Oct. 13, 2009
Depression Boosts Heart Disease Risk By Affecting Stress-Induced Blood Flow
Researchers at Emory University School of Medicine have identified a measure of stress-induced blood flow in the heart that explains part of the connection between depression and heart disease.
The results are published in the Oct. 12, 2009 issue of Archives of Internal Medicine.
By studying identical and fraternal twins, scientists led by Viola Vaccarino, MD, PhD, professor of medicine (cardiology), and director of the Emory Program in Cardiovascular Outcomes Research and Epidemiology, aimed to clarify the contribution of genetics to the link between depression and heart disease.
In the twin study, the presence of depression tended to reduce coronary flow reserve, a measure of the ability of small blood vessels in the heart to dilate, but in a way influenced by genetics.
The authors say this is the first study to examine the relationship between major depression and coronary flow reserve. The study included 68 pairs where one twin had major depression and the other did not, seven pairs where both were depressed, and 105 depression-free pairs. All subjects were male Vietnam-era veterans.
Coronary flow reserve was 14 percent lower in fraternal twins with major depression than in their brothers who were not depressed. This association was not present in identical twins.
When examining identical twins, researchers can assign all the differences between them as coming from differences in their environment, since they are genetically the same. If there are no differences in identical twins, but there are in fraternal twins, this is a clue that genes play a role.
The finding suggests that genetic susceptibility influences which individuals with depression will be at increased risk for heart disease.
In addition, the study found that depression may contribute to heart disease risk by affecting the microscopic blood vessels in the heart, rather than the larger arteries that are the focus of procedures such as angioplasty and bypass surgery.
Visual inspection of cardiac scans didn't reveal differences in heart function, Vaccarino says. Previous studies had looked at depression and other measures of heart function, without clear results. Coronary flow reserve is a comparison of blood flow through the heart at rest and under stress, measured with positron emission tomography.
"Coronary flow reserve reflects the ability of small arteries in the heart to relax and dilate in response to increased demand for blood," Vaccarino says. "In daily life, this is how the heart responds to exercise. But in our research, we use the drug adenosine because the body's ability to handle exercise varies from person to person."
Poor function of the heart's small arteries has been linked to atherosclerosis and poor heart disease prognosis in previous studies, Vaccarino says. Problems with these blood vessels may come from processes such as inflammation and oxidative stress. Her group's research has identified genes involved in inflammation that influence both depression and heart disease risk.
Because depression is especially common among younger women with heart disease, Vaccarino says one limitation of the study is that it only examined middle-aged men. She says future genetic research on depression and heart disease risk should and will include women.
V. Vaccarino, J. Votaw, T. Faber, E. Veledar, N. Murrah, L. Jones, J. Zhao, S. Su, J. Goldberg, J.P. Raggi, A. Quyyumi, D. Sheps and J.D. Bremner Major Depression and Coronary Flow Reserve Detected by Positron Emission Tomography. Arch. Int. Med 169, 1668-1676 (2009)
The Robert W. Woodruff Health Sciences Center of Emory University is an academic health science and service center focused on missions of teaching, research, health care and public service. Its components include schools of medicine, nursing, and public health; Yerkes National Primate Research Center; the Emory Winship Cancer Institute; and Emory Healthcare, the largest, most comprehensive health system in Georgia. The Woodruff Health Sciences Center has a $2.3 billion budget, 17,000 employees, 2,300 full-time and 1,900 affiliated faculty, 4,300 students and trainees, and a $4.9 billion economic impact on metro Atlanta.