Sedentary Behavior Even in Active Individuals Poses CV Health Risks

Even those who meet recommended levels of exercise should be mindful of their time spent sitting, reclining, or lying down because time spent in these positions during the day may increase risk for cardiovascular (CV) disease, according to a study published in JACC and presented at the American Heart Association Scientific Sessions 2024.

The findings suggest that around 10.5 hours of sedentary behavior per day was significantly linked with future heart failure and CV death, even among those who meet recommended levels of exercise, which is 150 minutes or more of moderate to vigorous physical activity per week.

The research group, led by Shaan Khurshid, MD, MPH, examined the amount of sedentary time that had the strongest link to CV disease risk as well as how sedentary behavior and physical activity together could affect the chances of atrial fibrillation (HF), heart failure, myocardial infarction (MI), and CV mortality.

Data were collected from 89,530 participants of the UK Biobank with an average age of 62 years; 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
• 846 (0.94%) died of CV causes

Participants who met the recommended 150 minutes or more of moderate to vigorous physical activity had a substantially reduced risk for AF or MI due to sedentary behavior, but effects on higher risk for HF and CV mortality remained prominent.

In multivariable models, using the second quartile (8.2-9.4 h/d) as a referent, sedentary time in the top quartile (>10.6 h/d) was associated with greater risks for HF (hazard ratio [HR], 1.45; 95% CI, 1.28-1.65) and CV mortality (HR, 1.62; 95% CI, 1.34-1.96), with an inflection of risk at 10.6 h/d.

Higher sedentary time was also associated with greater risks for incident AF (HR, 1.11; 95% CI, 1.01-1.21) and MI (HR, 1.15; 95% CI, 1.00-1.32), with an approximately linear relation.

Among individuals with more than 10.6 hours per day of sedentary time, reallocating sedentary behavior to other activities substantially reduced the excess CV risk conferred by sedentary behavior. For example, a 30-minute decrease in sedentary time for HF (HR, 0.93; 95% CI, 0.90-0.96), even among individuals meeting guideline-recommended exercise levels (HR, 0.93; 95% CI, 0.87-0.99) reduced excess CV risk.

“Sedentary behavior is broadly associated with future adverse CV outcomes, with particularly prominent effects on HF and CV mortality, where risk inflected at approximately 10.6 h/d. Although guideline-adherent MVPA partially mitigates excess risk, optimizing sedentary behavior appears to be important even among physically active individuals,” the researchers concluded.