"Older adults who walk frequently have lower risk for cognitive decline years later, according to an observational study in Neurology.
Some 300 adults aged 65 or older reported how much they walked per week, and then had MRI scans 9 years later. Those who walked at least 72 blocks (6–9 miles) a week had greater gray matter volume on later MRI, compared with those who walked less. In turn, those with more gray matter volume were less likely to have cognitive impairment 4 years after the MRI, relative to those with less gray matter volume.
The authors say their findings "are in line with data that aerobic activity induces a host of cellular cascades that could conceivably increase [gray matter] volume." Still, they caution that their study does not prove a causal link between walking and better cognition."