In this study, ED was a stronger predictor of significant coronary heart disease than any of the traditional office-based risk factors, such as family history, cholesterol levels or blood pressure. ED was also associated with reduced exercise endurance and decreased ejection fraction -- a measure of the heart's pumping capacity.
"This suggests we may need to ask male patients a new set of sensitive questions as part of the evaluation for heart disease," said cardiologist and study director Parker Ward, M.D., assistant professor of medicine and director of the cardiology clinic at the University of Chicago. "The good news is that a decrease in sexual function could provide an additional warning sign for the presence of heart disease."
The study focused on 221 men who had been referred to cardiologists at the University of Chicago for nuclear stress testing, a widely used non-invasive way to detect the extent, severity and reversibility of coronary heart disease. Before cardiac testing began, the men filled out a questionnaire that assessed erectile function.
Almost 55 percent of the men (121 out of 221) suffered from erectile dysfunction. Those men, on average, scored less well on exercise tests and measures of coronary heart disease. They had shorter exercise times, lower treadmill scores, and more frequently had a low ejection fraction.
They also had greater evidence for significant coronary artery blockages during myocardial perfusion imaging -- the portion of the test that measures blood flow to the heart. Forty-three percent of men with ED, compared to 17 percent of tested men without ED, had a myocardial perfusion summed stress score greater than eight, which is "strongly associated with clinically significant obstructive coronary artery disease and a high risk of both cardiac death and nonfatal myocardial infarction," note the authors.
Erectile dysfunction does not cause heart disease, they caution, but it may indicate that the process of arterial damage is well under way.
The risk factors for ED and coronary artery disease are similar, including obesity, diabetes, hypertension, smoking and hyperlipidemia. "As the penile arteries are relatively small in comparison with the coronary arteries," the authors write, "they may be more prone to cause ED with even comparatively small amounts of atherosclerosis."
They caution that there are a number of potential causes for erectile dysfunction, including emotional or psychological components which may not be associated with heart disease. Nonetheless, "the fact that heart disease and ED are linked biologically should come as no surprise," Ward said.
This paper has two important clinical implications, Ward said.
"First, our study identifies a group with a high prevalence of ED, and thus increased communication about this sensitive topic between patients and physicians may lead to increased treatments and improved quality of life for these patients."
"Second, asking patients about their sexual function may help identify those at risk for significant heart disease, allowing physicians to stratify that risk with further testing, and get them engaged in an aggressive program of risk-factor modification or treatment."
Additional authors of the paper, "Prediction of Coronary Heart Disease by Erectile Dysfunction in Men Referred for Nuclear Stress Testing" (Arch. Intern. Med. 2006; 166; 201-206), include James Min, Kim Williams, Tochi Okwuosa, George Bell and Michael Panutich, all from the section of cardiology at the University of Chicago. The study was supported in part by an unrestricted independent medical grant from Pfizer Pharmaceuticals.