Sedentary individuals have a significant increase in a marker of subclinical heart disease, according to a recent study. Each additional hour spent seated per day was associated with a 14% increase in the amount of coronary artery calcification seen on CT imaging.

Even for those who exercise vigorously but also spend many hours sitting, prolonged sedentary activity was independently associated with greater CAC. The effect held true even after adjustment for other known cardiac risk factors, according to Dr. Jacquelyn Kulinski of the Medical College of Wisconsin, Milwaukee, and colleagues at Dallas’ University of Texas Southwestern Medical Center. The results were released in advance of their presentation on March 15 at the annual meeting of the American College of Cardiology in San Diego.

Using data from wrist accelerometers in the Dallas Heart Study, a multi-ethnic, population-based sample of adults residing in Dallas, Tex., Dr. Kulinski and colleagues assessed the activity of 2,031 participants without known cardiovascular disease. The median age was 50, about 62% were female, and about half of the participants were black.

The accelerometer, worn on the nondominant hand, captured 7 consecutive days of minute-by-minute activity, and could differentiate between sedentary behavior (sitting or reclining during waking hours), nonexercise activity (such as light movement around the house or a workplace), and more vigorous, purposeful exercise. CAC was assessed via two cardiac CT scans and a standardized scoring system.

Overall, participants had an average 5 hours of sedentary time per day, with a range of 2-12 hours. Higher amounts of sedentary time were associated with being older, having a higher body mass index, and having diabetes or hypertension.

The multivariate analysis included adjustments for patient demographics, clinical characteristics, and the amount to which participants participated in moderate to vigorous physical activity. The researchers found that each additional hour of sedentary time during the day was associated with a statistically significant, 14% increase in CAC. Somewhat surprisingly, Dr. Kulinski noted, there was no association between the amount of moderate to vigorous physical activity and the amount of CAC detected.

Sedentary behavior, sometimes called “sitting disease,” has previously been identified as an independent risk factor for heart disease. These findings, she said, further bolster the concept that “lack of exercise and too much sitting are independent risk factors for CAD and death.”

Dr. Kulinski noted that although fitness is one of the strongest predictors of cardiac health and longevity, there has not been a clear demonstration that increased amounts of exercise are associated with less CAC. This has been true although CAC is an established marker of early formation of the plaque that can lead to coronary artery blockage. The present study suggests that sedentary behaviors, rather than lack of vigorous exercise, may contribute more to the development of CAC than had previously been known.

ACC Vice President Richard Chazal of Lee Memorial Health System, Fort Myers, Fla., remarked in a press briefing before the meeting that this information should be reassuring to patients. “Sometimes just moving around some, even short of a vigorous exercise program, is important,” said Dr. Chazal. “Regular exercise further reduces risk, and it may do so by a mechanism distinct from coronary artery calcification.”

“On a positive note,” Dr. Kulinski said, “reducing daily sitting time by even 1-2 hours could have a significant and positive impact on future cardiovascular health, and this should really be investigated in future studies.”

Dr. James de Lemos disclosed ties with Amgen, DiaDexus, Novo Nordisk, St. Jude Medical, Abbott Diagnostics, and Siemen’s Diagnostics. Dr. Jarrett Berry reports ties with Nihon and Merck. The remaining authors have no disclosures.


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