New research hints that even simple exercise just might help seniors with mild memory problems. While physical activity helps keep healthy brains fit, it’s not clear how much it helps once memory starts to slide. The U.S. study compared sedentary older adults assigned aerobic exercises or a simple stretching routine, along with group classes and instructors to keep them engaged. A year later, brain testing showed neither group experienced the decline that’s usual with so-called mild cognitive impairment. Experts caution more research is needed. The early findings were presented Tuesday at an Alzheimer’s Association meeting.