Sleep and Alzheimer's

Sleep and Alzheimer's

By Ryan Lester, PA-C

Alzheimer’s is the only disease in the top 10 leading causes of deaths in the United States that cannot be cured.

There has been an 89% increase in deaths due to Alzheimer’s between 2000 and 2014.

What causes Alzheimer’s? We don’t know for sure, but we do know that in autopsy studies, the people with clinically diagnosed AD based on symptoms (memory loss, personality changes, confusion, decline in executive function) had significantly more deposits of two specific proteins in a very predictable area of their brain called the hippocampus. These proteins are called beta-amyloid and tau.

What does this have to do with sleep?

A study in mice at the University of Rochester in 2012 demonstrated that our brains have a sewage system (glymphatic system) that washes away metabolic debris during a specific period of sleep called non-REM or deep sleep. One of the proteins found in that metabolic debris was beta-amyloid, that’s right…the previously mentioned bad actor that we know is strongly associated with your risk of developing Alzheimer’s.

Associative studies in humans using PET scans have shown a marked buildup of beta-amyloid in specific regions of the brain in those who slept 7 hours or less compared to 7 hours or more over their lifetime. Although these are only associative evidence, this was causally demonstrated in animals whose deep sleep was removed or fragmented.

Still not convinced?

This randomized, placebo controlled, double-blinded, clinical trial in 2017 may change your mind. In this study, they took 22, cognitively normal people between the ages of 35–65 and randomized them to two sets of sleep protocols, ≥28 days apart. In the sleep disruption protocol, they introduced auditory tones that selectively interfered with and prevented the participants deep sleep. In the control protocol, they had the participants wear earphones, but no tones were delivered, resulting in their baseline sleep structure. Participants had a sample of cerebrospinal fluid taken from their lower back (lumbar puncture) after each sleep protocol, to measure various proteins circulating in their brain, including beta-amyloid. The results?

“The SWA (deep sleep) disruption protocol decreased SWA as measured by delta power by 23 (95% confidence interval 14–32) μV2×s. SWA disruption was strongly and significantly correlated with amyloid-β40, such that more SWA disruption was associated with greater increases in amyloid-β40 (Fig. 1A). This effect was specific for SWA disruption, and not for total sleep time, non-REM time, REM time, or sleep efficiency (Fig. 1B–E).“

It demonstrated that by removing deep sleep from the participants sleep cycle, it significantly increased circulating levels of beta amyloid in their CSF.

Genetics and Alzheimer’s

So how does all this information really apply to you? After all, most of us may know an uncle or family friend who is known for only sleeping 5–6 hours per night for most of their lifetime and lived well into their 80’s or 90’s with minimal cognitive decline. Alternatively, you may know people who were committed to sleeping at least 8 hours each night and still developed some type of dementia.

Although we have identified specific genes that increase one’s risk of developing Alzheimer’s, like APOE4 (Apolipoprotein 4), there are likely other genes that play a significant role in one’s propensity to develop AD that we don’t fully understand. Given the magnitude of evidence that is strongly correlated with the importance of both the quality and quantity of consistent sleep each night, the question is simple…why take the risk?

So the next time you think you are one of the lucky ones who continues to perform at a high cognitive level despite getting less than 8 hours of sleep each night, consider the fact that we now have strong causal evidence that you may be significantly increasing your risk of developing the number one cause of age related dementia worldwide.

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