Sleep apnea tied to memory problems

The ability to remember locations and directions may suffer when deep sleep is disrupted by breathing difficulties, a new study suggests.

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.

“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.