Walking associated with reduced mortality risk

"Get up and move."

That's the take-home message from a new study from Ezra Fishman, a doctoral candidate in demography at the University of Pennsylvania, and colleagues from Johns Hopkins University, the National Cancer Institute, the National Institute on Aging and others.

Even for people who already exercised, swapping out just a few minutes of sedentary time with some sort of movement was associated with reduced mortality, according to the research, published in the journal Medicine & Science in Sports & Exercise.

Fishman, part of Penn's Population Studies Center, and the other researchers looked at data from approximately 3,000 people aged 50 to 79 who participated in the National Health and Nutrition Examination Survey conducted by the Centers for Disease Control and Prevention. For the study, subjects wore ultra-sensitive activity trackers, called accelerometers, for seven days, generating data compiled by the CDC. For these same people, the agency then tracked mortality for the next eight years.

The results were striking. The least active people were five times more likely to die during that period than the most active people and three times more likely than those in the middle range for activity.

"When we compare people who exercise the same amount, those who sit less and move around more tend to live longer," said Fishman, the lead author on the paper. "The folks who were walking around, washing the dishes, sweeping the floor tended to live longer than the people who were sitting at a desk."

Previous activity-tracking studies have drawn similar conclusions. But, according to Fishman, such studies usually ask participants to monitor their own exercise frequency and quantity, numbers they notoriously over-report. Also, the trackers used for NHANES have a higher level of precision than what's typically employed.

"Because the device captures the intensity of activity so frequently, every minute, we can actually make a distinction between people who spent two hours a day doing those activities versus people who spent an hour and a half," he said.

To account for chronic conditions or illness influencing mortality rates, Fishman and colleagues statistically controlled for factors like diagnosed medical conditions, smoking, age and gender. They also completed a secondary examination from which they entirely excluded participants with chronic conditions. Their analysis didn't extend to anyone younger than age 50 because not enough of that subset met the study requirements.

Though the scientists didn't discover any magic threshold for the amount a person needs to move to improve mortality, they did learn that even adding just 10 minutes per day of light activity could make a difference. Replacing 30 minutes of sedentary time with light or moderate-to-vigorous physical activity produced even better results.

"You didn't have to even get a good sweat to experience the reduced likelihood of mortality," Fishman said. "Activity doesn't have to be especially vigorous to be beneficial. That's the public health message."

In an ideal world, Fishman said the research would continue with an experiment that randomly assigned people to two groups -- one that received an incentive to increase physical activity, one that didn't -- to establish conclusively that replacing sedentary behavior with light exercise can reduce mortality risk. He said he would also like to see public health officials get more creative about ways to encourage people to move more. Until these happen, however, it's up to individuals to substitute movement for sitting still.

"When it comes to physical activity," Fishman said, "more is better than less, and anything is better than nothing."