... participation in cognitively demanding leisure activities in late life may provide protection against dementia,
Determining the relative contributions of genes that confer risk and environmental factors such as effortful mental activity to the pathogenesis of dementia remains an important but unrealized goal in research on dementia. In the meantime, seniors should be encouraged to read, play board games, and go ballroom dancing, because these activities, at the very least, enhance their quality of life, and they might just do more than that.
Use it or Lose It - Do Effortful Mental Activities Protect against Dementia?
New England Journal of Medicine 2003; 348: 2489-2490
Chess and Dementia Index