As part of their health routine, Anne and Dave Longworth take brisk walks for at least 30 minutes a day.
"I'll be 65 in May. Walking is supposed to good for your heart. It's good for warding off Alzheimer's," Anne told CBS News.
She's right. Studies show exercise like walking can provide protective benefits for the brain. And now new research suggests that how fast elderly people walk may be related to their risk of Alzheimer's disease.
The study, published online in Neurology, the medical journal of the American Academy of Neurology, found that a slow walking speed is associated with higher amounts of amyloid, one of the abnormal proteins in the brain linked to Alzheimer's.
"This study builds on existing data that it pays to be fit," said Dr. Thomas Wisniewski, director of the NYU Langone Center for Cognitive Neurology.
Researchers from France studied 128 people aged 70 and older who did not have dementia but were considered at high risk for developing it because they had some concerns about their memory.
The patients underwent brain scans to measure amyloid plaques in their brains and took a series of tests to assess their thinking and memory skills, as well as how well they could complete everyday activities.
The researchers also measured walking speed with a standard test that times people on how fast they can walk about 13 feet at their usual pace.
The results showed an association between slow walking speed and amyloid in several areas of the brain, including a region called the putamen, which is involved in motor function.
"It's possible that having subtle walking disturbances in addition to memory concerns may signal Alzheimer's disease, even before people show any clinical symptoms," study author Natalia del Campo, PhD, of the Gerontopole and the Centre of Excellence in Neurodegeneration of Toulouse (University Hospital Toulouse), said in a statement.
Researchers have been trying to find early clues that may signal Alzheimer's disease for years in an attempt to catch it as soon as possible and get patients treatment before symptoms progress. Previous studies have suggested a faltering sense of smell and amyloid build-up in the eye -- detected by vision scans -- could also be early signs of the disease.
The authors of this new study note that their research looked only at a snapshot in time and only shows an association -- it does not prove that amyloid plaques cause the slowdown in walking speed. And certainly there are many other reasons that may explain why a person walks slowly.
In other words, if you walk slowly, don't be alarmed. "There are so many causes of being a slow walker which really have nothing to do with brain function," Wisniewski said.
As for the Longworths, Anne worries she could develop Alzheimer's because both her parents had dementia. But so far, she and her husband have showed no signs of slowing down.