Keep your mind sharp with a 30-minute workout.

Find a form of exercise that you enjoy, and do it almost every day.

RODALE NEWS, EMMAUS, PA—People who want to keep their brains sharp might consider investing in gadgets that claim to lower your brain age or go back to school, but it could be that a simple daily workout would be just as helpful. A new study published in the Archives of Neurology has found that older adults who exercised regularly were at a lower risk for mild cognitive impairment, a precursor to dementia, than people who were more sedentary. And while it's true that the earlier you get started, the more you'll lower your risk, even people in their 70s seem to benefit by exercising.

THE DETAILS: The researchers used a sampling of 1,324 adults who were either between the ages of 70 and 79, or 80 and 89, none of whom had been diagnosed with dementia. Each participant underwent brain scans and psychological evaluations to see if they suffered from mild cognitive impairment. Then the participants filled out questionnaires reporting how much exercise they got in the year prior to the psychological tests, as well as how often they exercised when they were between the ages of 50 to 65. The researchers found that people who'd engaged in moderate exercise, such as brisk walking, aerobics, resistance training, yoga, and swimming (to name just a few), five to six times a week during their 50s and 60s saw the best results—a 39 percent reduced risk of having mild cognitive impairment during their 70s and 80s. But even people who got daily moderate exercise later in life saw a reduced risk of 32 percent.

Read on to learn how exercise improves mental functioning.