I ran across this article on the mechanism behind statins causing cognitive decline a couple years ago. I did a little more digging and didn't find a whole lot of new info on the subject so it may have turned out to be a dead end or maybe it's accepted and everyone has moved on to other studies.
https://news.arizona.edu/story/research-reveals-possible-reason-for-cholesterol-drug-side-effects
The good news is that mental fuzziness disappears after the person stops taking a statin. (Speaking from personal experience!)
When I was working with my gastroenterologist on my liver enzyme reaction to Rosuvastatin he said that all statins work pretty much the same way and if you have a bad reaction to one of them you'll likely have a bad reaction to all of them. While he was referring to problems with liver enzymes this may be true for mental fuzziness as well.
Since my liver enzyme problem had been solved and my mental fuzziness had disappeared (which I only detected by it's absence) I stopped looking into the topic any further. There may be more recent journal papers that have newer data on this subject.
One of the interesting things about the medical world is that the vast majority of medical papers I've read have had the same basic format.
1) We tested xxxx number of people with half being given a dose of magic stuff and half given a placebo.
2) The results are magic stuff works in yyyy number of cases and the placebo had the same effect on zzzz number of cases.
3) Therefore it's reasonable to conclude that magic stuff is/isn't a viable solution.
That's pretty much it. Engineering and scientific papers where the laws of physics are pretty well understood always frame the problem within these laws and show how it holds without exception in every case. This gives a solid foundation for further work to be done with reasonable certainty.
My guess is that this difference is due to the fact that the physical mechanism behind biological systems has yet to be comprehensively established in such a way that the phenomena being discussed can be accurately and irrefutably quantified in every case. The medical world is still in the empirical phase of understanding. How long will it take for them to REALLY understand biological systems so every cause and every outcome can be accurately identified? Probably quite a while. A century or two?
I've never heard of a blood test or some other quick and inexpensive method for assessing the presence of "beads on a string". Seems like this would be a useful test for those people who would like to keep all their wits about them.