Recent scientific studies have shown that “participation in activities that stretch the brain was linked to improved memory, processing speed, and executive functioning skills.” 
Cognitive training does not have to be arduous or boring. It can be fun too!
In fact, research has determined that people who love playing games—crossword puzzles, cards, checkers, etc.—have “better working memory, verbal learning and memory, processing speed, mental flexibility and spatial skills.”
Engaging in mental activity significantly lowers the risk of cognitive impairment and even has “a protective effect against developing dementia.”
The Brain Health Book—J. Randolph