About half of the study participants were non-vegetarian, IIUC. I wonder if they found any correlation after slicing by vegetarianism?

A core part of the scientific method is that you attempt to isolate a single variable at a time. If anything, all this suggests is that this was a better diet-controlled sample population for measuring the correlation of eggs and Alzheimer's than the general public. That said, the methodology of this study does not allow for inferring a relationship between Alzheimer's and meat consumption in either direction.

Adventists are okay with meat as long as it’s kosher generally.

I think the bigger factor is that they’re teetotalers.

My data points, though: two of my vegetarian teetotaling Adventist family members died of Alzheimer’s. The lifestyle is clearly not a cheat code for defeating dementia.

eggs are a highly concentrated natural source of choline. meat does contain choline but nowhere near as much as eggs.

drawing the connection between cholinergic activity and alzheimers is left as an exercise for the unaware reader.