Holding off the memory loss and mental decline that comes with age may be as simple as putting on your walking shoes. A study of elderly adults found that walking five to six miles per week slowed cognitive decline. This was true for healthy adults as well as those who were already cognitively impaired, including people with Alzheimer's disease. The study measured both brain volume and memory loss.

Walking isn't a cure for Alzheimer's. But the study suggests that walking can improve the brain's resistance to the disease and reduce memory loss over time, even in healthy adults.

The scans showed that greater amounts of walking during the previous 10 years were associated with greater brain volume. This was especially evident in areas of the brain's key memory and learning centers.

Mild cognitive impairment (MCI) is a catch-all term for persons who have cognitive or memory problems worse than typical for those in their age group but not as severe as those of Alzheimer's disease. About half the people diagnosed with MCI will eventually develop Alzheimer's disease.

The study found that greater amounts of walking were associated with greater brain volume and mental ability. People with cognitive impairment (MCI or Alzheimer's) needed to walk about five miles a week (58 city blocks) to fully maintain their initial brain volume. The healthy adults in the study needed to walk at least six miles a week (72 city blocks) to maintain their initial brain volume.

Because city blocks differ in length from city to city and even within the same city, a pedometer is the best way to measure walking distance. But it's the walking itself that's the important part.

The still ongoing 20-year study included 426 people. 299 were healthy adults, average age 78. The other 127 were cognitively impaired: 83 with MCI and 44 with Alzheimer's, average age 81. After 10 years, all patients underwent 3-D MRI brain imaging to determine total brain volume and the volume of specific regions of the brain. A decrease in brain volume suggests brain cell death and lowered mental abilities.

The scans showed that greater amounts of walking during the previous 10 years were associated with greater brain volume. This was especially evident in areas of the brain's key memory and learning centers. Walking more than the threshold distance (58 blocks a week for the cognitively impaired, 72 blocks a week for healthy subjects) did not confer any additional benefits to brain volume.

Subjects were also given the mini-mental state exam (MMSE), which tracks cognitive decline, five years into the study. The scores of patients who were already cognitively impaired at the start of the study decreased by five points if they had not engaged in at least the threshold level of walking; those who did averaged only a one-point decline on the exam.

These results all suggest that walking is good for the mind.

The results of the study were presented by University of Pittsburgh researcher Cyrus Raji, Ph.D. November 29 at the 2010 annual meeting of the Radiological Society of North America (RSNA) in Chicago. An article detailing a portion of the study appears in the October 19, 2010 issue of Neurology.