An interesting Alzheimer's study done a few years ago tracked a group of nuns from the time they went into the convent until their old age. By comparing their entry biographical essays written when they were teenagers with their mental health in old age it was shown that the young women with the largest vocabularies and most inventive imaginations were the least likely to show symptoms of Alzheimer's, while the ones with small vocabularies and dull imaginations had the highest incidence of Alzheimer's in old age.
It begs the question, though..did the verbal, imaginative ones tend to use their brains more throughout their lives?
The matter what your age, it doesn't hurt to keep exercising your brain!