★★★★★
Selenium is also an important factor, all alzheimer's patients tested had low levels of selenium.
Most noteworthy is that pigs get a "form" of alzheimer's called encephalomalacia and the historic vetrinary treatment was vitamin E and selenium. Encephalomalacia in pigs is generally associated with a virus, but that may be a result of deficient levels of selenium, an extremely important mineral for the immune system.
Dosage: Vitamin E 1500iu daily, Selenium 400mcg daily.
400mcg is approx 330% of the RDA, and 1500 IU is about 5000% of the RDA. They are both safe at these dosages. Megadosing with vitamin E was only found to be problematic when supplementing with just one form. When the various forms alpha, gamma, delta... of vitamin E are taken together in fairly large dosages there are only benefits.
Take a good multivitamin/mineral supplement (the best and most complete you can find) along with the vitamin E and selenium.