We all know walking offers a range of benefits. But did you know it might be good for your brain, too? A new study shows that people who walk regularly tend to keep their brains large and healthy.

Alzheimer’s disease is not well understood, but doctors have long understood that dementia is accompanied by some degree of brain shrinkage. The study, published in this week’s issue of Neurology, measured brain size as an indicator of cognitive health in a group of about 300 seniors.

The participants, whose average age was 78, were tracked over 13 years. They were surveyed on their walking habits, which ranged from zero to over 30 miles per week. After nine years, they underwent an MRI scan – a medical procedure for imaging the brain. Four years later, they were tested for dementia.

The results showed that the folks who walked the last had the most brain shrinkage and associated cognitive impairment. On the other hand, people who walked more were significantly less likely to show this decline – up to half the risk for those who walked six to nine miles per week. More miles than that did not seem to offer any extra protection.

How might walking confer these benefits? That’s no less mysterious than Alzheimer’s disease itself. But since getting up and moving around increases blood flow to the brain, researchers speculate that staying active keeps your cranium flush with a healthy supply of oxygen and nutrients. It’s not clear that this affects the root cause of dementia, but it may well be a strong defense against the symptoms.

It’s important to note that this is an observational study. It’s still possible that some other factor makes people both walk more and stay in better brain health. But for now, the researchers are assuming otherwise. According to the study’s lead author Kirk Erickson, “Our results should encourage welldesigned trials of physical exercise in older adults as a promising approach for preventing dementia and Alzheimer’s disease.”

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