As for #11, Non-flossed teeth are a material source of inflammation in the body. Inflammation has been shown to be a significant driver of several health conditions [1] including arterial clogging (ie, that cholesterol itself only starts to "stick" in the presence of inflammation). Arterial clogging is an issue in the brain as well as the heart. Poor dental hygeine is correlated with heart attacks, for example.
Avoiding simple carbohydrates (#1) is primarily important to control blood sugar (elevated blood sugar has many detrimental effects, both short term and long term [2]). But fructose and alcohol, also simple carbs, are metabolized by the liver and the metabolic by-products are shown to cause inflammation as well [3]
Basically, people with poor oral hygiene are more likely to develop Alzheimer's than people with good teeth.
You might have heard about a similar study that found a link between oral hygiene and heart disease. The theory, at least in that case, is that bad oral hygiene causes chronic long-term inflammation throughout the body, not just in your gums. This might increase risk of heart disease. Without looking at the data, I would guess that the same theory applies to Alzheimer's and maybe other diseases. The usual caveat about correlation != causation applies of course.
?? If Alzheimer's is related to memory & executive functioning(probably is) then the people who are likely to develop Alzheimer's are likely to have poor oral hygiene.
Oral hygiene is a good proxy for people who know it's important, but somehow still forget. A solid proxy for executive functioning decline, executive functioning in general, working memory, and a cluster of other things.
There is a link between dental hygiene and cognitive function. This is caused because bad dental hygiene leads to a bacterial infection in the mouth which in turn leads to large amounts of inflammation which damages the brain in addition to the cardiovascular system.
