Caffeine has both good and bad effects, both of which may impact on cognitive performance.
Coffee contains active ingredients other than caffeine which may, directly or indirectly, impact on cognitive performance.
Caffeine appears to be of greater potential significance to older adults.
However, those with hypertension, diabetes, impaired glucose tolerance, or high homocysteine levels, would be wiser to avoid coffee, even if decaffeinated.
Caffeine's main impact is on attention.