Even with breaks for exercise, lengthy sitting linked to heart disease

A gamer in 2007
Even when sitting is punctuated by moderate-to-intense workouts, those who spend long hours in a chair or on the couch have higher levels of coronary artery calcium -- a key risk for heart attack -- says a new study.
(Ricardo DeAratanha / Los Angeles Times)

Bad news for the desk-bound office worker, the long-haul road warrior and the couch surfer: even a heart-pumping regimen at the gym, apparently, won’t undo the harm done by sitting, a new study finds.

Irrespective of hours spent in moderate-to-intensive physical activity, says the new research, those who do the most sitting have the highest levels of coronary artery calcification in the arteries feeding oxygenated blood to their hearts.

Coronary artery calcification leads to the formation of sticky plaques inside our arteries, causing narrowing and breaking off to cause heart attacks. A study to be presented at an upcoming meeting of the American College of Cardiology said that, in 2,031 subjects participating in the Dallas Heart Study, levels of this early biomarker for heart disease tracked neatly with the hours of daily sitting measured by an accelerometer.

That neat parallel was not at all perturbed when the researchers considered subjects’ exercise patterns. For each daily hour of sedentary time, average coronary artery calcification levels increased by 14%.


On average, participants spent 5.1 hours sitting daily. The average of time spent in daily exercise was only six minutes, said Dr. Jacquelyn Kulinski a professor of cardiovascular medicine at the Medical University of Wisconsin, and the study’s lead author.

Recent studies have linked excess sitting with higher rates of diabetes, cardiovascular disease, cancer and early death. But the latest research marks the first to show that, by one measure of health at least, punctuating sedentary behavior with exercise does not undo the harm of sitting for lengthy periods.

“It’s clear that exercising is important to reduce your cardiovascular risk and improve your fitness level,” said Kulinski. “But this study would suggest that reducing how much you sit every day may represent a more novel, companion strategy (in addition to exercise) to help reduce your cardiovascular risk.”

Kulinski added that future research should focus on how fewer hours of sitting can improve health.


Watching the nation’s weight as well as your own? Yeah, me too. Follow me on Twitter @LATMelissaHealy and “like” Los Angeles Times Science & Health on Facebook.

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