Jeffrey Kwong

According to the Centers for Disease Control and Prevention, cardiovascular disease is the most common cause of death in the United States, accounting for roughly one in four deaths.[1] Important risk factors include age as well as high blood pressure and diabetes mellitus, which are most common in the elderly, further increasing the risk of cardiovascular disease in individuals over 65. Due to a recent increase in life expectancy, cardiovascular disease has come to the forefront of public health as a significant cause of death. While various preventions have long been touted to reduce the incidence of cardiovascular disease, further research is needed to establish their efficacy in order to manage the expected rise in the disease’s incidence.

In treating cardiovascular disease, preventive measures play a critical role. Strokes and heart attacks, the primary outcomes of the disease, occur as sudden episodes with a high chance of death. Other effects include permanent paralysis, infarction, and death of tissue due to blocked blood flow. Thus, in addition to treatments for strokes and heart attacks, much attention has been focused on prevention of the underlying disease. In the medical practice, these preventive measures are divided into primary and secondary categories. Primary prevention refers to steps taken to lower an individual’s risk of an initial adverse cardiac event, while secondary prevention refers to the therapies that decrease the probability of recurring events. According to Dr. Robert Harrington of the Stanford Cardiovascular Institute, both types of prevention are especially important in the elderly, and a daily dose of aspirin is particularly effective.

“Aspirin reduces secondary risk in older and younger patients. Primary risks are more difficult to interpret, but when men start approaching their mid 50s, the benefits [of aspirin] seem to outweigh the increased risk of bleeding. For women, primary prevention using aspirin doesn’t seem to outweigh the risks until women reach their mid 60s,” Harrington noted.

In women over 65, daily low doses of aspirin have been shown to result in a 30% risk reduction in ischemic stroke and a 34% risk reduction in myocardial infarction, the death of heart cells most often caused by obstruction of the coronary artery. In younger women, however, aspirin has not been shown to significantly reduce the risk for major cardiovascular events. Due to the adverse side effects, including increased risk of gastrointestinal bleeding, and the lack of a conclusive benefit, daily aspirin is not recommended for younger women.[2] Men have a higher chance of developing cardiovascular disease, with 1.6 times more cardiovascular deaths in 2009 occurring in men than in women.[3] Accordingly, preventative aspirin is recommended in men at an earlier age.

Several other medications have been prescribed for cardiovascular disease prevention, including hormone replacement therapy and anticoagulants. For fifty years, hormone replacement therapy was recommended as a primary preventive measure in post-menopausal women based on observational evidence that exogenous estrogen decreased the risk of cardiovascular disease. However, a 2002 study by the Women’s Health Initiative concluded that estrogen therapy led to an increased risk for invasive breast cancer as well as increased incidence of coronary heart disease and stroke, ultimately resulting in the termination of the trial.[4] As such, hormone replacement therapy is no longer recommended as a preventive measure for cardiovascular disease in women.

Anticlotting medications have seen much greater success. Numerous anticoagulants are available on the market, and others such as Vorapaxar and Elinogrel are currently undergoing clinical trials. However, like aspirin, these drugs augment the risk of hemorrhage because they interfere with the clotting effects of platelets. Harrington notes, “it’s really a balance between preventing blood clots and heart attacks and increasing the risk of bleeding.”

With respect to the elderly, Harrington cautions that the effects of many preventative measures are not well established in older patients because of the lack of older subjects in randomized clinical trials. Elderly patients form a significant portion of the target population for preventive drugs, but they are also likely to have a different disease profile than the younger patients on whom most clinical trials are performed. Elderly patients have an increased likelihood of comorbid conditions, such as kidney and liver disease, changing the effectiveness of preventive measures. Moreover, patients with multiple conditions are more likely taking multiple medications, leading to potential unforeseen drug interactions. Thus, clinical studies that do not enroll elderly subjects fail to test the effects of the preventive drugs in a population likely to have different physiological responses from the test population. These trials lack external validity, ultimately leading to a dearth in the medical knowledge about preventions for a significant portion of patients. Consequently, Harrington asserts that future studies must be targeted toward the elderly.

As the global life expectancy continues to increase in the coming years, cardiovascular disease will undoubtedly play a larger role in global public health. While a number of current treatments are successful, Harrington warns, “we are prepared, but insufficiently [for the anticipated worldwide increase in the incidence of cardiovascular disease].” Moving forward, new methods and further studies are needed to better equip individuals with the tools and knowledge to tackle the healthcare requirements of an ever-older population.

 

Dr. Robert Harrington is Arthur L. Bloomfield Professor of Medicine, Chairman of the Department of Medicine at Stanford University, and Co-Director of the Stanford Cardiovascular Institute. His research interests include evaluating antithrombotic therapies to treat acute ischemic heart disease and to minimize the acute complications of percutaneous coronary procedures. He recently served as a member and the chair of the Food and Drug Administration Cardiovascular and Renal Drugs Advisory Committee.