It's well worth remembering that regular exercise brings benefits that no present medical technology can match -- and at a fraction of the cost of medicines that do far less.
This Eurekalert! article notes a study in which researchers compared brain scans of older adults who exercise to brain scans of those who do not. They recruited 12 adults, age 60 to 76. Six had participated in aerobic exercise for three or more hours per week over the last 10 years, and six exercised less than one hour per week.
All of the volunteers underwent MRI and MR angiography to depict blood vessels in the brain. Researchers were able to make 3-D models of the blood vessels and examine them for shape and size. The results showed that the inactive group exhibited fewer small blood vessels in the brain, along with more unpredictable blood flow through the brain. The active adults had more small blood vessels and improved cerebral blood flow.