Last Updated on September 18, 2024 by Art

(Sleep #2 of 3) How Sleep Affects Brain Health…

Sleep apps are the easy way to gain insight into our sleep, and improve its health. The previous blog described many ways to track our sleep. This app discusses the function of sleep, and how I chose a specific app to test.

About Apps and Sleep

As mentioned in the previous blog, some apps provide sounds that help you get to sleep or stay asleep; still others are meditation aids that clear your mind. However, the app type I’m discussing today provides data about your sleep.

How can this be helpful? I think of sleep goals in two categories:

• Short term: to feel rested and energized when I wake up, and throughout the day.
• Long term: to get enough of the kinds of sleep that may help me age gracefully and stave off dementia.

I don’t have any short term sleep goals: I fall asleep easily and often sleep straight through the night. Every few hours I rouse enough to change my sleeping position (left side, right side, back) but I then go back to sleep.

I haven’t always been such a good sleeper. I used to suffer from obstructive sleep apnea, which besides being unhealthy made me an undesirable sleeping companion due to my snoring. However, I now sleep on a wedge pillow and use an oral appliance which completely eliminates apnea episodes, and also greatly reduces my snoring.

Therefore, on balance, I am happy with my sleep today. However, what about the long term?

Sleep and Dementia

Despite vigorous attempts to understand it, the brain still conceals many mysteries: how it works, why things go wrong, and how to repair them. And dementia is one of those “things.”

Alzheimer’s Disease, the most notorious form of dementia, is accompanied by physical changes in the brain: the accumulation of amyloid plaques and neurofibrillary tangles. Attempts to prevent or treat dementia often target these foreign invaders. However, no one really knows whether these features cause dementia, or result from dementia, or whether both these features and dementia arise from some other cause.

Nevertheless, there’s evidence that certain stages of sleep are important for healthy brain function. Researchers believe that both slow-wave sleep (SWS), also called deep sleep, and REM (Rapid Eye Movement) sleep, in which we dream, are important for memory consolidation, during which the brain stores new short-term memories for future use. And both are necessary to maintain healthy cognition and emotional functions.

            Research to Modify Sleep

Despite the lack of an underlying theory, there’s a lot of ongoing work. For example, some assert that slow-wave sleep can help protect against Alzheimer’s Disease. This research has encouraged attempts to increase slow-wave sleep:

• Some researchers have used hypnotic suggestion to increase slow-wave sleep; however, the resulting sleep lacks characteristics thought necessary for memory consolidation.
• Both scientists and nonscientists have treated patients with light and sound pulsing at 40 times per second. This may increase the circulation of cerebrospinal fluid through the brain, which is associated with slow-wave sleep. (FYI, on 52 nights I listened to 4 to 10 minutes of ~40Hz tones before sleeping, and saw no increase in my deep sleep time.)

Other studies disagree concerning the importance of SWS. Instead, they find evidence that Alzheimer’s Disease may be caused by:

• Too much daytime napping
• Obstructive sleep apnea events leading to less breathing and lower blood oxygen
• Poor sleep consolidation, defined as amount of time sleeping divided by the time between first falling asleep and final awakening

Art’s Theory of Sleep

What are we supposed to think about sleep when the experts never agree? It gives us permission to come up with our own theories.

Here’s mine: During waking hours our brains are bombarded with signals, both from our 5 senses and from inside us. Our brain only has so much processing capacity, and it needs to prioritize basic needs, such as food, air, water and not driving our car into a lamp post. So the brain concentrates on what’s important here and now. However, since it’s important to learn from our experience, the brain also takes notes. The brain puts them aside until nighttime.

When we go to sleep, the cacophony of sights and sounds goes mostly away. That allow the brain to turn its attention to processing its daytime notes. It calls up memories of the day’s events, decides which to keep, and where to file them. Our memories are “associative,” meaning that if we think of one item, our brains are wired to give access to other items that seem or feel similar. The brain may look for past memories that gave us feelings that were similar to a today event. Having the new memory and the past memory on stage simultaneously may inspire the story-telling part of the brain to weave them together into an adventure, which we might experience as a dream. Thus, dreams may be one way that we experience the brain’s memory storage activity.

            Sleep Stages and Brain Function

We know that SWS, deep sleep, tends to occur early in the night. This could be the brain cleaning out garbage, both logically and physically, preparing to process the day’s events. During the rest of the night, REM sleep may use dreams to sort and store memories worth keeping.

What then is dementia? It could be faulty “cleanup,” visible physically as plaque and tangles, and visible functionally by the brain’s inability to tidy up its desktop. Or it could be caused by malfunctions in any of the processing functions that occur throughout the brain. Either way, it’s plausible that if we prevent physical malfunctions like apnea, and increase our sleep consolidation, we may be also postponing or preventing dementia down the road.

Art’s Choice of Sleep Sensor

The previous blog described a wide range of sleep sensor devices and apps.

I’m familiar with polysomnography (PSG) because I participated in several lab tests for sleep apnea, both in California and Michigan. Its tangle of sensors and lab environment rule out PSG for daily consumption. The next-most-complete solution, home polysomnography, is intrusive and far from complete (it omits brain wave monitoring, and interpretation by a trained technician).

I have second-hand familiarity with sleep devices that family members are using:

• Apple Watch is a multifunction device that also has health functions, including sleep monitoring. It’s not suitable for me because I have stopped wearing all watches: they cause the skin on my wrist to break out.
• The Oura Ring needs to fit exactly to function properly. It’s expensive to buy and expensive to maintain. I wouldn’t wear it during the day because it’s too clunky for my taste, so its daytime sensing features are irrelevant for me. And for night use, the ring doesn’t deliver benefits that are superior to other options.

Studies have shown that all the devices and apps excepting polysomnography have approximately the same sensitivity, accuracy and specificity. And in all cases, their performance  (in my opinion) is rather mediocre. Therefore, the results must be taken as suggestive and relative rather than definitive.

Since performance is so similar for all sleep sensing approaches, I found it easy to choose the SleepScore app for my personal test:

• Since it’s non-contact, it’s not physically intrusive.
• Since it’s distance-specific, it measures only my sleep symptoms, not confusing them with Nola’s on the other side of the bed.
• Because it uses sonar for ranging, not radio waves, I consider it safe for regular use.

Whatever you think about my theory of sleep, the data strongly suggests that getting good sleep is good for long-term brain health. So you may enjoy my in-depth review of the SleepScore app in the next and final blog of this series.

Image Credits:
Counting Sheep, and Crescent Moon – Colour, both from j4p4n via openclipart