You're right about that article Progecitor and I was wrong (I should have read it a little more carefully). Thanks for the clarification.
Nonetheless, as far as I can tell, most research on this subject theorises the opposite of that article ie. they typically theorise that thiamine protects against cognitive decline. Two examples below:-
https://pmc.ncbi.nlm.nih.gov/articles/PMC9585656/
https://pmc.ncbi.nlm.nih.gov/articles/PMC4846521/
Re anal itching, I don't think I have prostatitis as I don't have any of the symptoms of that condition. That's good if you've managed to treat it. I could be wrong but I think mine is probably a symptom of pois.
Regarding thiamine I also often bump into contradictory studies, so hopefully it is as you say.
Regarding the itching I meant to say that it is primarily due to POIS for me as well, but lately it wasn’t so bad as it used to be. In the past 20 years before beginning to treat myself with anything it was quite brutal at times. Just yesterday I had an O and about an hour later the itching began. This is also the time when my eyes tend to deteriorate the most rapidly. Nevertheless it had become hardly perceptible just a short time later probably due to the medications I take. However in the past it was an almost incessant feeling, which had driven me crazy. I remember that at those times I had been much more susceptible to sexual stimuli, and merely fantasying about women even just for a short time would lead to the dripping of some precum. After that the waves of unrelenting itching were inevitable. Of course this may be regarded as an inconvenience, but it also clearly shows that something is really wrong. Later I also realized that there were times when I had no sexual activity, but the itching would still surge. This was clearly caused by dietary elements, that were really hard to figure out as this only happened several hours after the actual meal, that was often varied. One thing that absolutely caused this was coffee, which I drank in a daily manner in great quantity. Exercise intolerance can also elevate this symptom, though it does not happen right away, but only after I reach some point in the exertion, then it progressively gets worse. If I don’t stop working then after a while it turns into a bad burning pain actually. Being simply tired can also elevate this symptom as it tends to be a common occurrence a few hours before going to bed. When it occurs that is when my eyes also begin to get really dry and hurt. On a few occasion in the past I also experienced a few episodes of what I call superPOIS. It seems to happen when I remain awake more than 22 hours or more and at one point this itchiness becomes very-very strong without pause. At the same time I also get very cold and unwell. I remember that it was a hot summer day and my teeth were clattering and I was shaking under the blanket as I felt like I was freezing and of course there was the crazy itchiness at the same time. Then I slept several hours and woke up feeling just alright. This thing happened at least 3 times and I have no mood to try it again as it felt like my body was collapsing.
Thus the itching is clearly due to POIS, but other factors can also interplay in determining its actual strength. It is also clearly correlated to the intensity of the anal burning, which is due to the inflammation of the rectum. And the only logical association to sexual activity is that it is due to the inflammation of the prostate, ergo prostatitis. Of course I also had other ideas in the past like there was a time when I was convinced it was caused by some parasites or worms and I went to the lab many times to prove it. However after a while I had to accept the truth of the many negative results. Of course I was also at the Urology, but they have never found anything wrong and told me that it can’t be anything serious, thus they only advised me to drink some herbal teas. I actually did so, however they hardly ever did anything significant. I only wish I knew the term POIS, so I could have told them how wrong they were, but all I could do at the time was to remain silent and accept how stupid I was.
If you can’t feel the burning pain, but only the itching, then it shows that the inflammation is only moderate at best and did not reach a critical threshold to turn into actual pain. Of course this doesn’t mean that you would not develop systemic symptoms as the inflammation would still spread as a dilution process. The supplements I mentioned were only a few examples, however I believe that technically almost all supplements on the market work to some degree and even those herbal teas that were recommended by my doctors are beneficial. However the real question was always the one of efficacy, as the POIS inflammation is so strong that even combinations of supplements can barely do any significant change. And I don’t even want to mention drug resistance, which makes almost all effort a futile attempt.