I might be in a higher risk group then: I can drink at most 1 coffee per morning (I love coffee but coffee doesn't love me). In addition, the only anti-allergy pill that works for me is a first generation allergy medicine (chlorpheniramine) that's strongly associated with increased chance of dementia. I could stop taking chlorpheniramine, but then my nose would keep me up at night, and poor sleep is also associated with increased chance of dementia.
So I am hoping there are confounding factors in all these studies, such that it's not coffee per se that helps with dementia but rather something along the lines of "the type of person who desires coffee is less likely to develop dementia".
I am curious(because I get stuffed up a lot also) Do you know what is causing your stuffiness?
I know HN hates anecdotal health advice.. especially natural stuff.. but order yourself some Stinging Nettle powder or grounds, loose, and make yourself a decently strong tea everyday. I personally drink a liter, but I've had friends helped by just one cup daily. I had strong seasonal allergies that for 3-5 months of the year would leave me in sneezing fits, or drooling liquid out of my nose, or just with a constant itch in my nose. After years of stinging nettle drinking, on the worst days I have small symptoms. A skeptical friend was finally convinced when we went hiking in an area that started to even bother him, someone who had almost no allergies ever, yet I had half of his reaction.. and he had known how sensitive I was prior.
Obviously there are many types of allergies and who knows if it works for you.. but worth a shot.
In case you haven't read it, I can recommend https://www.press.jhu.edu/books/title/12216/my-house-killing... for ideas on what is causing your allergy.