Sitting for long hours increases risk of heart attack in spite of exercise

Sitting for many hours per day is associated with increased coronary artery calcification, that can increase the risk of a heart attack, says a new study. Exercise does not majorly counteract the health effects of a sedentary lifestyle on coronary calcium build up.

In fact, too much sitting might have a greater impact than exercise on this aspect of cardiac health.

Analysing heart scans and physical activity records of more than 2,000 adults in Dallas, the researchers found each hour of sedentary time per day on average was associated with a 14% increase in coronary artery calcification burden.

The association was independent of exercise activity and other traditional heart disease risk factors.

"It's clear that exercise is important to reduce your cardiovascular risk and improve your fitness level," said Jacquelyn Kulinski, MD, assistant professor of cardiovascular medicine at the Medical College of Wisconsin and the study's lead author.

"But this study suggests 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."

Reducing the amount of time you sit by even an hour or two a day could have a significant and positive impact on your future cardiovascular health.

The research follows recent studies linking excess sitting with an increased risk for cardiovascular disease, diabetes, cancer and early death, advising people at work to stand up or move for one to three minutes every half hour.

While those who do not exercise at all are at higher risk, it concluded that it was not good enough to exercise for 30 minutes a day and be sedentary for 23 and half hours.

The present study links sitting and sedentary behaviour with an early marker for heart disease risk.

Future studies need to investigate possible chances of reversing the damage by changing lifestyle habits.

Coronary artery calcification indicates the amount of calcium contained in plaques within the heart's arteries. Coronary artery disease occurs when such plaques accumulate over time, causing the arteries to narrow.

Researchers used a motion-tracking device called an accelerometer to measure how long participants were sedentary and how much they exercised, where earlier studies have relied on surveys.

The results revealed participants sat for a little more than five hours per day on average, with a range of two to 12 hours.

More sedentary participants were older people with higher body mass index, and had diabetes or hypertension.

People with known cardiovascular disease, such as a previous stroke or heart attack, were excluded from the analysis.

"The lesson here is that it's really important to try to move as much as possible in your daily life; for example, take a walk during lunch, pace while talking on the phone, take the stairs instead of the elevator and use a pedometer to track your daily steps," Kulinski said. "And if you do have a very sedentary job, don't go home at night and sit in front of the TV for hours on end."

The study, 'Sedentary Behavior is Associated with Coronary Artery Calcification in the Dallas Heart Study,' is to be presented on 15 March at the American College of Cardiology's 64th Annual Scientific Session in San Diego.