Walking and life expectancy

Walking is one of the simplest, least expensive, and most effective things you can do for your health. It strengthens bones, tunes up the cardiovascular system, and, psychologically, can clear a cluttered mind. Hundreds of studies have documented its benefits, and now, researchers say that later in life, walking becomes as much an indicator of health as a promoter of it.

As we get older, the stroll that was once a walk in the park may get difficult for any number of reasons: angina, arthritis, bad balance, failing vision. Researchers at the University of Pittsburgh have shown that after about age 65, how fast we walk may predict how long we have to live.

Walking, or gait, speed has long been recognized as a proxy for overall health and vitality and has been measured in many research projects. The University of Pittsburgh researchers didn't conduct a new study, but used some sophisticated statistical techniques to pool the results of nine that had already been done. They standardized the disparate ways gait speed had been measured in those studies — no small feat — and then did some further analysis to see how gait speed correlated with how long people lived.

What they found was a remarkably consistent association between faster gait speed and longer life that was true for both men and women ages 65 and older. More precisely, each increase of 0.1 meter per second in gait speed was associated with a 12% reduction in the risk of dying during a study's follow-up period. They also calculated that people with gait speeds of 1 meter per second or faster lived longer than would be expected given their age or gender. (One meter per second is equivalent to 2.2 miles per hour and just a bit slower than the speed needed to cross the street at most timed traffic lights.)

When the researchers factored in body mass index, blood pressure, prior hospitalization, and several other factors, the relationship between gait speed and longevity didn't change much. In other words, walking speed seemed to be independently associated with life expectancy, not just a marker for other conditions that would affect it.

More number crunching produced interesting correlations between gait speed and five- and 10-year survival rates that make some easy comparisons possible. For example, just 15% of the men ages 75 to 84 with a very slow gait speed of less than 0.4 meters per second (imagine someone shuffling) lived for another 10 years. In contrast, half of those with a speedier gait of 1.2 meters per second or faster lived at least 10 years. Women live longer than men, so the survival rates were longer at both slow and fast speeds for them, but the pattern was the same: faster walkers had much better five- and 10-year survival rates than slower ones.

So does this mean that if you're older and you work on improving your walking speed, you'll live longer? No, you can't draw that kind of a cause-and-effect conclusion from this study, which is based on statistical associations in observational studies. On the other hand, countless other studies have shown associations between physical activity and better health and longer life. For the vast majority of people at any age, regular walking improves health.

The University of Pittsburgh re searchers envision a day when standardized measures of gait speed, along with other information, might be a low-tech way for doctors and other clinicians to assess the overall health and life expectancy of their patients. In fact, you could do it yourself at home. All that's needed is a reliable watch that keeps track of seconds and some tape to mark off four meters in a hallway or large room. A slow gait could trigger action to improve modifiable risk factors or, in a very old person, to avoid certain interventions — say, certain types of surgery — because life expectancy is too short. Clinicians would also be a position to give their fast-walking patients the good news about their health and life expectancy prospects.