Fitting in a workout after a long day at a desk may not sufficiently counteract the harmful effects of sedentary behavior on heart health, according to a new study from Mass General Brigham.
The study, published on Nov. 15 in the Journal of the American College of Cardiology, found that excessive sedentary behavior, which researchers defined as waking activity with low energy expenditure while an individual is sitting, reclining, or lying down, is linked to an increased risk of heart disease, particularly heart failure and death from cardiovascular causes.
However, these risks can be significantly reduced by substituting sedentary time for other activities, according to the researchers, who recently presented their findings at the American Heart Association’s Scientific Sessions 2024 in Chicago.
Activity Levels Also Associated With Sleep Levels
“Many of us spend the majority of our waking day sitting, and while there’s a lot of research supporting the importance of physical activity, we knew relatively little about the potential consequences of sitting too much beyond a vague awareness that it might be harmful,” lead study author Dr. Ezimamaka Ajufo, a cardiology fellow at Brigham and Women’s Hospital, said in a statement.
For the study, Ajufo and her team analyzed one week of activity-tracker data from 89,530 people with an average age of 62 who were participating members of the UK Biobank prospective cohort. All participants wore a triaxial accelerometer, a device that measures acceleration from three axes, on their wrists for more than seven days to measure their movement.
The researchers examined the relationship between daily sitting time and future risk of four common cardiovascular diseases: atrial fibrillation, heart attack, heart failure, and cardiovascular death. They classified sedentary behavior using a machine learning algorithm.
Researchers documented participants’ time spent sleeping and in sedentary behavior, and their physical activity levels. Participants were also split into the following four groups based on levels of inactivity:
- More than 10.6 sedentary hours per day
- 9.4 to 10.6 sedentary hours per day
- 8.2 to 9.4 sedentary hours per day
- Less than 8.2 sedentary hours per day
Those spending the least time sitting not only showed the most active time but also slept the most. Similarly, participants who spent the most time sitting, besides being the least active, slept the least.
5 Percent Developed Atrial Fibrillation
After follow-up over an average of eight years, about 5 percent of study participants developed atrial fibrillation, about 2 percent developed heart failure, nearly 2 percent experienced a heart attack, and roughly 1 percent died from cardiovascular-related causes.
“Sedentary risk remained even in people who were physically active, which is important because many of us sit a lot and think that if we can get out at the end of the day and do some exercise we can counterbalance it. However, we found it to be more complex than that,” Ajufo wrote.
The researchers’ analysis found that sedentary behavior was associated with a higher risk of all four types of heart disease, with a 40 percent to 60 percent greater risk of heart failure and cardiovascular death observed when sedentary behavior exceeded 10.6 hours a day (excluding hours spent sleeping).
The findings add to previous research linking sitting to disease risk, regardless of activity levels. A large review and meta-analysis of studies published in 2015 found that even after adjusting for physical activity, sitting for long periods was associated with worse health outcomes, including heart disease, Type 2 diabetes, and cancer.
Adverse Effects Persisted Despite Exercise
The latest Physical Activity Guidelines for Americans recommend adults perform at least 75 to 150 minutes of vigorous aerobic activity, or 150 to 300 minutes of moderately intense aerobic activity, every week, along with two days of strengthening exercises.
Notably, many adverse effects persisted even among those who met the recommended physical activity levels.
“Our data supports the idea that it is always better to sit less and move more to reduce heart disease risk, and that avoiding excessive sitting is especially important for lowering risk of heart failure and cardiovascular death,” co-senior study author and electrophysiologist Dr. Shaan Khurshid said in the statement.
The authors plan to expand their research to study how sedentary behavior relates to other diseases over more extended periods.
The research team hopes its findings will inform public health guidelines. The researchers also expressed interest in prospective studies investigating the effects of interventions designed to reduce sedentary behavior and their impact on cardiovascular health.
“Exercise is critical, but avoiding excessive sitting appears separately important,” co-senior author and cardiologist Dr. Patrick Ellinor said in the statement. “Our hope is that this work can empower patients and providers by offering another way to leverage movement behaviors to improve cardiovascular health.”