I have never heard of the link to Benadryl, unless they are taking benadryl to "help" with sleep.

In your deepest sleep, there are bursts of brain activity called Slow Wave Oscillations. These have a strong impact on memory consolidation, as well as the clearing of amyloid (beta-amyloid) plaques (think of them like cholesterol in your veins, but amyloids are in your brain).

If you don't get enough deep sleep, and therefore reduce the SWOs, you get a buildup of amyloid plaques.

As we age, we get less deep sleep, less SWOs, you can see where this is going.

It isn't "overactive thoughts" specifically, but again, if you're not getting enough deep sleep due to anxiety I suspect you'd see the same result - but I haven't seen research on that specifically.

However, there is also the issue of us generally having high cortisol levels due to constant fight or flight. There is some research that shows that these high cortisol levels keep our brains in lighter levels of sleep, and therefore reduce deep sleep, making us feel more tired, and damaging our brains. This is connected to the "tired and wired" phenomenon.

It's really a fascinating area.

Thanks for replying. Here is one among many, and I'm a bit surprised you hadn't come across it yet - https://www.health.harvard.edu/blog/common-anticholinergic-d...

Are you saying the drug prevents slow wave oscillations?

The main reason for my whole position is that my wife's village believes people who have an 'over-active' brain get dementia, and can all name examples. They have nothing like benadryl there.

Wow, that is fascinating. The reason I likely haven't come across it is that my interest/research with regards to dementia is sleep specific. I'll definitely be keeping my eyes open for more acetycoline in the further research I come across. Thanks for bringing that to my attention.

I see where you're coming from re: "over-active" brain, and so I'd question if they're equating "over-active" with "reduced sleep", and if there is a commonality there.

I'm not a neurologist, I come from a software engineering background. I've always had an interest in neurology, and got into the sleep-tech field because I've always been an insomniac and started learning more about sleep.

Yeah I listened to a podcast recently about sleep, and how 'sleep' medications such as Ambien are only a partial method of inducing sleep, more like inducing unconsciousness and thus it changes your sleep architecture and prevents you from entering the proper deep sleep cycles. Wouldn't be surprised that benedryll has a similar problem if you use it to help you sleep and not just as an anti-histamine that you stay awake throughout.

https://www.peak-human.com/post/dr-kirk-parsley-md-is-sleep-...

The correlation between amyloid plaques and Alzheimer's has long been known, but how well established is the causation? All of my information is dated, but last I read, causation still hadn't been conclusively established.

Do you have any books to recommended to someone that wants to focus on improving their sleep?

If I did, we wouldn't be going this challenging and hi-tech route :)

You can try all the sleep hygiene stuff you want, but if you're not improving the neurological function of your brain while you sleep, you're not improving the effectiveness of sleep, and since your natural ability to sleep degrades as you age...

The Oxford University Neurology of Sleep textbook is surprisingly approachable. Most people start with Dr Matthew Walkers, Why We Sleep. There are websites dedicated to tearing apart his science, but that goes a bit far. The guy does an excellent job of bringing the importance of sleep to light, and explaining the basics. He also owns up to the "mistakes" or things that have been learned since the book was published.

Had a conversation with a psychiatrist about this recently. The correlation is not between Benadryl exactly, but a class of drugs called anticholinergics of which Benadryl is one. Specifically, there is only a causal link between specific types of anticholinergic drugs (antidepressants, antipsychotics, antiparkinson, bladder antimuscarinic drugs) and not all anticholinergics - Benadryl doesn't fall into any of the categories I just mentioned. Specifically, the largest study (in terms of sample size) showed that there only a slight increase in your odds of getting dementia (6% higher odds) for people older than 55 after taking < 1095 total daily standard doses for over three years (for Benadryl, that's 25-50 mg daily)[1]. That's already a reasonably high dose.

This and other studies have not found correlations between antihistamine anticholinergics and dementia.

[1]: https://jamanetwork.com/journals/jamainternalmedicine/fullar...