Regular physical activity may help older people reduce their chances of getting dementia.

In a new study published in the American Heart Association journal Stroke, older, non-disabled people who regularly engaged in physical activity reduced their risk of vascular-related dementia by 40 percent and cognitive impairment of any etiology by 60 percent.

The protective effect of regular physical activity remained regardless of age, education, changes in the brain's white matter and even previous history of stroke or diabetes, researchers said.

The findings are based on a prospective multinational European study that included yearly comprehensive cognitive assessments for three years. The results are part of increasing evidence that regular physical activity promotes brain health, researchers said.

"We strongly suggest physical activity of moderate intensity at least 30 minutes three times a week to prevent cognitive impairment," said Ana Verdelho, M.D., lead author of the study and a neuroscience researcher at the University of Lisbon, Santa Maria Hospital in Portugal. "This is particularly important for people with vascular risk factors such as hypertension, stroke or diabetes."

The analysis included 639 people in their 60s and 70s; 55 percent were women and almost 64 percent said they were active at least 30 minutes a day three times a week. The activity included gym classes, walking and biking.

The American Heart Association recommends at least 150 minutes of moderate exercise every week or 75 minutes of vigorous exercise for optimal health.

Researchers performed magnetic resonance imaging (MRI) tests at the beginning and end of the study to gauge white matter changes in the brain, an indicator of possible cognitive decline.

"Damage of the cerebral white matter is implicated in cognitive problems including depression, walking difficulties and urinary complaints," Verdelho said. "White matter changes are very common in older people and mainly associated with vascular risk factors like hypertension and stroke."

Throughout the study, researchers asked participants in phone interviews and clinical visits about depression, quality of life and performing everyday activities.

At the end of the follow-up, 90 patients had dementia, including 54 with vascular dementia in which impaired blood flow to the brain causes cognitive decline, and 34 patients met criteria for Alzheimer's disease. Another 147 patients developed cognitive impairment, but not dementia.