High summits 'could harm brain'

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Top mountaineers may be suffering subtle brain damage each time they reach the upper slopes of the world's highest peaks, say scientists.

Italian researchers scanned "world-class" climbers before and after expeditions, publishing their results in the European Journal of Neurology.

They found changes in brain tissue even though, outwardly, the climbers had no obvious new neurological problems.

The most likely cause was a lack of oxygen at high altitudes, they said.

Most climbers are aware that if you are going over 8,000 metres, there may be a small amount of damage to the brain associated with that Dr Mike GrocottUniversity College London

At the summit of Everest, the world's highest mountain, the concentration of oxygen in the air is reckoned to be only a third of that found at sea level, more than 8,000m lower.

All of the nine male climbers involved in the study, at the IRCCS Fondazione Santa Lucia in Rome, had reached their summit without the use of a supply of extra oxygen, a frequent practice among leading mountaineers.

Before the trip, they underwent MRI scans, and were checked for any neurological illnesses, then matched against "control subjects" of the same age and sex, who had never climbed above 3,000m.

Three of the climbers reached the top of at least one 8,000m peak, while the remainder reached altitudes of at least 7,500m, spending in excess of 15 days above 6,500m.

When they were scanned eight weeks after returning, compared with the "controls", there was a fall in the density and volume of brain tissue in two parts of the brain, the "left pyramidal tract" and the "angular gyrus".

Memory worry

However, Dr Margherita Di Paola, who led the study, said that this reduction did not appear to have a direct impact on their neurological performance.

"The climbers in our study did not suffer any significant neuropsychological changes after the expedition," she said.

However, some abnormal results on both the "before" and "after" tests, she said, might be the result of small, progressive brain damage caused by repeated trips to high-altitude.

These included tests on memory and brain functions such as the ability to anticipate outcomes and adapt to changing situations.

Dr Mike Grocott, from University College London, who has himself helped carry out research high on Everest into the effects of altitude, said that there was other evidence of the potential impact of high-altitude mountaineering on the brain.

He said: "Most climbers are aware that if you are going over 8,000m, there may be a small amount of damage to the brain associated with that.

"Even a year later, people might not be as sharp as they were before."

He said that the research did not show this type of climbing to be unacceptably dangerous, but should be viewed alongside other sports such as football, where studies suggests that even too much time spent heading the ball could cause subtle brain injuries.