More time spent sitting, reclining or lying down during the day may increase the risk of cardiovascular disease and death, according to a study presented at AHA 2024 and simultaneously published in JACC.

Ezimamaka Ajufo, MD, et al., looked at 89,530 study participants of the UK biobank (average age was 62 years 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.

Results showed that after an average follow-up of eight years, 3,638 individuals (4.9%) developed incident atrial fibrillation (AFib), 1,854 (2.1%) developed incident heart failure (HF), 1,610 (1.84%) developed indecent myocardial infarction (MI) and 846 (0.94%) died of cardiovascular causes, respectively.

The effects of sedentary time varied by outcome. For AFib and MI, the risk increased steadily over time without major shifts. For HF and cardiovascular mortality, 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 behavior.

For study participants who met the recommended 150 minutes of moderate-to-vigorous physical activity or more, the effects of sedentary behavior on AFib and MI risks were substantially reduced, but effects on higher risk of HF and cardiovascular mortality remained prominent.

"Future guidelines and public health efforts should stress the importance of cutting down on sedentary time," said Shaan Khurshid, MD, MPH, co-senior author of the study. "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, said the use of wearable accelerometers has shown that exercise is significantly over-estimated by self-report and sedentary behavior is under-estimated. He explains that replacing just 30 minutes of excessive sitting time each day with any type of physical activity can lower heart health risks.

"This study adds to the growing evidence of a strong link between sedentary behavior and cardiovascular health," adds JACC Editor-in-Chief Harlan M. Krumholz, MD, SM, FACC. "The findings strongly suggest that we need to get people moving to promote better health."