Why sitting may be bad for heart

Sitting quietly for extended periods of time may be hurting your heart, according to a surprising new study. It finds that the more people sit, the greater the likelihood that they will show signs of injury to their heart muscles.

We all have heard by now that sitting for hours on end is unhealthy, even if we also occasionally exercise. People who sit for more than about nine or 10 hours each day are prone to developing diabetes, heart disease and other problems, and most of these risks remain high, even if we exercise.

Excessive sitting also has been associated with heart failure, a condition in which the heart becomes progressively weaker and unable to pump enough blood to keep the rest of the body well. But how sitting, which seems to demand so little from the heart, could be linked to heart failure has been unclear.

So recently a group of cardiologists began to wonder about troponins.

Troponins are proteins produced by cardiacmuscle cells when they are hurt or dying. A heart attack releases troponins into the bloodstream.

For a new study, published in Circulation, the researchers turned to data from the Dallas Heart Study, a large examination of cardiac health among a group of ethnically diverse men and women, overseen by the University of Texas Southwestern Medical Center.

The researchers pulled data about more than 1,700 of these participants, excluding any who had heart disease or symptoms of heart failure.

They checked the blood samples for troponins and the readouts from their activity trackers to see how much they had moved most days.

Overall, sitting was more strongly associated with unhealthy troponin levels than exercise was with desirable amounts.

Of course, this was an observational study and can show only that sitting is linked to high troponin, not that it causes troponins to rise.

But the effects are probably indirect, says Dr. James de Lemos, a cardiologist and professor at the medical center, who oversaw the new study.

“Sedentary behavior is associated with obesity, insulin resistance and fat deposition in the heart, all of which can lead to injury to heart cells,” he said.