You may need to be more mindful of the amount of time you spend sitting from now on: experts say being sedentary for too long is bad for your heart health.

The American Heart Association (AHA) released on Monday, Aug. 15, a new science advisory that says too much time spent sitting, laying down or reclining is potentially an independent risk factor for stroke and heart disease.

In fact, regardless of how much exercise you get, prolonged sitting time could negatively affect the condition of your blood vessels and heart, says Deborah Rohm Young, chair of the new advisory.

The report corroborates previous studies that reveal the negative effects of sedentary behavior, including the hardening of arteries which may lead to heart attack.

According to the advisory, too much sedentary behavior is also associated with a higher risk of developing diabetes, increased risk of cardiovascular disease, damaged insulin sensitivity, and an overall greater risk of mortality from any cause.

Sit Less, Move More

Researchers found that adults in the United States spend six to eight hours a day in sedentary behavior. Adults who are aged 60 years old and above spend 8.5 to 9.6 hours in sedentary time.

Young says scientists have yet to uncover many important factors related to sedentary time, because the types of available research only identify trends but do not prove a cause-and-effect relationship.

She says the best advice they can give is to "sit less and move more."

"Be conscious of how much time you're spending sitting," says Young. "Try to move more."

Young and the authors advise that Americans aim for about 30 minutes or so of moderate to vigorous physical activity every day. Doing this will help them achieve the weekly 150-minute moderate exercise recommendation from the AHA.

Instead of exerting all the exercise into one or two days, the goal is more consistent physical activity, Young says.

Still, exercise does not cancel out the effects of sedentary behavior. Even people who are physically active but spend a lot of their time sitting appear to have greater risk for the negative effects.

Aside from sitting, sedentary behavior also includes watching television, using the computer or reading. Young says these "inactive activities" mean that energy expenditure is just less than or equal to 1.5 metabolic equivalents.

Housework and leisurely walking uses about 2.5 metabolic equivalents, while moderate to vigorous exercise requires 3.0.

"When you're at home, try not to sit on the couch the whole time," adds Young.

Details of the study are published in Circulation: Journal of the American Heart Association.

Photo: Per Egevad | Flickr