Danger of the desk

July 3 2012 - A small-scale study reported recently that, while men are generally more prone to heart disease, women seem more susceptible to coronary risks from emotional stress. The study from Penn State College of Medicine by Charity L. Sauder, Alison E. Thompson, Terrell Myers, and Chester A. Ray, looked at the effects of mental stress on blood flow through the heart.

They found show that coronary blood flow increases in men subjected to mental stress but does not change in women. In the experimental situation they used, both sexes showed an increase in heart rate and blood pressure. Previous studies showed that men had significantly lower flow during physical stress from exercise showed. This offers an explanation to why women may be more susceptible to adverse cardiac events when they are placed in mentally stressful situations.

How work stress can lead to coronary heart disease

Research from University College, London published in the European Heart Journal in 2008 threw some light on how work stress is linked to the onset of coronary heart disease (CHD) either by directly activating stress pathways controlled by interactions between the nervous system, endocrine glands and their hormones (neuroendocrine mechanisms), or indirectly through the association between stress and unhealthy lifestyles. The research is part of the Whitehall II study, led by Sir Michael Marmot, professor of epidemiology and public health, which has been following 10 308 London-based civil servants since 1985.

Lead author Tarani Chandola, senior lecturer in the department of epidemiology and public health 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. This study addressed three questions:

1. Is the accumulation of work stress associated with higher risks of incident CHD and risk factors?
2. Is this association stronger among working-age populations?
3. Does work stress affect CHD directly through neuroendocrine mechanisms, or indirectly through behavioural risk factors for CHD, or both."

Researchers analysed data on the incidence of and mortality from CHD, non-fatal myocardial infarctions, angina, heart rate variability, morning rises in levels of the "stress" hormone cortisol, the metabolic syndrome (a combination of high waist measurement, high fasting glucose, high triglycerides, high HDL cholesterol and hypertension associated with increased risk of heart disease and diabetes) and behavioural risk factors (such as diet, exercise, smoking and drinking).

Tarani Chandola commented:

"During 12 years of follow-up, we 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 per cent 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."

Researchers explained that the most significant new findings linked work stress with biological mechanisms underlying CHD. The autonomic nervous system (ANS) that regulates involuntary actions, such as that of the heart via the vagus nerve, has a central role in neuroendocrine stress responses. The study found that workers who suffered from greater stress were more likely to have lowered heart rate variability and poor vagal tone. They also found that another major part of the neuroendocrine system - the hypothalamic-pituitary-adrenal axis - was affected, demonstrated by raised morning levels of cortisol in stressed workers. These results held true after adjusting for behavioural risk factors.

Tarani Chandola said

"Adjusting for health behaviours did not change the association between work stress and low heart rate variability, suggesting a direct effect on the ANS and neuroendocrine function, rather than indirect effects through health behaviours. The effect on the ANS and neuroendocrine function in turn affects the signals to the heart, leading to cardiac instability."

Researchers also found an association between work stress and poor health behaviours that could lead indirectly to CHD.

Tarani Chandola concluded:

"There have been relatively few studies that have found an association between work stress and unhealthy behaviours. Work stress is associated with a poorer diet in terms of eating less fruit and vegetables, and less exercise. It has also been linked to problem drinking, although not in this study. In this study, around 32 per cent of the effect of work stress on CHD could be explained by its effect on health behaviours and the metabolic syndrome."

"This study demonstrates that cumulative stress at work can lead to CHD through direct activation of neuroendocrine stress pathways and indirectly through unhealthy behaviours."

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