Science

All valid questions I'm curious about myself, but from my cursory look at this specific study, they only took a very broad look at vegetable intake involvement, specifically along the lines of "Does the reduction in dementia risk hold true even for people with a high veg vs low veg diet?"

So even if your hypothesis seems reasonable, I'd hesitate to make any assumptions without research backing it up. Not to mention I don't even know if the present study even holds water, considering the number of such studies that end up being 'tabloid' level research.