This is consistent with 27chaos's statement, though. If you get a body transplant at 65, you have solved a number of medical problems, and the chance of living the next 30 years without having to worry about Alzheimer's is ~70%. Of course, Alzheimer's disease accounts for only 60-80% of cases of dementia. But still, I think there would be a market.
It is also worth noting that cardiovascular factors, physical fitness, and diet contribute to the risk of dementia, including Alzheimer's. These are not the greatest risk factors (as you might have guessed, age is the greatest risk factor), but these can be managed if you are motivated to do so -- in fact, getting a new body should be a fairly effective way of managing cardiovascular fitness.
If you get a body transplant at 65, you have solved a number of medical problems
You also add additional medical issues that come up with transplantation. Likely you won't get all nerves to be perfectly lined up.
Another month, another rationality quotes thread. The rules are: