Having trouble forming new spatial memories of everyday events, such as recalling where you parked the car? It could be a sign you're suffering from sleep apnea, a study suggests.
Sleep apnea, caused by the airway collapsing during sleep and interfering with normal breathing, affects 4 percent of Americans overall and as many as 25 percent of middle-aged men, the researchers note.
Scientists at New York University's Langone Medical Center say they've conducted experiments using video games that suggest disturbance of rapid eye movement (REM) sleep caused by sleep apnea can impair spatial memory even when other stages of sleep are left intact.
Their study is the first to demonstrate in humans the importance of REM sleep for spatial memory and the negative consequence of sleep apnea on such memory, the researchers report in The Journal of Neuroscience.
Our spatial memories are involved in everyday tasks such as recalling the location of a favorite restaurant, or remembering the way home or recalling where you last left your car keys in the house.
Alzheimer's disease in particular affects this kind of memory, and is likely a root cause why caretakers of individuals suffering from it often find them wandering lost, the researcher say.
Although less serious for those with sleep apnea, it should still be taken into account by physicians, they say.
"Our findings suggest memory loss might be an additional symptom for clinicians to screen for in their patients with sleep apnea," says study leader Andrew Varga.
In the NYU study, 18 subjects with severe sleep apnea played video games requiring them to navigate through a special maze, doing so both before and after sleep to determine a performance baseline.
The subjects were all on a treatment regimen of regular nighttime use of a continuous positive airway pressure (CPAP) machine to ward off apnea.
In the study, for one night's sleep they used the CPAP machine as the normally would at home, and on another night the CPAP use was reduced during periods of REM sleep, allowing an occurrence of sleep apnea.
Comparing the performance on the video game following both nights, the researchers found a 30 percent improvement in completing the 3D maze after the nights of normal CPAP use compared to their baseline, but a 4 percent decrease in their performance after the nights of induced sleep apnea.
"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," Varga says.
