If you do some research and get interested in exogenesis ketones here is one I just ordered yesterday to experiment with. I have used Dr Boz brand and in years past have used a couple of different MCT oils. The MCT oils will raise ketones and Mary Newport had good luck with her husbands dementia at first using coconut oil (only small amounts of MCT's) and later MCT oil as it became available. Exogenous ketones have become available fairly recently as esters and have been around as salts.

I have never used the salts but have used both C8 and C8-C10 blend MCT oils. Have used one brand of ketone ester.

You will have to do your own research but anecdotal evidence is very common for it helping dementia patients. It is thought that the brain does not function properly any more on glucose and is actually low on energy (even though there is plenty of glucose in the blood it for various reasons is not being utilized properly by the brain). Ketones are also brain fuel and it has been shown actually are preferred by the heart and brain and both will utilize ketones if they are in the blood stream.

I know nothing. Do your own due diligence. In my farmer opinion fueling the brain with something other than glucose it is worth investigating. I am not recommending this but I ordered some for myself to try and experiment with. It is a very new offering I was put on to by a doctor I have a lot of faith in. It is not cheap.

https://www.americanketone.com/?syclid=c2b5d531-1e0f-4f3e-a568-cc99b3921f9f

Edit: Here is a study on the above ketone supplement. This is pretty new stuff so not a lot out about it. This study in the last part of it kind of goes over the various forms of ketone supplements and their differences. 
https://nutrition.bmj.com/content/early/2023/07/05/bmjnph-2023-000672

Edit: Here is a brand I have tried and used. I can verify it will raise ketones in the blood because I measured. I am not crazy about Dr Boz as she gets a little carried away with her procedures and selling stuff to support her procedures. A little too sales oriented to suit my taste. That said, the reason I tried it is I have a very good friend with advanced Parkinsons. She takes exogenous ketones and it really helps her control her Parkinsons (along with a ketogenic diet). She has tried several different brands and forms and said this one worked the quickest and raised her ketones the most. So I thought I would give it a try and I did.

Dr Boz Pucker Up

Exogenous ketones are not something I am going to take all the time or even part of the time. They are expensive and I don't think I need them in any way. The reason I am trying some of them is just to get experience about their effects and our tolerance to them. I figure it is better to explore them before we need them instead of having to try and do it when we may already be impaired. Crazy idea??? Probably. Will not be my first one nor probably my last. If wife or I do run into cognative problems as we age (70 now), I want to be prepared to do something about it. Spending a little money now for experimentation is not a big deal for us. Athletes use the stuff so I think it has been proven safe enough for me to not worry about the safety aspect.