I don't know it for a fact but just know that it is true: the increase in AD is related to the anti-fat, anti-cholesterol, anti-animal-based diet stance of "experts" and governments. Human brains are 60% fat and thrive on cholesterol. Eating animals it what made our species' brains grow bigger and smarter. My brain is sharp as a tack when I eat very low carb real foods and plenty of animal protein. Plant protein gives me brain fog. Inflammation, allergies and intolerances are often the reactions to the body sensing "foreign" proteins that it needs to attack or encapsulate. So why would we want to turn our diet 180 degrees around from the foods we were designed to eat?