Even those who exercise regularly may have an increased risk of heart failure and cardiovascular death as a result of sitting for ten or more hours a day. That’s according to research published in the Journal of the American College of Cardiology JACC and presented at the American Heart Association conference.

The researchers studied data from the UK Biobank on nearly 90,000 men and women, with an average age of 62. Participants submitted data from a wrist-worn accelerometer to record their movement over seven days. Average sedentary time per day was 9.4 hours.

After an average follow-up of eight years, the researchers found that more than 10.6 hours of sedentary behavior on the day were significantly associated with future heart failure and cardiovascular death. In contrast, the risk of atrial fibrillation and myocardial infarction increased steadily over time without significant changes.

For study participants who met the recommended exercise levels of 150 minutes of moderate to vigorous physical activity per weekthe effect of sedentary behavior on the risks of atrial fibrillation and myocardial infarction were significantly reduced. However, even in them, the effects on the higher risk of heart failure and mortality remained evident.

The researchers note that replacing just 30 minutes of excessive sedentary time each day with any type of physical activity can reduce heart health risks. In the study, adding moderate to vigorous activity reduced the risk of heart failure by 15% and cardiovascular mortality by 10%, and even light activity made a difference, reducing the risk of heart failure by 6% and mortality by 9%.

The researchers point out several limitations to the study, such as that wrist-worn accelerometers are imperfect at detecting body posture and therefore may misclassify standing time as sedentary time.