We often talk about fitness for our body, but our brain is just as important to take care of. While it's shown that memory loss is a given with aging, we can do a lot to improve the brain's function. According to an article in Martha Stewart, Living magazine, diet plays a big part in brain health. Include berries, leafy greens and cruciferous vegetables in your diet. Omega-3 fatty acids help to fight inflammation which can also affect the brain - fish, nuts, olives, avocados.
Other suggestions are to get plenty of sleep (8 hours), limit screen time which makes concentrating difficult and exercise regularly.