SITTING FOR LONG PERIODS IS DANGEROUS EVEN FOR ACTIVE PEOPLE.

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SITTING FOR LONG PERIODS IS DANGEROUS EVEN FOR ACTIVE PEOPLE.





Approximately 10 hours or more of sedentary behavior per day is associated with a heightened risk of heart failure and cardiovascular death, even in those who regularly exercise.



More time spent sitting, reclining, or lying down during the day may increase the risk of cardiovascular disease (CVD) and death, according to a study in JACC, the flagship journal of the American College of Cardiology, and presented at the American Heart Association's Scientific Sessions 2024. More than roughly 10-and-a-half hours of sedentary behavior per day was significantly linked with future heart failure (HF) and cardiovascular (CV) death, even among people meeting recommended levels of exercise.

"Our findings support cutting back on sedentary time to reduce cardiovascular risk, with 10.6 hours a day marking a potentially key threshold tied to higher heart failure and cardiovascular mortality," said Shaan Khurshid, MD, MPH, a cardiologist at the Massachusetts General Hospital and co-senior author of the study. "Too much sitting or lying down can be harmful for heart health, even for those who are active."

Insufficient exercise is a known risk factor for cardiovascular disease (CVD). Current guidelines recommend over 150 minutes of moderate-to-vigorous physical activity per week to promote heart health. However, study experts say exercise is only a tiny fraction of overall daily activity, and the current guidelines don't provide specific guidance on sedentary behavior, which accounts for a much more significant portion of daily activity, despite evidence that it's directly linked with CVD risk.

This study examined the amount of sedentary time at which CVD risk is most significant. It explored how sedentary behavior and physical activity together impact the chances of atrial fibrillation (AF), heart failure (HF), myocardial infarction (MI), and CV 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 significant 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 behavior.

For study participants who met the recommended 150 minutes of moderate-to-vigorous physical activity or more, the effects of sedentary behavior on AF and MI risks were substantially reduced. Still, the effects of 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 replacing 30 minutes of excessive sitting daily with any 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%.

"This study adds to the growing evidence of a strong link between sedentary behavior and cardiovascular health," said Harlan M. Krumholz, MD, SM, Harold H. Hines Jr. Professor at Yale School of Medicine and Editor-in-Chief of JACC. "The findings strongly suggest that we need to get people moving to promote better health."

Several limitations of the study exist, including the need for details on where or why people are sitting or lying down for extended periods, such as at the workplace, which could impact CV risks differently. Accelerometers worn on the wrist are imperfect at detecting posture and, therefore, may misclassify standing time as sedentary time. An extended monitoring period may provide more accurate data on activity habits and patterns. Limitations include the potential for confounders in study results, selection bias, the inability to measure the actual effects of reallocating sedentary time to other activities, and differences between data from wrist-worn accelerometers versus thigh-worn accelerometers.



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