Taking an extra 4,000 steps a day might reduce our risk of dying prematurely, even if those steps are not T swift, according to a large-scale new study of moving and mortality. At a time when so many of us are confined to home and worried about whether we are being active enough, the study is especially inspiring in that the added steps do not have to come from running or other vigorous exercise. It finds that for every additional 4,000 steps someone takes in a day, even if it's just ambling around the block or across the room, his or her risk of dying early from heart disease, cancer or any other cause drops by 50 per cent or more.

Right now, shelter-at-home restrictions in response to the coronavirus pandemic cover more than three out of every four Americans and millions more worldwide. In this situation, questions about how much and how best to exercise or move about for our health and well-being are pressing.

Typically, the built-in apps on our phones and activity monitors or watches prompt us to accumulate at least 10,000 steps a day. But there are no reliable studies supporting the 10,000step target. Some recent evidence suggests that the number sprang from a 1960s Japanese publicity campaign promoting pedometers with a name that translates as '10,000 steps'.

More recently, studies aiming to pin down the links between step counts and longevity have tended to be small, based on people's memories of their activities or focussed on specific groups of people, such as older women, Caucasians or those with diabetes and other health problems. Because of these limitations, the issue of how many steps are desirable and sufficient for most people remains open, whatever your phone may tell you.

So, for the new study, which was published in March in JAMA, researchers from the National Institutes of Health and the Centers for Disease Control and Prevention decided to look at health and activity data from a large cross-section of Americans.

To accomplish this, they turned to records from the massive National Health and Nutrition Examination Survey, which includes responses from tens of thousands of Americans about their lives and health. Many of these participants also wore activity monitors for a week or so, which objectively tracked their movements.

The researchers pulled data for almost 5,000 men and women who had worn a monitor. All were middle-aged or older and included Caucasian, African American and Hispanic participants from a swath of socio-economic backgrounds.

'We wanted a representative sampling of American adults,' says Charles Matthews, a senior investigator in the National Cancer Institute's Division of Cancer Epidemiology and Genetics and senior author of this particular study.

The scientists noted how many daily steps the men and women averaged, as well as how many steps per minute they accumulated. Both measures are telling. Total step counts reveal how much people are moving, in any fashion, while steps per minute indicate those movements' intensity. Running results in far more steps per minute than strolling, for instance.

They then grouped people by activity, using 4,000-step increments (since that number allowed the most meaningful comparisons), checked the national death registry for participants who had passed away during the past decade and, finally, compared peoples' movement patterns and mortality.

The results were interesting and somewhat surprising, Matthews says. The researchers had expected both the number and intensity of steps to be linked to longevity, he says. But after controlling for gender, age, smoking, body mass index, diet and multiple other factors, only step counts were linked to mortality risk. Step intensity, interestingly, was not.

More specifically, people who averaged about 8,000 steps a day were about half as likely to have died from heart disease, cancer or any other cause as people accumulating 4,000 steps or fewer daily, while men and women completing at least 12,000 daily steps were 65 per cent less likely to have passed away than those in the 4,000-or-less group.

But the researchers found no significant associations between the speed of people's steps and mortality. 'We didn't see any extra benefit from intensity,' Matthews says.