In November 2021 a notable event in the science of heart disease passed unnoticed by the popular press. That, in itself, is not noteworthy, but then two months later the New York Times health columnist Jane Brody called our attention to the publication of a promising article in the November issue of the Journal of the American Medical Association that could change the way your heart disease is treated, some day. This is a tale of promise and inertia, or the resistance to change in the practice of medicine.
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The question that drove this study is rooted in the conventional wisdom that stress can kill you. Periodically, scientific reports add to this wisdom, or challenge it. For example, in 2008 the New England Journal of Medicine published an article by a group from Germany who had studied the pattern of cardiovascular events in the Munich area during the 2006 World Cup. They assessed 4279 cardiovascular events and reported that on days when the German team played, the incidence of cardiac emergencies around Munich was 2.66 times higher than on the other days (3.26 for men, 1.82 for women). Nearly half of those with cardiovascular events had known heart disease. You might guess from this report that German men with heart disease might have learned over the last 15 years to be more cautious about their lethal habits of watching their national team. Sorry, not yet. But if you have heart disease, one question you’re likely to ask your cardiologist is, “What kinds of stress could kill me?” Good question, but your cardiologist can’t answer it, not yet.
In fact, there have been at least 25 studies and two good reviews showing that some form of mental stress causes some amount of ischemia in the hearts of people with heart disease, raising their risks for further heart attacks and early death. Is that enough to convince cardiologists to evaluate mental stress as well as physical stress tolerance when assessing the severity of heart disease risks? Not yet. All of these studies have major limitations.
And there’s a lesson here about the current resistance to change in the practice of medicine. To effectively change the way we treat a complex chronic illness like coronary heart disease, the standard procedure requires at least four steps:
1) Identify and measure a new factor that might change the course of the illness
2) Prove that this factor consistently changes the course of the illness in significant ways for a significant number of people
3) Show that modifying that factor with a treatment improves the course of the illness
4) Show that this treatment can be delivered in a cost-effective way to those who most need it
Any scientific standard less rigorous than this offers an open invitation to sham treatments, of which there are many vying to be accepted in the marketplace of medicine.
So the publication in November 2021 of the article by Viola Vaccarino and her colleagues at Emory University moves the field from step 1) to step 2) by presenting the definitive study of a “new factor,” mental stress-induced ischemia. The authors compared the relative importance of mental stress-induced ischemia to the traditional exercise-induced ischemia for the prediction of the progression of coronary heart disease over six years. This study improves on the limitations of previous studies. It’s the largest (N= 918) and most diverse study of its kind; it used the most advanced measures of stress and ischemia; and it’s the first to compare the traditional physical stress test to the newer mental stress test for predictive power in a prospective design.
They found that 16% of the sample had mental stressed induced ischemia, 31% had physical (“conventional”) stress-induced ischemia, and 10% had both. The findings, as summarized in Figure 3 of the article, are hard to argue with. Figures like this are a scientist’s dream:
The risk or hazard ratio (HR) of a heart attack or death over six years is highest (3.8) for those who had ischemia during both the mental and the physical stress tests at the start of the study. And the risk for those who only had ischemia during the mental stress test (2.0) was significantly higher than the risk for those with no ischemia. Those who only had ischemia during the physical stress test (1.4) were not significantly more likely to have a heart attack or die than those with no ischemia.
This study makes a compelling argument that during the past fifty years of doing stress tests for heart disease, we may have been paying attention to the wrong kind of stress. There’s another kind of stress we can’t afford to ignore because it’s a much better predictor of bad outcomes. And this study makes this argument by consistently showing that mental stress-induced ischemia changes the course of heart disease in a significant way for a significant number of people.
Now we need to know more about who these people are. For example, if you have heart disease, you don’t really care whether a public speaking challenge in Dr Vaccarino’s lab raises the ST segments on your EKG. You care whether arguing with your spouse or watching your favorite team deprives your heart of the oxygen it needs. And you care what’s going on in your heart on that day when you hear you’ve lost your job, you tested positive for COVID, your daughter smashed your windshield to steal your phone for her drug deal, and your fridge dies. That’s when you need to know how your heart is handling stress. Currently, neither your primary care clinician nor your cardiologist can tell you if you’re one of those 16% whose heart struggles under mental stress. We need better measures of daily stress, both physical and mental, before we change how we manage heart disease. Devices that do that measuring are coming down the pipeline.
As much as any single study can do, this one not only opens the door to further studies, it demands that the next round of studies answer the questions left for steps 3) and 4) about the effectiveness and feasibility of treatment for mental stress.We need to know what, if anything, can buffer your heart from toxic stress, not just for one day, but over and over.Treatment trials will surely come too. And when that day comes, when the inertia of medicine yields to a change of heart about the role of the mind in coronary heart disease, this study should be remembered as one that helped modern medicine turn that corner and see how mental stress drives the course of this disease.