Daily strides may mean longer life for older women

Older women who get in enough steps each day to walk the equivalent of about two miles - far less than the five-mile goal set by many Americans - might still live longer than their less active counterparts, a US study suggests.

Many people trying to achieve a healthy weight and stay in shape set a daily goal of 10,000 steps, or about five miles, often because they use a fitness tracker with that target, researchers write in JAMA Internal Medicine.

But there isn't solid evidence that this goal is right for everyone, and it's also unclear how much intensity or speed matter when counting the health benefits of every step, the authors note.

For the current study, researchers had almost 17,000 women in their early 70s wear accelerometers for at least four days to track their total daily steps and the intensity of their movements. Overall, participants logged an average of 5,499 daily steps, or roughly 2.5 miles.

During an average follow-up period of 4.3 years, 504 women died. Compared to women who logged no more than 2,718 steps daily, women who achieved at least 4,363 daily steps were 41 per cent less likely to die.

"Even a modest amount of steps is associated with lower mortality," said lead study author Dr. I-Min Lee of Harvard Medical School and Brigham and Women's Hospital in Boston.

"More steps taken per day were associated with even lower mortality rates until about 7,500 steps/day, beyond which no further declines were observed," Lee said by email. "The rate of stepping did not matter in these older women; it was the number of steps that mattered."

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Data from the accelerometers showed that women achieved an average peak 1-minute step intensity of 92 steps per minute, and an average peak 30-minute intensity of 58 steps per minute. A 2.5 mile per hour walking pace is approximately 100 steps per minute.

While intensity did initially seem to be associated with lower mortality risk, this connection disappeared once researchers also accounted for the total number of daily steps women logged. This suggests that step volume, rather than intensity, may be more important for longevity among older women.

At the start of the study, women were 72 years old on average.

While they were wearing accelerometers, the women spent 51 per cent of their time taking no steps at all, and another 46 per cent of the time moving at a pace of no more than 39 steps per minute.

Women spent just 3 per cent of their time moving at a pace of at least 40 steps per minute, a speed that suggests more purposeful effort.

The study wasn't a controlled experiment designed to prove whether or how the number or intensity of daily steps might directly impact the women's risk of death. It also cannot say if healthier women were more likely than less-healthy peers to be active, which could explain some of the association between higher step counts and lower mortality.

One limitation of the study is that researchers only measured women's movements once, at the start of the study period, and it's possible their habits changed over time.

Still, the results are "good news for older adults who may have difficulty walking at faster paces," said Keith Diaz, a researcher at Columbia University Medical Center in New York City who wasn't involved in the study.

"Any walking is better than nothing," Diaz said by email. "With even small amounts of walking, your risk of death will be sharply reduced."

"For those who have difficulty walking, other research shows that any form of aerobic activity provides health benefits," Diaz added. "Swimming, bicycling, arm cranking or any form of activity that is continuous in nature will provide health benefits."