be affected were the climbers’ executive function and memory.
Six of the nine climbers had lower than average scores on the Digit Symbol test, which measures executive functions. Three out of nine scored lower than average on memory tests, while four scored below average on a visual-motor function test. The study authors noted that the results “are most likely to be due to progressive, subtle brain insults caused by repeated high-altitude exposure.”
Other studies have shown links between brain problems and repeated exposure to extreme conditions. The British Journal of Sports Medicine reported in 2004 that scuba diving may have long-term negative effects on the brain, particularly when performed in extreme conditions, such as cold water, more than 100 dives per year, and diving below 40 meters.
And last year, researchers at New York University noted that high-altitude illness is a growing concern in sports medicine given the increasing popularity of extreme sports like high-altitude mountaineering, skiing and snowboarding. The report noted that about 20 percent of tourists to Colorado report acute mountain sickness, and complications arising from sports activities at high altitudes, such as the potentially fatal conditions of pulmonary and cerebral edema, are on the rise.
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From 1 to 25 of 93 Comments
Another one to watch out for is pulmonary congestion and orthopnea caused by altitude-related capillary leak. It is fairly common.
What is this? Your lungs fill up with fluid and you have to sleep sitting up. It has nothing to do with congestive heat failure. If you’ve had this before, you should inform your doctor, and he/she will give you a prophylactic diuretic.
— jackEeek!
— MichaelDo the studies discuss causation or just merely a correlation? What if high altitude climbing just happened to attract people with sub-average executive functions, etc., rather than sub-average executive functions being diminished by high altitude climbing?
— Jennifer B.I would be astonished if very many Americans fit the criteria to be at risk for this kind of brain-cell loss. The study focuses on mountain climbers with more than 10 years’ experience, and who regularly go to 4,000 meters (that’s a bit over 13,123 feet) several times in one year.
Even here in Colorado, where “bagging fourteeners” is a common pastime, most Coloradans are at a higher risk of heart disease, strokes and diabetes — diseases that strike sedentary people in large numbers — than they are for elevation-related brain-cell loss.
— Ashley Trailrunner, ColoradoIt’s statistically unlike that any individual’s score would exactly equal the average, so does this result imply, for example, that “six of the nine” scored HIGHER than average on the memory scale? I’m genuinely confused about what inferences one can reasonably draw from this study.
— Bill Fortney“Six of the nine climbers had lower than average scores on the Digit Symbol test, which measures executive functions. Three out of nine scored lower than average on memory tests, while four scored below average on a visual-motor function test.”
Wouldn’t you expect at least 3-4 out of 9 to be below average? If there aren’t outliers, 1-3 would be average, 3-4 each above and below average, as an estimate.
It also doesn’t test whether they had a decline or if they always had a tendency that way at the start, perhaps associated with the personality of a climber, as Jennifer says in #3.
Only the 6/9 who scored low on the executive test would be worrisome, provided that it was actually a decline and not a preexisting tendency.
Perhaps the original paper makes more sense statistically but, at least in this summary, the numbers really doesn’t strike me as significant.
— PatriciaJust curious if full time high altitude living — above 7000′ causes any long term cognitive or physiological problems.
— TamarI was just reading that even heart-healthy amounts of red wine can shrink the brain. So what is a person to do? At my age I need my heart more than my mind. So maybe I’ll give up plans to scale Everest, and just have another glass of wine.
— BruceThere’s lies, damned lies, and statistics.
— Bendid they see a dose-related response not related to age? though that’s probably too hard to do with such a small N…
— RosemaryI’ve climbed above 20,000′ several times and have been over 13,000′ repeatedly since ‘57 including several times annually in most years since the early ’80s.
Shoot! Now I can’t remember the point I was going to make….
Oh, I know. When I was doing expeditions to 6 and 7 thousand meter peaks we all knew the Everest climbers had been identified as losing a few IQ points on their climbs. When people asked why we climbed anyway, we answered that we were too brain damaged to know better. When they asked why we started down (up?) such a crazy path, we just said we couldn’t remember.
FROM TPP — well now at least we know climbers don’t lose their sense of humor.
— Tommy T. Goodrich,TX/USAI would think that most climbers would have sub-average executive function. Not that this is necessarily an impairment, but mountain climbing into “the death zone” is not a logical pursuit…it is more poetic and abstract. Anyone who is an expert at keeping their desk clean would probably fret messy things like frostbite, avalanches, and pulmonary edema.
— Chip VentersAGREE WITH JENNIFER B. (SHE IS CLEARLY NOT A CLIMBER.)
— HANNAHTHIS NEEDS TO BE STUDIED PROSPECTIVELY TO DRAW ANY REAL CONCLUSIONS……(OR NOT)
The silver lining of this cloud, of course, is that by reading this article perhaps fewer people will be encouraged to visit, and thereby degrade, some of the most beautiful, remote and fragile ecosystems on our planet.
— RobertWe never seem to stray very far from Neil Armstrong’s reason for never exercising: with only a finite number of beats available to the heart, why “burn through them” more quickly with high cardio-load activities?
My days as a high-altitude expedition climber are among my most memorable. While I finally sailed past the sirens and came “back to earth” as a mere endurance athlete, the rest of my life has been informed by those glorious days (good and bad) in the halls of the mountain kings.
If I’m too slow to beat my son on the Wii…..what of it? I’d give up another 10% of my precious executive functions for another 10 years in the mountains.
— Jacques BoutetSeveral posters above are unclear as to where the authors set the norms for a low score on the neuropsychologic tests. It was NOT at the mean score of the control group “For each test, the cutting score, defined as the lower limit of the 90% tolerance interval around the normative mean is reported.”-so several of these climbers scored well below average.
As to causality-the only changes where causality can be inferred are the changes in the scans pre and post ascent above 7500m on K2 and/or Everest w/o supplemental O2
jennifer’s point re executive functions is valid-we can’t know, although looking at climbers who do not go as high might suggest whether or not differences are due to self selection or exposure.
IMO the significance of climbs above 4000M is nil-its their history of climbs to much higher altitudes w/o O2, I’d guess (based on O2 saturation at altitude). The history fo tehse climbers at altitudes higher than the alps wasn’t discussed in the article.
— Don TaylorI have read that Rheinhold Messner, who ascended the 14 highest peaks without supplemental oxygen, has suffered some neurological damage. Ed Viesturs has climbed all 14 the same way and summited Everest at least four times without supplemental oxygen, yet seems fully cognizant and super-healthy. I would think that how fast your brain produces new cell to compensate for any high-altitude damage would be an area they would want to study as well.
— Tom LanninVery, very interesting.
However, the study fails in omittiing several other dangers that high altitude mountaineers face: death by falling, death by hypothermia, death from avalanche, death from rock-slide, concussions from falls, frostbite, etc.
Given the risks mountaineers currently embrace, CRS syndrome in old age is, perhaps, of small consequence.
— RealistThis study (as summarized by NYT) creates more questions than it answers. It is not surprising that people who spend their lives going up to 24,000+ ft (the death zone) would have some health problems. Those people are a very rare breed. Say what you want about what motivates them, but they are the very definition of the exception to the rule. Their results don’t apply to anyone else but themselves. A better study would have compared populations of “citizen mountaineers” like those that Ashley Trailrunner describes, who regularly go past 13,000 feet, but do so in a relatively safe manner, to a control group of non-mountaineer lowland athletes.
— willFirst of all, I wonder at the small number of climbers in the investigation. Secondly, I too wonder about those who live at high altitudes in the Himalayas. Is there a way to do this test for them? I would especially like to see the test done on all those gallant, brave unsung heroes of the Himalayas, the Sherpa men AND women who regularly spend even many MORE hours and days and weeks at altitude to make it possible for the person in the tests to make their climbs, not only on Everest, but on all the major Himalayan peaks.
While I do not doubt the results of the few in the test, it would tell us SO MUCH MORE if the test were done with a proper group of men and women. Speaking personally as someone who spent a LOT of time at altitude for one long period of time, I have not found the effect described…..but then I was not tested….it is simply anecdotal evidence from personal experience.
The question really also needs to be asked: What is the purpose of such a study? To know that extreme exposure to altitude is harmful? Well, I want to know first if the participants in the study were on oxygen, or not, how long their exposure to altitude was–not just how many times per year, and what the time/altitude levels were in average over all participants. There are too many factors that make a difference to the long term results.
— Mary Margaret Revell GoodwinI agree with Jennifer B…it’s likely that there is something inate in these climbers (perhaps a result of “less white matter” or whatever) that makes them seek out the rush of mountaineering. I would also like to point out that numbers like “3 and 4 out of 9 are below average” fit pretty well with the DEFINITION of “average”
— EricaBill & Patricia- The original paper does make a little more sense statistically. It didn’t say that 6 of 9 were “below average”, for example; it actually said that their score was below *normal*. For each test, they reported the mean score and the standard deviation, and then determined a cut-off score, which they defined as “the lower limit of the 90% tolerance interval around the normative mean”.
Basically, 6 out of the 9 climbers scored *significantly* below average on the test.
Interestingly, they performed these tests before and after an expedition and found no significant change. They also saw no correlation between the neuropsychological test results and the MRI results.
They do present one piece of data that may be convincing evidence of a causal relationship between climbing and brain damage:
They took MRIs of each climber before and after an expedition, and they found a region of reduced gray matter volume/density in the left angular gyrus after the expedition.
— KTStories like this are always in demand by editors as they know Americans LOVE a good “exercise is actually bad for you” study. You should publish one of those “it doesn’t matter what you eat” studies tomorrow, as well as a “staying thin might kill you” bromide tale as well.
About 1 in a 100,000 people has to worry about this, the rest could do with far MORE climbing!
— John HagmanCould it be that we climbers enjoy a good stiff drink and a doobie at the end of every climb that is causing the loss of brain cells.
I think that after years of climbing I am in better shape than my friends who drive behind cars and buses every day on the commute to work.
— G MaleAhem. The study examined the effect of “extremely high altitude” climbs of 28,000+ feet on “world-class” climbers who were accustomed to several 13,000-14,000 climbs a year, that is, those who were acclimated to moderately high-altitude climbs.
You seem to conclude from this information that if both the flatlander at 10,000 feet and the experienced climber at 28,000 feet experience altitude sickness, it must follow that a flatlander must necessarily suffer the same cognitive damage as the high-altitude climber. None of the articles you cite support that conclusion.
Perhaps, though, this study finally explains the extreme boneheadedness of extreme mountaineers who spend their lower-elevation winters ice climbing, certainly one of the most masochistic forms of the sport.
— Lenore