Best Life, reporting on findings by researchers at the Medical University of South Carolina, had this to say:
"High cholesterol foods might increase your odds of developing Alzheimer's Disease. Scientists at the Medical University of South Carolina found that mice fed a high cholesterol diet for two months were unable to complete memory tasks and showed significant inflammation in their brains. Tissue samples revealed that high cholesterol foods encouraged the creation of a protein that forms amyloid plaques - the hallmarks of Alzheimer's Disease. Researchers speculate that inflammation in the brain causes immune cells to gather, leading to a buildup of plaques."
Whether you believe that the plaques cause Alzheimer's or merely identify it, there is a growing body of research showing that arterial damage caused by cholesterol, atherosclerosis, hypertension, and inflammation all contribute to amyloid plaque build up. It is hard to argue that decreasing these issues might not help prevent the onset of Alzheimer's Disease.
Conversely it is easy to argue that once Alzheimer's set in it is still an irreversible condition. This is why it is important to do what you can now to decrease your risks and your loved one's risks upfront so that you don't have to deal with the problems associated with Alzheimer’s such as communicating to Alzheimer’s patients or trying to cope with communication issues and memory issues yourself.