15,000 steps a day keep heart healthy

Taking 10,000 steps per day is often suggested as a desirable exercise goal for people who wish to improve their health. But a new study of postal workers in Scotland suggests, that number could be too conservative and that, to best protect our hearts, many of us might want to start moving quite a bit more.

It has been almost 70 years since the publication of the London Transit Workers Study, a famous work in which researchers tracked the heart health of London bus drivers and conductors. They found that the conductors, who walked up and down bus aisles throughout the workday, were substantially less likely to develop or die from heart disease than the drivers, who sat almost constantly while at work.

This study was one of the first to show that being physically active could lower someone’s risk for heart disease.

Since then, countless large-scale studies have substantiated that finding, and at this point, there is little doubt that moving or not moving during the day will affect the health of your heart.

But precisely how much exercise might be needed in order to avoid heart disease has remained much in question. The threshold of 10,000 daily steps, incorporated as a goal into activity monitors, has not been scientifically validated as a way to lessen disease risk.

So for the new study, which was published this month in The International Journal of Obesity, researchers at the University of Warwick in England decided to advance and expand upon the results of the Transit Workers Study by examining another group of employees whose workdays involve mostly walking or sitting. They turned to postal workers in Glasgow.

The Glaswegian mail carriers cover their routes on foot, not by driving, and spend many hours each day walking. But the mail service’s office workers remain seated at their desks mostly during the day.

Researchers began by recruiting 111 of the postal-service workers, both men and women, and most between the ages of 40 and 60. None had a personal history of heart disease. Researchers measured volunteers’ body mass indexes, waist sizes, blood sugar levels and cholesterol profiles, each of which, if above normal, increases the chances of cardiac disease. Then they had each volunteer wear a sophisticated activity tracker for a week, while at work and at home and during the weekend.

Afterward, the researchers determined how many waking hours each day the volunteers had spent seated or on foot. They calculated how many steps each person had taken.

Better on foot
The variations turned out to be considerable. Some of the office workers sat for more than 15 hours each day between work and home, while most of the mail carriers barely sat at all during working hours.

These differences were echoed in the volunteers’ risk factors for heart disease. Those workers who sat for most of each day tended to have much larger waistlines, higher BMIs and worse blood sugar control and cholesterol profiles than those who frequently stood and moved, even after scientists controlled for age, family history, late-night shift work and other factors.

The risks were magnified at the extremes. For every hour beyond five that workers sat each day, the researchers found, they added about two-tenths of a percentage point to their likelihood of developing heart disease, based on their cumulative risk factors.

Meanwhile, almost any amount of standing and walking reduced a worker’s chances of having a large waistline and other risk factors for heart disease. But the greatest benefits came from the most exaggerated amounts of activity. Those mail carriers who walked for more than three hours a day, covering at least 15,000 steps, generally had normal BMIs and metabolic profiles.

Of course, this study provides a limited snapshot of people’s health. The researchers did not follow their volunteers for decades to see who actually developed heart disease. This kind of study also cannot prove that walking or sitting caused the differences in people’s risks factors for heart disease, only that there were associations between activity and risks.

But the findings do imply that there are good reasons to get up from our desk chairs and move, says Dr William Tigbe, a physician at the University of Warwick who led the study. “It takes effort,” he says, but we can accumulate 15,000 steps a day by walking briskly for two hours,” he says.