Life may begin at 10,000 feet for many ultrarunners, but it looks like the brain may begin to slowly break down somewhere above 14,000 feet. A recent, small study in the European Journal of Neurology (abstract) showed that experienced high-altitude mountain climbers had subtle, detrimental changes to brain anatomy that controls motor skills after trips to Everest and K2. And while results of neuropsychological tests given to the climbers didn't change before and after their summits, a pretty big percentage of the climbers--all of whom had at least 10 years' climbing experience--actually "failed" the tests, meaning they didn't meet the low-end cut off for normal.
What does this all mean? It's hard to say given the very small sample size of the study, but with ultramarathoners' propensity to go high and go long, it'll give our friends and family even more evidence that we really aren't quite right in the head.
(photo by e.berg used under Creative Commons)