Everest study shows neuron loss when climbing

Researchers have discovered that climbers could suffer a reduction in brain size during high climbs.

Loss of brain matter in motor activity regions isn’t ideal when climbing

A study of professional mountain climbers has shown that high-altitude exposure can cause subtle white and grey matter changes to the area of the brain involved in motor activity.

“Our results provide evidence that extremely high-altitude climbs with no external oxygen supply may cause subtle changes in brain tissue, even when well acclimatised individuals do not experience any neurological symptoms,” said study leader Dr Margherita Di Paola from the Neuroimaging Laboratory at the IRCCS Fondazione Santa Lucia in Rome.

The researchers took MRI scans of nine world-class mountain climbers, who had been climbing for at least 10 years, before and after expeditions to Mount Everest (8,848 metres) and K2 (8,611 metres) without an oxygen supply. They compared their MRI brain scans with 19 age and sex matched healthy control subjects.

The results - published in the European Journal of Neurology - demonstrated that the climbers showed a reduction in both the density and volume of white matter in the left pyramidal tract, near the primary and supplementary motor cortex, when their baseline measurements were compared with the control group.

The researchers took the first scans eight weeks before the expedition began and the second set eight weeks after they returned. One climber reached the top of Everest and K2 and two reached the top of one mountain. The remainder reached altitudes of over 7,500 metres and spent at least 15 days over altitudes of 6,500 metres. A number of neuropsychological tests were also carried out to assess the climber’s cognitive abilities, such as memory and motor functions.

“Despite the loss of grey and white matter, the climbers in our study did not suffer any significant neuropsychological changes after the expedition” said Dr Di Paola. “Some of the subjects did show abnormal scores on the neuropsychological tests, but in these cases there was no significant difference between the baseline and follow up results. This suggests that there were no significant changes as a result of a single expedition.”

Overall, the researchers found that the cognitive abilities that were most likely to be affected were the climbers’ executive function and memory. But rather, says Di Paola: “The changes in white and grey matter appear to be highly specific to regions of the brain involved in motor activity.”