"Over time, it really intensified," Janis Mara says. "I wanted to think I was just getting older, but my fear was that it was Alzheimer's." Janis Mara's comment over memory suggests that this situation is quite common in old people. Thes senior moments of memory loss are the result of a decline in brain activity that shows up in your 50s and affects most people older than age 65, according to Kirk Erickson, a psychology postdoctoral research associate at the University of Illinois who studies the relationship between memory and lifestyle. Erickson recommends these tactics to help keep neurons, nerve cells in the brain, humming, and reduce the chance of memory loss. Aerobic training increases the supply of blood to the brain, spurs the development of new neurons, and forges more connections between them. All it takes to benefit is 45 minutes of moderate aerobic exercise, such as walking, three times a week. According to analyst reports and surveys, the effec...