Alzheimer and dementia are cardiovascular diseases. ED (erectile dysfunction) is also a cardiovascular disfunction, and also refered to as the "canary in the coal mine" pertaining to bigger cardiovascular issues in men. The arteries of the penis and brain are so tiny they are usually affected first. The trouble with preventing/reversing ED and dementia is a complete overhaul of diet which most people won't do. Check out the video for the science.

https://nutritionfacts.org/video/how-to-prevent-alzheimers-with-diet/