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 People with sleep apnea tended to score worse on spatial memory
tests after sleeping without their breathing aid, compared to
mornings after they’d used their breathing aids at night,
researchers found.
“There had been some evidence in animal models that REM sleep or
dreaming sleep is important for spatial memory, but no one had shown
or proven that in people,” said Dr. Andrew Varga, the study’s lead
author from NYU Langone Medical Center in New York City.
“Spatial memory” helps people remember how to get to their
children’s schools, or where they left their keys, for example.
It’s thought that people may have difficulty forming new spatial
memories if their deep sleep and shallow sleep are interrupted,
according to Varga.
People with sleep apnea - some 18 million Americans, according to
the National Sleep Foundation - experience numerous pauses in
breathing that can last from seconds to minutes. As a result, people
with sleep apnea are often tired when they wake.
To see whether individuals with sleep apnea tended to have more
difficulty forming new spatial memories, the researchers recruited
18 such people to spend two nights in their sleep center, about two
weeks apart.
The volunteers had always slept with a so-called CPAP machine to
eliminate sleep apnea. During one night in the sleep lab, they slept
with CPAP. The other night, their CPAP was reduced or turned off
during deep sleep to induce apnea.
On each of the two nights, before they went to bed, participants
were asked to complete a video game maze. The next morning, they
completed the maze again.
After a night of sleep with their CPAP machine, the time it took the
volunteers to complete the maze improved by about 30 percent. They
also traveled farther in the maze and spent less time backtracking.
But after a night with sleep apnea, the volunteers were about 4
percent slower at completing the maze, compared to the night before.
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“People had no improvement and actually on average they got a bit
worse,” Varga said. “We interpret that to mean their consolidation
in spatial memory wasn’t as good when REM (deep) sleep was
disrupted.”
The researchers can’t say whether the worse performance is directly
from the disruptions in sleep caused by the apnea, or whether it’s
the lack of oxygen the condition causes.
Varga said they are testing the apnea or oxygen question now. They
are also looking at whether apnea during shallow sleep affects
spatial memory.
“The thought is that you need both (deep and shallow sleep),” he
said. “If you don’t have one or the other, you don’t’ have the
ability to consolidate the information.”
Varga said he hopes the results of the study, published in The
Journal of Neuroscience, will encourage more doctors to treat sleep
apnea early – instead of waiting until the condition worsens.
“Apnea is very common and has a variety of deleterious effects that
have to do not only with cardiovascular health, but also there is an
emerging dataset - of which this paper is only one piece - to
suggest there are really cognitive effects also,” he said.
SOURCE: http://bit.ly/1rG9B9I The Journal of Neuroscience, online
October 29, 2014.
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