Brain-stimulating activities at any age may preserve memory
New research indicates that reading books, writing and participating in brain-stimulating activities at ANY age may preserve memory. People who participated in mental activity both early and late in life had a slower rate of decline in memory. In fact, mental activity accounted for almost 15% of the difference in decline (between the brains with and without cognitive decline postmortem) beyond what is attributed to tangles and plaques in the brain.
http://www.sciencedaily.com/releases/2013/07/130704094454.htm