Sleep and Memory Loss

What can you do to prevent memory loss?  Sleeping well may be a potent strategy.

An article recently published in JAMA explored whether sleep apnea, or repeated pauses in breathing during sleep, increased risk of subsequent dementia.  298 elderly women underwent sleep studies.  105 had sleep apnea.  Those with sleep apnea had almost twice the risk of subsequent development of cognitive impairment.  This study does not prove that sleep apnea causes dementia, or that treatment of sleep apnea reduces dementia risk, but it provides an important clue that the two disorders interact.

Not only might sleep apnea contribute to dementia, but healthy sleep may help the brain fight dementia.  Here is the background:  Several factors likely contribute to development of Alzheimer’s disease.  One of these factors is buildup of plaques between brain cells.  The main ingredient of these plaques is amyloid beta.  In the fluid surrounding neurons (known as cerebrospinal fluid or CSF), the more amyloid beta there is,  the more that precipitates out, forms plaques, and contributes to Alzheimer’s disease.

A 2009 mouse study, published in the premiere journal Science, showed that CSF amyloid beta decreased in sleep and increased during wake.  Sleep deprivation spiked amyloid beta levels.   A paper in the Archives of Neurology aimed to replicate these mouse findings in humans.  Volunteers agreed to have levels of spinal fluid amyloid beta checked hourly.

In young volunteers, amyloid beta rose during wakefulness and fell during sleep.  In older volunteers without evidence of amyloid brain plaques, amyloid oscillated with wake and sleep, but less robustly than in the young.  In older volunteers with evidence of amyloid plaques, amyloid levels didn’t budge during sleep.

The researchers hypothesize that wakefulness leads to amyloid, and the brain clears amyloid during sleep.  In the young, this process is robust.  In the elderly, persistence of amyloid clearing may protect the brain from plaque accumulation.  Failure of this process may foster amyloid buildup in the brain and dementia.

So what does this mean for those who want to prevent dementia and those who have dementia?  If you have trouble sleeping, feel sleepy during the day, snore, or carry excess weight, you might have sleep apnea.  If you can sleep well but don’t give yourself the opportunity to sleep for 8 hours each night, do your best to prioritize sleep.  Let your brain cleanse itself.