Connections Between Mental Fitness and Walking Have Been Alluded to Since Time Immemorial. New Research Tends to Be Supportive of this Hypothesis. We Covered this a few Years Back in an Article About 10k Steps for Mental Fitness.
...Walking six to nine miles a week may protect brain size. Brains tend to shrink in late adulthood, often leading to cognitive impairment; the stage of memory loss that precedes dementia and Alzheimer’s disease....