There is increasing evidence that sitting for long periods is bad for health, regardless of whether a person exercises. Now, a new study finds sedentary behavior may worsen the health of individuals who already have heart disease, even if they are active.

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Researchers found prolonged sitting was linked to higher BMI and lower cardiorespiratory fitness in patients with heart disease.

The research - led by Dr. Stephanie Prince of the University of Ottawa Heart Institute in Canada - was recently published in the European Journal of Cardiovascular Prevention.

Studies show that we spend around 7.7 hours a day sitting down, which can have severe consequences for health, including increased risk of type 2 diabetes, obesity and heart disease. Recent studies have shown sedentary behavior may even increase the risk of anxiety and non-alcoholic fatty liver disease.

What is more, some studies have suggested that regular exercise may not counteract the negative health effects associated with sedentary behavior.

But what about individuals who already have certain health conditions? Does prolonged sitting worsen their health? And if so, does exercise offset such effects? This is what Dr. Prince and colleagues wanted to find out.

Exercise does not reduce sitting risks for heart disease patients

For their study, the team enrolled 278 patients with coronary heart disease (CHD) - the most common form of heart disease and a leading cause of death for men and women in the US.

All participants had completed a cardiac rehabilitation program, which showed them how to increase physical activity levels.

Fast facts about CHD
  • CHD is caused by a build-up of plaque in the coronary arteries, which prevents oxygen-rich blood from reaching the heart muscle
  • CHD kills around 370,000 Americans every year
  • High blood pressure, high cholesterol, overweight and obesity and diabetes are key risk factors for CHD.

Learn more about CHD

For 9 days, participants wore an activity monitor during waking hours, allowing the researchers to assess how long each subject spent sitting down and how long they spent engaging in light, moderate or vigorous exercise.

Additionally, the researchers assessed participants' body mass index (BMI) and cardiorespiratory fitness - the ability to engage in moderate- or high-intensity exercise for long periods - among other markers of health.

The team found that the participants were sedentary for an average of 8 hours daily, which they say was surprising given that they completed a program showing them how to get more exercise. "We assumed they would be less sedentary but they spent the majority of their day sitting," notes Dr. Prince.

On average, men spent 1 hour more sitting each day than women, which the researchers say is because women engaged in more light activity, such as housework and running errands.

Importantly, the researchers found that subjects who spent more time sitting had higher BMI and lower cardiorespiratory fitness - determined by maximal oxygen consumption, or VO2 peak.

What is more, these findings remained regardless of participants' age, gender or how much time they spent exercising. "In other words, people who sat for longer periods were heavier and less fit regardless of how much they exercised," says Dr. Prince.

The team says their findings emphasize the importance of reducing the amount of time we spend sitting down. Dr. Prince says:

"Limiting the amount of time we spend sitting may be as important as the amount we exercise. Sitting, watching TV, working at a computer and driving in a car are all sedentary behaviors and we need to take breaks from them."

Dr. Prince suggests that information on how to reduce sedentary behavior may benefit heart disease patients taking part in cardiac rehabilitation programs.

Contrary to this and many other studies, research reported by Medical News Today last month suggested that regular exercise can offset the health risks associated with prolonged sitting.