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May 16, 2002
Mr. Chairman and Members of the Committee:
I welcome the opportunity to appear before you on behalf of the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health to address the Subcommittee's interest in the role of stress management in reversing heart disease.
The NHLBI has, for many years, supported a vigorous program of research on behavioral factors that contribute to the development, treatment, and prevention of disease. Results from that research make it clear that several modifiable behavioral and psychosocial factors do play a significant role. The influence of stress should be considered in the context of these other risk factors, which include behaviors such as smoking, physical inactivity, diets high in fat and low in fruits and vegetables, and combinations of these risk factors that lead to overweight and obesity. Cumulatively, clinical research on the effects of interventions to alter these behaviors (i.e., to stop smoking, increase physical activity, improve diet, and reduce body weight) has shown that these lifestyle changes can be expected to reduce cardiovascular risk significantly.
Research has also revealed associations between several psychosocial factors and heart disease. The factors include chronic stress, depression, inadequate social support, anxiety, hostility, and socioeconomic status. Each has been associated with increased risk of heart disease in epidemiological studies, and the results of laboratory investigations have described several biological pathways through which psychosocial factors are thought to influence cardiovascular function and contribute to cardiovascular pathology.
As we consider the potential role of stress management in reversing heart disease, it is informative to assess the status of evidence linking psychological stress with cardiovascular risk.
To address this issue, the NHLBI has supported a program of research that includes basic science, epidemiological studies, laboratory investigations, and clinical trials.
It is well known that exercise tolerance tests are useful in diagnosing coronary heart disease by revealing whether exercise results in myocardial ischemia (reduced blood flow to the heart). Similarly, studies of patients subjected to controlled mental stress in a clinical laboratory show unambiguously that mental stress can cause myocardial ischemia and that negative emotions such as anger can have similar effects. Patients who respond to mental stress with myocardial ischemia are called "mental-stress-positive." Data from a large NHLBI-initiated study, the Psychophysiological Investigations of Myocardial Ischemia, showed that heart patients who are mental-stress-positive during clinical stress testing also are more likely to experience myocardial ischemia in the course of everyday life. More important, data from this study published last month show that patients who were mental-stress-positive were more likely to die during the 5 years after mental stress testing than other patients. This finding confirms and extends the evidence from three previous studies conducted at Duke University, Yale University, and the Uniformed Services University of the Health Sciences, which showed that mental-stress-positive patients are at increased risk of various cardiac events, including unstable angina, repeat heart attacks, and need for coronary revascularization.
However, definitive evidence that stress management approaches can influence the course of heart disease must come from randomized, controlled clinical trials that track progression of disease, reduction of new heart attacks, or increased longevity as a result of stress management interventions. Among these, clinical trials that involve death as the primary outcome are the gold standard, and no stress management trials to date have been conducted at this level. Furthermore, although the NHLBI and others have funded a number of clinical trials involving stress management either as a stand-alone intervention or as a component of a broader program of lifestyle change, it is generally acknowledged in the published scientific literature that their results can be regarded only as preliminary. There are several methodological reasons for this, including the fact that combining stress management interventions with other behavioral or rehabilitation strategies makes it difficult to disaggregate their relative contributions to observed outcomes. Clinical trials conducted by different teams involve interventions differing in intensity or duration and may target different psychosocial characteristics, making it difficult to compare their results. Nonetheless, a recent review of a variety of treatment strategies in randomized clinical trials showed that patients derive significant benefits when psychosocial interventions are added to usual medical care.
One carefully conducted clinical trial, although relatively small and preliminary, offers some of the best evidence that stress management may be beneficial for patients with coronary heart disease. The study, funded by the NHLBI and conducted at Duke University, showed that patients who participated in a 4-month stress management intervention program experienced a significantly lower rate of recurrent heart attacks, need for revascularization, and death during the ensuing 3 years, compared with patients who did not receive the intervention. In addition, the data showed that patients who were at highest risk because they experienced many episodes of myocardial ischemia in daily life benefitted substantially from stress management: the number of ischemic episodes was reduced greatly, suggesting that it may be possible to identify patients who are most likely to benefit from such interventions. Earlier this year, the study provided an update of its results, which showed that the benefits of stress management tended to be sustained over a 5-year period, albeit at a reduced level. It also showed that stress management can be economically viable, as the medical expenditures of patients in the stress management group were significantly lower than expenses of patients receiving usual care.
As mentioned previously, this and other studies have several limitations, including small sample size, reliance on relatively "soft" clinical outcome measures, and partial randomization. Nonetheless, the extensive data collected for these patients on mental-stress-related cardiovascular function in the clinical laboratory as well as in daily life have provided the necessary foundation to undertake a trial involving a larger number of patients, which is under way today. Two hundred and ten patients with documented coronary heart disease will undergo comprehensive biomedical and psychosocial evaluation, followed by random assignment to usual care, aerobic exercise, or a stress management intervention. The study will provide new insights into the clinical benefits of exercise and stress management, as well as add to our knowledge of the biological pathways through which stress affects heart function.
The question of whether "reversal of heart disease" is feasible has been a subject of considerable interest and research. Atherosclerosis in coronary arteries is a complex condition involving deposition of cholesterol, structural changes in the lining of the arterial wall, inflammation, and calcification, which together affect vascular structure and function. Aggressive lowering of blood cholesterol levels results in beneficial changes in many of these aspects—vascular function and blood flow are improved, with an associated decrease in the risk of coronary events. However, reversal or regression in the sense of returning to a disease-free state does not occur. Numerous research studies have shown the benefits of lipid-lowering drugs on coronary artery function. Moreover, a small number of clinical trials involving lipid-lowering via intensive dietary modification have shown similar success. One of these, the Lifestyle Heart Trial, included stress management as part of the intervention. Its author, Dr. Dean Ornish, is here today. While intensive risk factor modification through lifestyle changes has shown some success in stabilizing coronary function and reducing cardiovascular risk, it is not possible to know to what extent stress management contributes to the observed results.
To assess the present status of stress management interventions generally, it is also informative to examine the results of studies in individuals with high blood pressure, a very well-established risk factor for coronary heart disease. The NHLBI has supported a series of clinical trials in this area, which has been one of the most intensive targets of investigation for stress management. The most definitive review article on this subject was written by David Eisenberg, who reviewed more than 800 studies and selected 26 that met scientific standards for evidence-based medicine. The results of the analysis, involving 1264 patients, showed that blood pressure was reduced by only 2.8 mm Hg systolic and 1.3 mm Hg diastolic, results which were not significantly different from changes observed in patients assigned to control or "sham" therapies. Similar conclusions were drawn by Podszus and Grote, who later published a review of a more narrowly defined set of stress management studies. One of the larger stress management studies was conducted within the NHLBI-initiated Trials of Hypertension Prevention, involving 562 individuals with blood pressures initially in the high-normal range, which found no statistically significant differences between treatment and control conditions after an 18-month intervention program.
Some of the studies published since completion of these reviews have shown beneficial effects, but their size is too small to change the general conclusions of the earlier review by Dr. Eisenberg. The status of knowledge concerning the effects of stress management on blood pressure reduction, a condition that has been studied more extensively than atherosclerosis, suggests that developing effective stress management interventions for coronary heart disease patients will require continued efforts and perseverance.
In conclusion, what can we do today? We believe that definitive evidence of beneficial effects of stress management on progression of heart disease is not currently available. However, because the evidence of acute effects of stress on cardiac events is well-established, and because the results of the initial clinical trials of stress management interventions for patients with established coronary disease appear promising, it seems prudent to integrate stress management approaches with cardiac rehabilitation programs for patients who want to avail themselves of these interventions. Doing so may improve quality of life and promote lifestyle changes as well as adherence to medical regimens. We do know with certainty that altering several other behavioral risk factors—namely high-fat diets, smoking, sedentariness, and overweight—can play a very substantial role in reducing heart disease. Attention to these areas would benefit the public health.
I would be pleased to answer your questions on this subject.
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Last revised: May 31, 2002