It's a no-brainer: no pills, no side effects from meds. Just exercise!
Over five years of research, older adults who did not engage in moderate to high levels of exercise experienced greater declines in cognitive processing speed and memory function. This decline was the same as would have been expected with 10 years of aging instead of the 5 years that actually past in the study.
PositiveTip: Stay active as you age. It is essential for brain health!