Photo of man sitting while watching television

Sitting for too long is associated with more calcium deposits in the heart arteries, according to a study by cardiologists at UT Southwestern Medical Center in Dallas.

Previous research has shown that excessive sitting can reduce cardio fitness and increase the risk of heart disease and death. The new study now gives researchers an idea about how that happens.

“This is one of the first studies to show that sitting time is associated with early markers of atherosclerosis buildup in the heart,” senior author Amit Khera, M.D., director of the preventive cardiology program at UT Southwestern, said in a news release. “Each additional hour of daily sedentary time is associated with a 12 percent higher likelihood of coronary artery calcification.”

Coronary artery calcium can be measured by a CT scan to detect the amount of atherosclerosis, a disease that hardens arteries and underlies many types of heart disease.

Reducing sitting time by one to two hours each day could improve future cardiovascular health, according to researchers. They suggest frequent breaks for people sitting at desks for most of the day.

“Try a one- to five-minute break every hour. Stand up. Walk up a flight of stairs. All of this helps in a small way. Then get in your strenuous exercise in the evening as well,” Julia Kozlitina, Ph.D., assistant professor of internal medicine and clinical sciences at UT Southwestern, said in a news release.

In the study, 2,000 people wore a device that tracked their daily activity for a week. Each day, they averaged 5.1 hours of sitting and 29 minutes of moderate to vigorous exercise.

“We observed a significant association between increased sedentary time and coronary artery calcium,” Khera said. “These associations were independent of exercise, traditional cardiovascular disease risk factors such as diabetes and high blood pressure, and socioeconomic factors.”

The research appears as a “Letter to the Editor” in the Journal of the American College of Cardiology: Cardiovascular Imaging.