Researchers have figured out why sitting all day is so bad for your health

Kevin Loria

Sitting all day —at the office, in transit to and from work, and on the couch when we get home — is terrible for us. Staying seated for too long is associated with increased risk for diabetes and various cancers, and it can more than double a person's risk for cardiovascular disease.

That's no surprise. But a recently published study sheds light on why exactly sitting is killing us.

It turns out that sitting all day is linked to the buildup of certain proteins called troponins, which heart muscle cells release when they're damaged. Doctors look for a surge of them in people's blood when diagnosing a heart attack.

Specifically, the researchers found that people who sit more than 10 hours a day (not too hard to do for a person who spends 7-9 hours at a desk) had above-normal troponin levels. The numbers weren't high enough to qualify the participants for heart-attack-level damage, but the researchers did refer to the condition as "subclinical cardiac injury."

If those elevated troponin levels persist in a chronic way in people who sit too long every day, that could explain why sedentary people are more likely to die (from cardiovascular problems particularly) than people who spend less time sitting — even if they don't have pre-existing cardiovascular disease.

The researchers made their discovery after analyzing data from a group of participants from the Dallas Heart Study, an ongoing study looking at the heart health of multiethnic residents of Dallas County. They looked at study participants at the beginning and end of a week, measuring troponin levels and tracking physical activity with fitness trackers.

This was the first study investigating a connection between sedentary behavior and troponin levels. But the results don't definitively show that sitting causes this chronic heart damage — just that people who sit more have more signs of heart damage. It's likely there's a strong connection there, though.

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The role of exercise

"The other side of the coin is what you are not doing while you are sitting," Dr. James de Lemos, the senior author of the study, told the New York Times.

If you're not sitting, you're more likely to be moving, which seems to help. But it's unclear whether exercise can fully counteract the negative effects of sitting.

Among study participants who sat for long periods of time but also got some exercise, there seemed to be some attenuating effect. That indicates that exercise helps — perhaps because it improves heart health — but those participants were still more likely to have unhealthy troponin levels than people who sat less.

Other research has shown that people who spend a good amount of time engaged in moderate to vigorous physical activity tend to have lower and therefore healthier troponin levels.

The key might be getting enough exercise to cut down on sitting time. In one major study published last year in the Lancet, researchers said that people who sat for more than eight hours a day but got a minimum of 60-75 minutes of moderate exercise every day had similar risk of death to people who sat just half as much and got the same amount of exercise.

Other researchers have found that getting up and going for a short walk every hour was enough to significantly reduce the risk of death associated with sitting for long periods of time.

Most people already understand that unhealthy behaviors including eating poorly, abusing drugs and alcohol, and skipping sleep are all associated with heart problems. If sitting is also associated with signs of heart damage, that's yet another reason to spend more time on the move and less time at a desk or on the couch.