Study Shows Sedentary Time Increases Cardiovascular Disease
In This Article
- Many national and international guidelines are specific about the amount of exercise people should get, but they are not clear on healthy amounts of sedentary time
- A new study found that higher levels of sedentary time increased the risk of atrial fibrillation, myocardial infarction, heart failure, and CV mortality
- The increased risk was present even in people who achieved the guideline-recommended 150 minutes of moderate to vigorous physical activity per week
- Risk was significantly increased in people who had more than 10.6 hours of sedentary time per day
New research from Massachusetts General Hospital shows that sedentary behavior increases the risk of cardiovascular (CV) conditions and death — even in people who also get the recommended amount of exercise per week.
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"We know that achieving certain levels of moderate to vigorous exercise is important for health. The guidelines are very specific about how much exercise you should get. But in contrast, people spend many hours a day being sedentary, and we wanted to understand whether exercise can kind of negate the effects of sedentary behavior," says Shaan Khurshid, MD, MPH, a cardiac electrophysiologist at Mass General and senior investigator on the study. "Overall, our findings suggest that avoiding excess sedentary behavior is important for cardiovascular benefit whether or not you're physically active."
National Exercise Guidelines Focus on Physical Activity, not Downtime
Many national and international guidelines specifically recommend 150 minutes of moderate to vigorous exercise every week to lower the risk of CV disease, cancer, and other conditions. However, the guidelines are rather vague when it comes to sedentary behavior. They discourage sedentary behavior and encourage people to minimize it but lack specificity, Dr. Khurshid says.
"They don't mention any specific numbers, any specific recommendations, other than to 'sit less.' And we don't know whether, if you exercise, is it still bad to sit or not?" he says.
How Much Sedentary Time Do Most People Get?
Dr. Khurshid and colleagues followed almost 90,000 people who wore activity trackers on their wrists for one week. They collected data on exercise time and intensity, as well as sedentary time — defined as being at rest with less than or equal to 1.5 metabolic equivalents while also sitting, reclining, or lying down. Standing, even when at rest, did not qualify as sedentary time.
Median sedentary time among the entire sample was 9.4 hours per day, broken into quartiles:
- The top quartile of the sample had an average sedentary time of more than 10.6 hours per day.
- The next quartile ranged from 9.5 to 10.6 hours per day.
- The next quartile ranged from 8.2 to 9.4 hours per day.
- The lowest quartile had less than 8.2 hours of sedentary time per day.
"A total of 10.6 hours per day seems like a lot, but if you think about someone who has a desk job and then watches a little TV at night, that actually adds up pretty quickly," Dr. Khurshid says. "U.S. estimates are an average of 9.5 hours per day, so 10.6 is greater than average, but it does represent many people's behavior."
More Sedentary Time Linked to Cardiovascular Risk, Regardless of Exercise Habits
The researchers also tracked incident atrial fibrillation, myocardial infarction, heart failure, and CV mortality over about eight years to discover any associations between sedentary behavior and such events. The results were published in the Journal of the American College of Cardiology.
Greater sedentary behavior was associated with all four outcomes. There were particularly pronounced effects on heart failure (HF) and CV death — 40% to 60% increases, respectively — with the high levels of sedentary behavior observed in the top quartile. The results persisted even when the researchers adjusted for age and several demographic and lifestyle factors.
Exercise Does not Negate the Drawbacks of Sedentary Time
Notably, associations between sedentary time and heart failure and CV mortality risk persisted even among people who met guideline-recommended exercise levels.
"This result suggests an independent effect of sedentary behavior," notes Dr. Khurshid. "Being active is helpful, but it doesn't fully mitigate the risks associated with excess sedentary behavior. So even if you're physically active, reducing your sedentary behavior is still important."
Furthermore, among individuals who had the highest amounts of sedentary time, changing sedentary behavior to other activities substantially reduced the excess CV risk.
"We looked at people in the high sedentary behavior category and analyzed what would happen to their risk if they changed sedentary behavior into anything else. Certainly, moderate to vigorous activity would be helpful, but even if they just changed it to walking, standing, basically doing anything," Dr. Khurshid says. "We saw reductions in the risk for heart failure and CV death."
Other subanalyses confirmed these findings in people who had certain conditions at baseline, such as obesity or diabetes, as well as people with poor self-reported health versus good self-reported health.
Another analysis examined the effects based on the number of days a week a person exceeded 10.6 hours per day. It confirmed that the greater number of days a person exceeded that threshold, the higher their risk of the four CV conditions.
Working to Incorporate Healthy Behaviors That Work for People
Dr. Khurshid encourages healthcare providers to use this new information to provide more specific information to their patients to enhance current guidance on exercise.
In the meantime, he and his team are exploring additional studies about exercise and disease risk. For example, Dr. Khurshid recently published a paper in Circulation showing that "weekend warriors" have a substantially lower risk of 264 diseases compared with people who are inactive. The study found that concentrating physical activity into longer sessions only one or two days a week is just as beneficial as spreading activity more evenly throughout the week.
Much of this work may help people make small changes or incorporate healthy behaviors more easily.
"Studies being done at Mass General are opening the door to creating and testing interventions that ask people to engage with interventions that may be more effective because they're easier to engage with," Dr. Khurshid says.