WEDNESDAY, Dec. 4, 2019 (HealthDay News) -- Antarctica is one of the loneliest places on Earth.
Endless expanses of white give way to almost complete darkness during the long winter months. Companionship is largely limited to those who've joined you in these achingly cold wilds.
That overwhelming isolation is so great that it appears to cause physical and functional deterioration in the human brain, a new study shows.
Explorers who spent 14 months in Antarctica at Germany's Neumayer III station experienced shrinkage in critical regions of their brains, the study found. These changes in brain structure was associated with poor performance on brain tests related to attention and spatial awareness, researchers report.
"We saw volume decreases in the hippocampus, and what was surprising is that the decreases were so pronounced," said lead researcher Alexander Stahn, an assistant professor of psychiatry with the University of Pennsylvania's Perelman School of Medicine. "It was an average of about 7%, which is really big in terms of brain changes."
These results indicate a potential hazard for space exploration that will have to be overcome before mankind travels to Mars and farther out into the solar system, said Dr. Alejandro Rabinstein, a neurologist with the Mayo Clinic in Rochester, Minn.
"This suggests that there is a vulnerability of certain parts of our brain to being isolated," said Rabinstein, who wasn't involved with the study. "Social or environmental isolation could be a stressor to the brain that affects the brain in its most vulnerable areas.
"That the brain can change over 14 months by not using it, it's quite a scary thought," Rabinstein concluded.
Stahn and his colleagues are interested in the effect of isolation on humans, and deemed Antarctica one of the best places on the planet to observe the effect of a naturally hostile environment on healthy, relatively young adults, he said.
Nine polar explorers -- five men and four women -- agreed to participate in the study. All were set to spend over a year in relative isolation at the German Neumayer III research station in Antarctica.
Prior to their mission, the explorers underwent MRI scans of their brain. The scans particularly focused on the hippocampus, a region of the brain associated with space and memory.
The hippocampus has been shown to be vulnerable to stress, but it's also "one of the very few regions in the brain that's capable of creating new neurons," Stahn explained.
The explorers regularly engaged in computer-based brain function tests during their Antarctica mission. They also provided blood samples to track their levels of brain-derived neurotrophic factor (BDNF), a protein responsible for promoting the growth of nerve cells and synapses in the brain.
Upon returning home, the researchers underwent final MRI scans, blood tests and brain function evaluations, to see how they compared to the beginning of the trek.
The results were concerning.
Along with the shrinkage of the hippocampus, the explorers experienced reductions in the volume of their prefrontal cortex and other brain regions, Stahn said.
In addition, there was an average 45% decrease in the explorers' blood levels of BDNF during their mission, "which is substantial," Stahn said.
The explorers with the most brain shrinkage also performed more poorly in tests judging spatial awareness and selective attention.
The loss of selective attention might mean that a person who intends to drive to the grocery store instead turns their car toward their route to work, Stahn said. They also would find it more difficult to ignore irrelevant information when working on a task.
Poor performance on spatial awareness might mean that a person would have trouble judging distance, location or position of different objects -- for example, the ability to point out a specific window in an office building.
"It's interesting that the spatial processing would be reduced," Rabinstein said. "I can only assume that in Antarctica all of the space around you looks the same, reducing the stimulation of the areas of the brain that respond to spatial information."
There's some evidence these effects persist. A month and a half after returning to Europe, the explorers' levels of BDNF remained lower than usual, Stahn said.
Researchers are still tracking the progress of the explorers to see how quickly they will recover from their time in Antarctica. While the brain deterioration is concerning, Stahn believes that the explorers will bounce back eventually.
"I'm pretty sure that the brain is highly plastic in both directions," Stahn said. "There are negative effects, but it can also respond quickly to positive effects."
Stahn thinks time spent outside, with exposure to lots of different sensory stimuli, will feed the explorers' brains and help them recuperate. Diet, exercise and sleep also will help.
The researchers are also investigating ways to predict who might be most vulnerable to these brain changes, and possible preventive measures that could be employed while in isolation.
One possible preventive measure involves riding a stationary bicycle and pedaling through a virtual environment, which would provide both exercise and sensory input, Stahn said.
The findings were published Dec. 5 in the New England Journal of Medicine.
The Albert Einstein College of Medicine has more about the health effects of isolation.