In recent years human studies of exercise and life expectancy have pointed to a correlation between time spent sedentary and mortality rate, and this correlation appears to be independent of the level of regular exercise undertaken. Here researchers look to calcification as a possible mechanism to explain this association. Calcification of blood vessels and heart tissue occurs with age, and contributes to the tissue stiffness that leads to hypertension, followed by detrimental remodeling of the heart and vascular system to try to compensate. At the end of that road lies cardiovascular disease and death. It isn't completely clear as to whether calcification will occur to a significant degree even if other forms of cell and tissue damage known to cause vascular aging can be repaired, in other words whether calcification is an entirely secondary process of aging. Given that uncertainty it is probably worth adding it as a target for future regenerative therapies.
Researchers have found that sedentary behavior is associated with increased amounts of calcium deposits in heart arteries, which in turn is associated with a higher risk of heart attack. The researchers had previously shown that excessive sitting is associated with reduced cardiorespiratory fitness and a higher risk of heart disease. The latest research - part of the Dallas Heart Study - points to a likely mechanism by which sitting leads to heart disease. "This is one of the first studies to show that sitting time is associated with early markers of atherosclerosis buildup in the heart. Each additional hour of daily sedentary time is associated with a 12 percent higher likelihood of coronary artery calcification." The researchers concluded that reducing daily "sitting time" by even 1 to 2 hours per day could have a significant and positive impact on future cardiovascular health, and called for additional studies into novel interventions to reduce sedentary behaviors. For the many individuals with a desk job that requires them to sit for large portions of the day, they suggested taking frequent breaks.
In some individuals, cholesterol builds up inside the walls of the arteries supplying blood to the heart in mounds called cholesterol plaques. Over time, calcium accumulates in these plaques. The amount of coronary artery calcium can be measured through CT scanning and directly correlates with the amount of cholesterol plaque, as well as with heart attack risk. In this study, the researchers asked some 2,000 participants in the Dallas Heart Study to wear a device that measured their activity levels for a week. Participants spent an average of 5.1 hours sitting per day and an average of 29 minutes in moderate to vigorous physical activity each day. "We observed a significant association between increased sedentary time and coronary artery calcium. These associations were independent of exercise, traditional cardiovascular disease risk factors such as diabetes and high blood pressure, and socioeconomic factors. This research suggests that increased subclinical atherosclerosis characterized by calcium deposition is one of the mechanisms through which sedentary behavior increases cardiovascular risk and that this risk is distinct from the protective power of exercise."