a 21 year study of senior citizens recently published in the NEJM looked at what type of activities helped stave off dementia. it turns out that dancing had the greatest benefit in reducing the risk of dementia.
here's a write up on the study:
http://socialdance.stanford.edu/syllabi/smarter.htm
here's the study itself:
http://www.nejm.org/doi/full/10.1056/NEJMoa022252#t=articleTop
We don't know what our limits are, so to start something with the idea of being limited actually ends up limiting us.
Ellen Langer