Sitting for Too Long Can be Bad for Your Heart, Even for Active People

According to a study in JACC presented at the American Heart Association Scientific Sessions 2024, spending more time sitting, lying, or in a reclining position during the day may increase the risk of cardiovascular disease and death. More than about 10.5 hours of sedentary behavior per day was significantly associated with future heart failure (HF) and cardiovascular (CV) death even in individuals who met recommended levels of physical activity. “Our findings support reducing sedentary time as a way to lower cardiovascular risk. 10.6 hours per day represents a potentially critical threshold associated with higher heart failure and cardiovascular mortality,” said Shaan Khurshid, MD, MPH, cardiologist at Massachusetts General Hospital and co-senior author of the study.

How Sitting Increases the Risk of Cardiovascular Disease

A sedentary lifestyle is a well-known risk factor for cardiovascular disease (CVD). Current guidelines recommend more than 150 minutes of moderate to vigorous physical activity per week to promote heart health. However, experts say that exercise accounts for only a small portion of total daily activity and the current guidelines do not include specific recommendations on sedentary behavior, which accounts for a much larger portion of daily activity, although there is evidence that it is directly related to CVD risk.

This study examined the duration of sedentary behavior at which the risk of cardiovascular disease is greatest, and how physical inactivity and physical activity together affect the risk of atrial fibrillation (AF), heart failure (HF), myocardial infarction (MI), and cardiovascular mortality. The mean age of the 89,530 UK Biobank participants was 62 years, and 56.4% were women. Participants submitted data from a triaxial wrist-worn accelerometer that recorded movement over seven days. The average sedentary time per day was 9.4 hours. After an average follow-up of eight years, 3,638 people (4.9%) developed atrial fibrillation, 1,854 (2.1%) developed heart failure, 1,610 (1.84%) suffered a non-fatal heart attack and 846 (0.94%) died from cardiovascular causes.

Just 30 minutes of Exercise per Day, Replacing Excessive Sitting, Can Reduce the Risk of Heart Disease

The effects of sedentary time varied by outcome. For atrial fibrillation and heart attack, the risk increased steadily over time, with no major shifts. For heart failure and cardiovascular mortality, the risk increase was minimal until sedentary time exceeded about 10.6 hours per day. From that point on, the risk increased significantly, suggesting a behavioral “threshold” effect.

Among study participants who met the recommended 150 minutes of moderate-to-vigorous physical activity or more, the effects of a sedentary lifestyle on the risk of atrial fibrillation and heart attack were substantially lower, but the effects on the higher risk of heart failure and cardiovascular mortality remained significant. Future guidelines and public health interventions should emphasize the importance of reducing sedentary time, according to the researchers.

In an accompanying editorial, Dr. Charles Eaton, MS, director of the Department of Family Medicine at Brown University, said that the use of wearable accelerometers has shown that self-reported exercise significantly overestimates and sedentary behavior underestimates physical activity. He noted that just 30 minutes of exercise per day replacing excessive sedentary time can lower the risk of heart disease. 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 cardiovascular mortality by 9%.

The study has several limitations, including an inability to get details about where or why people are sitting or lying down for extended periods of time, such as in the workplace, which could have different effects on cardiovascular disease risks. Wrist-worn accelerometers are not perfect at detecting posture and may therefore misclassify periods of standing as periods of sitting. A longer observation period can provide more accurate data on activity habits and patterns.