Sleep apnea may affect memory of everyday events

Sleep apnea may affect your ability to form spatial memories utilised for everyday tasks, such as remembering where you parked your car, a new study has found.
The study demonstrated through the playing of a specific video game that disruption of rapid eye movement (REM) sleep as a consequence of sleep apnea impairs spatial memory in humans even when other sleep stages are intact.
Spatial memory is utilised for everyday tasks, such as remembering the location of a favourite restaurant or remembering how to get home even if you are required to take a detour from your typical route.
This type of memory is particularly affected in Alzheimer's disease.

The research, led by Andrew Varga, clinical instructor of Medicine in the Division of Pulmonary, Critical Care and Sleep Medicine at NYU Langone Medical Center, builds on earlier studies in rodents demonstrating that deprivation of REM sleep has detrimental effects on memory.
This is the first study to demonstrate the importance of REM sleep for spatial memory in humans, and to document the negative consequence of sleep apnea on spatial memory.

"We've shown for the first time that sleep apnea, an increasingly common medical condition, might negatively impact formation of certain memories, even when the apnea is limited to REM sleep," said Varga.

Varga and colleagues recruited 18 subjects with severe sleep apnea who also are treated with nightly use of a continuous positive airway pressure (CPAP) machine.
Individuals spent two different nights in the NYU Sleep Disorders Center's sleep lab, during which time they played video games before and after sleep.
Subjects were first given a baseline examination using the video games before any observation of their sleep patterns. They used a joystick to navigate through one of two unique, computer-generated 3D spatial mazes.
Then, during one night's sleep, subjects used their therapeutic CPAP as they normally would at home. On the other night, their use of CPAP was reduced during REM sleep, thus allowing sleep apnea to occur.

When sleep was aided by therapeutic CPAP all night, researchers observed a 30 per cent overnight improvement in maze completion time from their baseline examinations.
When REM sleep was disrupted by sleep apnea, there was not only no improvement from baseline testing, but, in fact, subjects took 4 per cent longer to complete the maze tests.
When sleep apnea occurred in REM sleep, subjects did not experience delayed reaction times on a separate test to measure attention, called a psychomotor vigilance test.
Varga said that this suggests that sleepiness or lack of attention were not reasons for the decline in spatial memory, as indicated by the maze performance after experiencing sleep apnea in REM sleep.

The study is published in the Journal of Neuroscience.