Get Up, Stand Up! By Gretchen Reynolds.

Most of us almost certainly have heard by now that being seated and unmoving all day is unhealthy. Many past epidemiological studies have noted that the longer people sit on a daily basis, the likelier they are to develop various diseases, including obesity, diabetes and heart disease. They also are at heightened risk for premature death.

This association between sitting and ill health generally remains, the past science shows, whether people exercise or not.

New study required:

But most of these studies have relied on people’s memories of how they spent their time on any given day, and our recall about such matters tends to be notoriously unreliable. The studies also usually have focused on the total number of hours that someone sits each day. Some scientists have begun to wonder whether our patterns of sitting — how long we sit at a stretch and whether, when, and how often we stand up and move — might also have health implications. And they have questioned whether gender, race or weight might alter how sitting affects us.

So for the new study, which was published this week in Annals of Internal Medicine, scientists from Columbia University in New York City and many other institutions turned to an extensive database of existing health information about tens of thousands of Caucasian and African-American men and women 45 or older who were part of a study of stroke risk.

The participants had undergone a battery of health tests and about 8,000 of them also had worn accelerometers for a week to track their daily movements. …

The new findings:

The scientists then found strong statistical correlations between sitting and mortality. The men and women who sat for the most hours every day, according to their accelerometer data, had the highest risk for early death, especially if this sitting often continued for longer than 30 minutes at a stretch. The risk was unaffected by age, race, gender or body mass.

It also was barely lowered if people exercised regularly.

But interestingly, the risk of early death did drop if sitting time was frequently interrupted. People whose time spent sitting usually lasted for less than 30 minutes at a stretch were less likely to have died than those whose sitting was more prolonged, even if the total hours of sitting time were the same. …

The accelerometers could not readily distinguish between sitting and standing, Dr. Diaz says, so the “breaks” in sitting time in this study always involved walking about and not merely standing up.