especially if you already have an active lifestyle

There's no need to attack me so hard

Iirc the causality is thought to be about opening vesicles and increasing blood flow in the brain.

My guess is that people who regularly drink coffee are supporting some sort of regular mental activity, like a job or school.

Could be due to fiber. Reduce cholesterol, improve gut health

It's fine to highlight it's correlation, but your guess is a theory of causation. It's likely either some genetic combo that drives the desire for coffee or some lifestyle arrangement that drives the need.

Even the idea that an inactive mind leads to deterioration isn't definitively causation. Correlation goes both ways. Are they mentally healthy because they're mentally active? Or are they mentally active because they're mentally healthy? The degree of mental deterioration goes up as you age, which is also when you can retire, when you don't have to support your family, when you're physically incapacitated, and when you slow down overall. So yeah, I plan to stay active because I'll take my chances that it helps, but at some point, something will simply break. Maybe I'll inherit the dimentia. Maybe I'll inherit the neuropathy. Maybe both. Maybe neither.