LOS ANGELES – Walking may put the brakes on cognitive decline in healthy older people as well as those with cognitive impairment, a new study finds.

The ongoing study, which spans 20 years, also quantified how much walking is necessary to keep brain volume up.

Researchers followed 426 older adults for a number of years to see if there were changes in brain volume. Among the participants 299 were healthy and 127 had cognitive impairments, including 83 with mild cognitive impairment and 44 with Alzheimer’s disease.

The more people moved, the higher their brain volume, a marker for brain health. That link held after adjusting for factors such as age, gender, body mass index and education. People who met the requirements for activity also scored better on a mental exam.

For healthy adults, walking at least 72 blocks a week (about six miles) can preserve brain volume and slow the risk of cognitive decline. Cognitively impaired adults needed to walk at least 58 city blocks a week (about five miles) to achieve the same results.

“Because a cure for Alzheimer’s is not yet a reality, we hope to find ways of alleviating disease progression or symptoms in people who are already cognitively impaired,” said study co-author Cyrus Raji, in a news release.

The study was presented recently at the annual meeting of the Radiological Society of North America in Chicago.