Study: Stress at Work Linked to Heart Disease
Researchers said they have found strong evidence of how work stress is linked to the biological mechanisms involved in the onset of heart disease.
According to the researchers, the study is the first large-scale effort to look at the cardiovascular mechanisms of work stress in the population. The research, published in the European Heart Journal on Jan. 23, is part of the long-running Whitehall II study, which has been following 10,308 London-based civil servants since 1985, and which is led by Sir Michael Marmot, professor of epidemiology and public health at University College London (UCL), UK.
Dr. Tarani Chandola, a senior lecturer in UCL's Department of Epidemiology and Public Health, the first author of this EHJ study, said: "Stress at work is associated with an increased risk of coronary heart disease but the mechanisms underlying this association have remained unclear until now.
Chandola said they study addressed three questions:
- Is the accumulation of work stress associated with higher risks of incident CHD and risk factors?
- Is this association stronger among working-age populations?
- Does work stress affect CHD directly through neuroendocrine mechanisms, or indirectly through behavioural risk factors for CHD, or both?
The researchers collected evidence on the incidence of CHD, deaths from CHD, non-fatal myocardial infarctions, angina, heart rate variability, morning rises in the levels of the "stress" hormone cortisol, the metabolic syndrome and behavioural risk factors such as diet, exercise, smoking and drinking.
The researchers said that during 12 years of follow-up, they found that chronic work stress was associated with CHD and this association was stronger among both men and women aged under 50; their risk of CHD was an average of 68 percent more than for people who reported no stress at work. Among people of retirement age (and therefore less likely to be exposed to work stress), the effect on CHD was less strong.
Chandola said the most important new finding was the evidence linking work stress with the biological mechanisms underlying CHD. The autonomic nervous system (ANS) is the part of the nervous system that regulates involuntary actions, such as the action of the heart, and it has a central role in the neuroendocrine stress responses. The signals that are sent to the heart by the vagus nerve, telling it how to work and controlling the variability of the heart rate, are mediated by the ANS.
The researchers found that workers who suffered from greater stress were more likely to have lowered heart rate variability. They also found that the hypothalamic-pituitary-adrenal axis (HPA) -- a major part of the neuroendocrine system -- was disturbed by greater stress, and this was shown by the fact that stressed workers had higher than normal morning levels of cortisol. These results were independent of the workers' health behaviors.
The researchers also found work stress was associated with poor health behaviors that could lead indirectly to CHD. Work stress is associated with a poorer diet in terms of eating less fruit and vegetables, and less exercise. In this study, around 32 percent of the effect of work stress on CHD could be explained by its effect on health behaviors and the metabolic syndrome, the researchers said.