Walking just two or three hours per week may lower women’s chances of developing dementia, researchers at Harvard found.

The study at the Harvard School of Public Health (HSPH) and Brigham and Women’s Hospital was published yesterday in the Journal of the American Medical Association.

The National Institutes of Health website characterizes dementia as the “significant impairment” of memory, reasoning and judgment.

“Age-related dementia is often preceded by small declines in cognitive function,” said Jennifer L. Weuve, a research fellow at the HSPH who conducted the study. “Memory, the ability to learn and the ability to focus—those are things that start to diminish in the early stages.”

While walking two or three hours at 20 minutes a mile was associated with better cognitive ability, the study found that “the most consistent benefits were associated with physical activity on the order of six hours a week at an easy pace,” Weuve said.

The study found that women who performed these types of activities had a 20 percent decrease in their risk of cognitive impairment.

“It’s further evidence that exercise is good for your health,” said Francine Grodstein, the associate professor of medicine at Brigham and Women’s Hospital and Harvard Medical School who sponsored the study. “I think that’s the most important part...this is a way to reduce early stages of dementia development.”

Researchers followed approximately 1,800 women who were in their 60s and 70s for over a span of 10 years.

“Starting from the mid-80s, we periodically asked them about their participation in physical activities such as walking, swimming and aerobics,” Weuve said.

The women were also given tests of their cognitive function over the phone. According to Weuve, women who scored better performed more strenuous and extended physical activity than those who did not.

Robert D. Abbott, a professor of biostatistics at the University of Virginia School of Medicine, said that Weuve and Grodstein’s study corroborates his results, also published in this issue of JAMA.

“[Weuve and Grodstein’s] study is with women—ours is with men,” said Abbott.

According to Abbot, men who were 71 to 93 years old and walked less than one-fourth of a mile per day were nearly twice as likely to develop dementia as those who walked more than two miles a day.

“We suspected that what we found wasn’t limited only to men and probably also extended to women,” Abbott said. “Dr. Weuve’s paper seals that very nicely for me.”

—Staff writer Risheng Xu may be reached at xu4@fas.harvard.edu.