Dementia is either Vascular, (caused by gradual narrowing and closure of small brain vessels, or
by very tiny clots blocking very tiny vessels over a long time), or Degenerative, which is premature
breakdown of brain cells( Alzheimer's ). There are less common causes such as trauma, toxic
exposure etc.

       Aspirin works by preventing clot formation, thereby protecting against heart attacks, strokes
and vascular dementia ( caused by very tiny clots that over time reduce brain function ).

       Ibuprofen or NSAIDS in general were recently found to help prevent degenerative dementia
( Alzheimer's ) if taken in small amounts over long periods of time. But Ibuprofen also negates
some of Aspirins beneficial effects cited above.

      To prevent both vascular and degenerative dementias whether with low dose aspirin alone
or in combination with a low dose NSAID is not clear, and I suspect won't be for some time.