The role of stress in the pathogenesis of disease (how diseases start and progress) has long been the subject of medical research.  

Hypertension (elevated blood pressure sustained over time) has been one of the main targets.  There is no dispute that episodic stress can temporarily elevate blood pressure, but researchers have not been able to link stress with actual hypertension.  In other words, stress does not seem to chronically elevate blood pressure to the point of a higher risk for cardiovascular disease such as strokes and heart attacks.

What about cancer?  Again, there is no evidence that stress is implicated in causing cancer.  But there is plenty of research that demonstrates stress can be a major factor in exacerbating established cancer.

So a recent study in the Journal of the American Medical Association caught my attention: “Association of Mental Stress-Induced Myocardial Ischemia With Cardiovascular Events in Patients With Coronary Heart Disease.”  In other words, does mental stress predict increased risk for future adverse cardiac events?

The exercise treadmill test is the tried and true method for assessing the presence of coronary heart disease (i.e., narrowed arteries that compromise the flow of blood to the heart muscle, causing heart attacks).  Monitored subjects exercise on a treadmill, and electrocardiograms and sophisticated imaging techniques can fairly reliably predict the presence or absence of significant cardiac disease.  It is a very useful method for patients with obscure chest symptoms and/or as a means to follow possible recurrences in patients with established coronary heart disease.  This method induces physical stress.

But what about psychological stress?  Although many studies have found a link between psychological stress and the risk of coronary heart disease,  they are far from definitive—they are small, largely anecdotal, and lacking in ethnic, racial, and gender diversity.  

In contrast, researchers in the study cited above looked at almost 1,000 diverse patients with established coronary heart disease.  They induced mental stress (public speaking challenge) and used sensitive techniques to detect the presence of cardiac ischemia (i.e., decreased blood flow to the coronary arteries).  They then used conventional stress testing (i.e. treadmill exercise) to test for the presence of coronary ischemia in the same population.  All patients were followed for an average of five years and were monitored for subsequent cardiac events.

The results showed mental stress-induced ischemia to be a significant predictor of future heart attacks and deaths.  Patients who displayed conventionally induced ischemia on the treadmill test were also at higher risk of future heart attacks and death, but at only about two-thirds of the rate of patients who displayed mental stress-induced abnormalities.* 

The authors of the study, and an accompanying editorialist, were careful not to make any wild claims about the implications of the work.  Is mental stress ischemia modifiable? Is the test for mental stress reproducible in multiple clinical settings? Should patients with coronary artery disease be screened for mental stress ischemia, and, if so, what interventions might be undertaken?  Should we view stress, along with other known cardiac risk factors such as smoking, obesity, diabetes, hypertension, sedentary lifestyle, and elevated cholesterol, etc., as another factor that should be assessed in the stratification of risk for cardiac disease?

This study is a valuable contribution to answering these questions.  But no one knows for sure what the role of psychological stress is in heart disease.  This issue will be an increasingly important research topic, and much needs to be done.

*Patients who had abnormalities with both physical and mental induced stress had the highest risk.

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