This is very interesting and timely to me as I've been looking into nootropics to increase my cognitive functions as I feel like I'm getting more forgetful.
Viagra increases blood flow to the heart and I believe to the brain as well? I haven't read the whole article, but I think there is something to this. What stuck out for me by some of what I read is the importance of choline in the diet for memory. Also lowering the homocysteine level is important. It also seems to be important to get more blood flow in the brain.
If Alzheimer's is cerebrovascular disease, then it makes sense that something like Viagra which increases blood flow to the brain is effective against Alzheimer's.
I'm currently looking into citicoline, Alpha GPC, and vinpocetine.
Alpha GPC is a natural choline compound found in the brain. It is also a parasympathomimetic acetylcholine precursor which has been investigated for its potential for the treatment of Alzheimer's disease and other dementias (Wiki).
Citicoline serves as a choline donor for the synthesis of acetylcholine.
In Alzheimer's disease, choline levels decrease; this affects the brain cell's ability to produce acetylcholine, a neurotransmitter important for memory. Brain cells may instead break down cell membranes to produce acetyl-choline, and taking citicoline is thought to prevent this breakdown. (alzdiscovery.org)
Vinpocetine is a man-made chemical similar to a substance found in the periwinkle plant (Vinca minor). In Europe, it's sold as a drug called Cavinton. Vinpocetine might increase blood flow to the brain and protect brain cells (neurons) against injury.(webmd). Evidently, vinpocetine can help reduce symptoms in people whose tinnitus is due to poor blood flow (peacehealth.org)
I'm not a doctor and I am not recommending you will take these supplements. I am just stating what I am looking into and what kind of nootropics I am thinking of experimenting with. Citicoline seems to have a fairly long half-life, so I think I will be careful experimenting with this. I would be very careful with vinpocetine as it's only sold as a prescription in some countries and it will most likely lower my blood pressure just like Viagra probably would.
I started out with Lions Mane mushrooms (another nootropic for memory) - I didn't notice much of anything from them after a few days. I'm planning to take citicoline soon, but I started taking Alpha GPC a few days ago and the effect has been quite immediate and so far, I'm very happy with it. I only take 1/4 of the normal dosage and it works for me surprisingly well (and fast) although it seems to make my dreams a bit too vivid and wild. I think I will just take it earlier in the day.
I have also added back eating more eggs (which are high in choline, a precursor to acetylcholine). And started taking Vit B complex for Vit B12, B6 and folic acid (which is supposed to lower homocysteine levels.) Not sure however if this is doing anything.