Normal, cognitive changes as you age are completely normal. This may include mild cognitive impairment, which is quite common in humans after midlife. Usually this "dulling of the mind" starts around middle age. Since the average person lives to about 80 years old, this means that if you’re 40, you are middle age. Even if you are nowhere near 40 right now, this age comes sooner than you think because time passes very fast while you’re living it. Working on keeping your mind sharp as you age can and should start from a young age. The younger you start, the better. However, even if you’re over middle age right now, and even if you feel as if you have less mental dexterity than when you were younger, you can still implement what you will read in the pages that follow. If you do, you may avoid suffering too much decline, keeping your mind as sharp as possible and even improving where you can.
An excellent overview of things that help you stay sharp
This walks you through a variety of things you can do to keep your mind sharp. It covers eating and sleeping habits that will sharpen your mind. It also covers activities that will help such as walking doing puzzles and reading among other things. It is worth reading.