Don't miss "At Card Table, Clues to a Lucid Old Age"in today's New York Times: http://www.nytimes.com/2009/05/22/health/research/22brain.html?_r=1&hp
The story reveals new information from research on 90-somethings, especially those who have no signs of dementia. Of course, we'll all be in that pool, right?
Two factors keep showing up as important, if you want to keep those brain cells accessible. One is regular social interaction with friends or family, and the other is the use of grey matter. Wonder if today's young seniors, like us, will benefit from the use of the Internet, which provides both mental stimulation and a virtual social life? Would make an interesting doctoral dissertation, but the candidate might have to wait 20-30 years for the degree.