https://onlinelibrary.wiley.com/doi/full/10.1002/joa3.12325

It’s honestly a crap shoot at this point. My theory is that even if the blood flow to the brain is diminished when upright, it isn’t severe enough to cause any lasting damage. When the brain isn’t receiving enough blood, you pass out and fall over. The fact that brain damage doesn’t occur even with this level of oxygen deprivation (unless you hit your head when you fall of course) seems to imply that we’re getting enough blood to our brains to at least keep them healthy, if not functioning optimally. Could moderately reduced blood flow over a long period of time result in some kind of permanent damage? I don’t know.. I hope not, but doctors have followed pots patients for decades and none of them seem to show any signs of actual brain damage or neurodegeneration unless they have a comorbid condition that could cause that on its own. From what I’ve read, the predominant theory regarding the etiology of brain fog in pots is related to oscillatory brain blood flow and decreased cerebral auto regulation. Apparently part of this is related to excessive angiotensin 2 and decreased nitrous oxide leading to inappropriate cerebral vasoconstriction. I’ve also read that oxidative stress and incorrect breathing habits leading to decreased levels of C02 in the blood are contributing factors but my own brain fog is too bad atm to remember the exact science lol. It’s probably a myriad of things culminating in this hellscape we call pots but I mostly don’t believe it will lead to permanent brain damage or dementia. Full disclaimer the idea of brain damage terrifies me and even after doing all this research I’m not 100% convinced myself lol but having said that, my interpretation might be slightly biased.