Researchers reported seeing a 30 percent to 54 percent reduction in the incidence of Alzheimer's disease in people who regularly consume the erectile dysfunction drug.
This really speaks to Alzheimer's and other brain problems being due to inadequate energy delivery. The primary mechanism of Viagra increases blood flow throughout the body, which means energy can cross the blood brain barrier more easily.
I can only speculate, but I imagine the levels of insulin resistance in the general population, mean the brain slowly starves of energy over time. This is an interesting way to improve things.
There is in no way sufficient evidence in this study to draw this conclusion. This study was in no way designed to provide causal evidence. At best, what we can say is that the people who tend to take sildenafil also are less likely to have alzheimers. It could very well be that the people who take sildenafil are more active, and that activity level staves off alzheimers. Or any number of other third variables. This is not as big a deal as the article is making it out to be. Spurious correlations happen all the time, and it behooves us to be measured in our excitement.