We have previously discussed the relationship between stress and heart disease. Now a new study, published in Circulation, reports that men working in jobs in which they have little control over their daily tasks had a reduced variability in their heart rates - and heart rate variability is associated with an increased risk of coronary artery disease.
It has long been known that men with low-paying jobs and little education have a higher risk of heart disease than other men. Much of this increased risk has been attributed to relatively poor eating habits and a greater likelihood of smoking often seen in such individuals. But now it appears that job-related stress also may play a role.
Investigators from England analyzed data from the Whitehall II study, a study that enrolled over 2000 men between the ages of 45 and 68 who worked in three different levels of the British civil service - senior, middle, and low grade civil servants. These workers completed questionnaires related to their level of control over their jobs, education level, smoking history, eating patterns and alcohol use. They also had ECG testing to measure their heart rate variability.
The researchers found that the heart rate variability was significantly lower in low-level workers, and this reduced heart rate variability was related to the workers' lack of control over daily tasks in their jobs.
DrRich Comments:
This study doesn't really prove anything except that crappy jobs stink. However, it strongly suggests that a lack of a sense of control over one's life is an important source of stress, and that the kind of stress it produces is associated with increased cardiac risk.
Normally, a person's heart rate varies a lot over the course of a day. At rest, the sympathetic nervous system (i.e. adrenaline) relaxes, and the heart rate slows. During periods of of exercise or emotional stress, the sympathetic nervous system kicks in, and the heart rate increases. During chronic stress, the sympathetic tone can become chronically elevated, and the heart rate becomes somewhat higher at rest, and its daily variability is reduced. Thus, a decrease in heart rate variability usually reflects chronically elevated tone within the sympathetic nervous system. Such elevated sympathetic tone can change the characteristics of blood vessels, elevate blood pressure, and produce metabolic abnormalities that make heart disease more likely.
So, this new study suggests a mechanism by which chronic work stress - the kind of stress caused by having little or no control over job tasks - can increase the risk of heart disease. Whether this mechanism is more important than some of the more obvious ones - the overeating, chain smoking, and alcohol consumption also produced by chronic job stress - remains to be seen.
