Brisk, older walkers live longer.

Research just doesn't come any simpler than that, and University of Pittsburgh researchers say there's evidence that the ability to walk well is a powerful sign of healthy aging overall.

The researchers, professor of medicine Stephanie Studenski, assistant professor Subashan Perera and research data analyst Yazan Roumani, presented their findings Friday at the national meeting of the Gerontological Society of America in San Francisco.

They used measurements of walking speed from data collected in 1996 from about 500 participants in Kansas City, Mo., where Dr. Studenski formerly worked. National mortality information enabled the researchers to check nine years later on whether the people were still alive.

They found that 27 percent of people deemed to walk at a fast speed -- at least 1 meter per second from a standing start, or roughly 2.5 miles per hour when adjusted over a longer distance -- were dead nine years after they were first measured. Meanwhile, 77 percent of those evaluated as walking slowly -- about 1.5 mph or less -- had died, as had 50 percent of those at medium speed.

Dr. Studenski, a geriatrician, said in an interview that the importance of walking speed is quietly noted by many people.

"I'm struck by how many families will bring an older adult to my clinical care worried that mom is slowing down, and the whole family observes mom is slowing down," she said.

"I think there's very rich lay awareness that how people move is an important sign of how well people are doing as they age."

Even when accounting for disparities in the 65-and-older population's diseases, ages or other health-related factors, there's still a significant difference in mortality based on walking, Dr. Studenski said. And whether they're slow or fast walkers to begin with, any tendency to increase speed naturally over time rather than lose it is also tied to their survival rates.

Dr. Studenski said the explanation for the findings could be that walking is influenced by so many vital parts of the body: heart, lungs, bones and nervous system. If those are serving a person well enough to enable him or her to walk briskly, it's typically a sign they're functioning well enough to help provide years more of good health.

"The interesting thing about walking speed is each person picks what's best for them, and it's amazingly stable," the professor of medicine said. "For those whose health is stable, it will be the same over and over again, and when a person's walking speed changes, it's generally because of some change in health, and in some of these things like the heart and lungs and other things that affect walking speed."

Dr. Studenski said the findings, which have yet to be published, aren't intended to encourage older adults to begin walking faster.

Rather, the individuals, families and physicians would be smart, she said, to measure walking speed now for a baseline. They could use it as a guide later to help assess whether a person is slowing down and thus might be having health problems that would otherwise go undetected.

"It's like a vital sign," she said, "just like if somebody had a fever or high blood pressure, it would be an indication we should look into this."

While some deterioration in most people's abilities occurs as they age, it varies greatly for everyone, Dr. Studenski said.

Neither the aging process itself nor the person's list of diseases will necessarily reflect what they're capable of.

The gait study is one of about 60 that Pitt researchers are presenting on various aging-related issues as part of the national conference.