its not on annas archive so i couldnt read the full article, but from the abstract it doesnt look like they adjusted for body weight or economic factors.

people trying to lose weight will replace sugar with sweeteners and a lot of cheap soda brands use them to save on costs. poverty and obesity are both associated with dementia and worse health outcomes in general.

XKCD: https://xkcd.com/882/

I still don’t understand how people can consume these diet/no sugar drinks. They taste absolutely terrible.