A study published in JACC, the flagship journal of the American College of Cardiology, and presented at the American Heart Association’s Scientific Sessions 2024, indicates that spending more time sitting, reclining, or lying down during the day may increase the risk of cardiovascular disease (CVD) and death. Specifically, the study found that engaging in more than roughly 10 and a half hours of sedentary behaviour per day is significantly associated with an increased risk of future heart failure (HF) and cardiovascular (CV) death, even among individuals who meet the recommended levels of physical activity.
“Our research indicates that reducing sedentary time can lower the risk of cardiovascular issues. We found that spending 10.6 hours a day in sedentary activities may be a critical threshold associated with an increased risk of heart failure and cardiovascular mortality,” said Dr. Shaan Khurshid, a cardiologist at Massachusetts General Hospital and co-senior author of the study. “Excessive sitting or lying down can be detrimental to heart health, even for otherwise active individuals.”
Insufficient exercise is a well-recognized risk factor for cardiovascular disease (CVD). Current guidelines recommend 150 minutes of moderate-to-vigorous physical activity each week to support heart health. However, experts note that exercise constitutes only a small part of our daily activity. Additionally, the guidelines do not address sedentary behaviour, which is a much larger portion of our daily routines. This is noteworthy because evidence shows that sedentary behaviour is directly linked to an increased risk of CVD.
This study analyzed the levels of sedentary time linked to the greatest cardiovascular disease (CVD) risk and investigated how sedentary behavior and physical activity combined influence the likelihood of atrial fibrillation (AF), heart failure (HF), myocardial infarction (MI), and cardiovascular mortality.
The average age of the 89,530 study participants in the UK biobank was 62, and 56.4% were women. Participants submitted data from a wrist-worn triaxial accelerometer that captured movement over seven days. The average sedentary time per day was 9.4 hours.
After an average follow-up of eight years, 3,638 individuals (4.9%) developed incident AF, 1,854 (2.1%) developed incident HF, 1,610 (1.84%) developed indecent MI and 846 (0.94%) died of CV causes, respectively.
The effects of sedentary time varied by outcome. For AF and MI, the risk increased steadily over time without major shifts. For HF and CV mortality, the increase in risk was minimal until sedentary time exceeded about 10.6 hours a day, at which point risk rose significantly, showing a “threshold” effect for the behaviour.
For study participants who met the recommended 150 minutes of moderate-to-vigorous physical activity or more, the effects of sedentary behaviour on AF and MI risks were substantially reduced, but effects on the higher risk of HF and CV mortality remained prominent.
“Future guidelines and public health efforts should stress the importance of cutting down on sedentary time,” Khurshid said. “Avoiding more than 10.6 hours per day may be a realistic minimal target for better heart health.”
In an accompanying editorial comment, Charles Eaton, MD, MS, Director of the Brown University Department of Family Medicine, said the use of wearable accelerometers has shown that self-reporting significantly overestimates exercise and underestimates sedentary behavior.
Eaton said that replacing just 30 minutes of excessive sitting time each day with any type of physical activity can lower heart health risks. Adding moderate-to-vigorous activity cut the risk of HF by 15% and CV mortality by 10%, and even light activity reduced HF risk by 6% and CV mortality by 9%.