Questioned caffeine , not really, the world lives on caffeine. Probably the most used drug ever, and problems will have shown up.
My mother is 92 and drinks coffee all day long right up to bed time.
My wife rarely drinks any type of caffeinated beverage, she gets a little hyper even from green tea.
I drink a lot of caffeine, but try to limit it after 2:00 PM least it affects my sleep.
I have ADD, so that is likely why I like stimulants and am not adversely affected by them. If I got a prescription for ritalin maybe I would give up caffeine.
Do aerobic exercise, that should increase blood flow also.