Not only has aspirin been used for over a century to relieve pain, but recent research has also suggested its beneficial role for many heart patients.  The risk-lowering effects of aspirin have been identified in people who already have cardiovascular disease (e.g., coronary artery disease or high blood pressure). For healthy people, the potential cardiovascular benefits of a daily aspirin have yet to be determined.

First, aspirin is used to reduce the risk of heart attack because it prevents the formation of potentially dangerous blood clots. Aspirin’s ability to lower the risk of heart attack may be due to its anti-inflammatory properties. Recent studies suggest that inflammation, which aspirin can reduce, plays a large role in the development of “hardening of the arteries” (atherosclerosis). The C-reactive protein test, a marker for inflammation, has shown elevated levels of this substance in some patients with acute coronary events (e.g., heart attack or unstable angina).

Second, aspirin can reduce damage to the heart during a heart attack. The aspirin should be chewed rather than swallowed, and is best taken within 30 minutes of the onset of the attack.

Third, research has shown aspirin to be helpful in protecting people from strokes and mini-strokes (transient ischemic attacks) caused by blockages in the blood vessels of the brain. However, people are strongly encouraged to talk to their physician before beginning to take aspirin routinely, because aspirin may also increase the risk of another type of stroke (hemorrhagic) caused by bleeding into and around the brain, especially in women.

Aspirin is not for everyone, and it should never take the place of medications or other treatments prescribed by a physician. People are encouraged to speak with their physician about whether aspirin would be helpful for them and, if so, what dosage the physician feels is appropriate.

In the early 1970s, research studies concerning the cardiovascular benefits of taking one aspirin a day began to appear. These studies suggested that a daily aspirin could help to prevent heart attacks. The evidence seemed to be so compelling that many people started taking a daily aspirin, including cardiologists.

Over the years, additional research not only confirmed the benefit of a daily aspirin, but also illuminated other benefits. Research has suggested that aspirin may help prevent a first attack, a second heart attack, a first stroke or a second stroke. Data from the Nurses' Health Study also suggest that daily aspirin could reduce the risk of colon polyps and colon cancer, and data from the New York University Women’s Health Study suggest that it could reduce the risk of some types of ovarian cancer. Furthermore, the National Health and Nutrition Examination Survey (NHANES) and the National Epidemiologic Follow-up Study found a dramatically reduced rate of esophageal cancer among people who took aspirin even occasionally.

It took some extra time to demonstrate the benefit of daily aspirin with physician volunteers in the 1988 Physicians' Health Study because of the study's requirements. The study was designed so that all physicians would take a daily pill without knowing the ingredients of the pill. The researchers designed the study so that one-half of the physicians would be taking aspirin and the other half would be taking a sugar pill. However, some physicians were already convinced of the value of aspirin and were unwilling to stop taking aspirin daily in order to participate in research where they might be getting a daily sugar pill. Therefore, it was somewhat challenging to recruit physicians who were willing to participate in the study. The lead researcher of the now-famous study, Dr. Charles H. Hennekens, remains committed to educating physicians about this topic. He is currently involved with a continuing education program called, "Aspirin in the Prevention and Treatment of Cardiovascular Disease."

Many cardiologists recommend a daily aspirin as a preventative measure for patients with risk factors such as family history of heart disease, elevated cholesterol, lack of exercise and/or poor eating habits. All patients who have established coronary heart disease also take a daily aspirin, unless there is a contraindication. Because aspirin can increase the risk of bleeding in the gastrointestinal (GI) tract, it may be helpful to take only enteric-coated aspirin, and generally take with food. As for the dose, some studies recommend 81 milligrams (a baby aspirin) and some studies recommend 325 milligrams (an adult aspirin). 81 mg will control platelet aggregation for 24 hours, and it is not beneficial to exceed that dose.

In light of these promising findings for heart patients, the American Heart Association (AHA) currently recommends daily aspirin for "patients who have experienced a myocardial infarction (heart attack), unstable angina, ischemic stroke, or transient ischemic attacks (TIAs or 'little strokes') if not contraindicated." For people who have not yet experienced any of these cardiovascular problems, the AHA stated that the decision should be made on an individual basis with your physician.

Unfortunately, not everyone can take a daily aspirin, even if their physician believes it might be beneficial. Some patients are allergic to aspirin, have ulcer disease, a history of intestinal bleeding or a general bleeding tendency from many possible causes. Furthermore, people taking an anticoagulant such as Coumadin should not take aspirin because both medications increase the risk of bleeding. People taking nonsteroidal anti-inflammatory drugs (NSAIDs) are generally discouraged from taking aspirin. Finally, people should not take aspirin if they are pregnant, hypertensive, allergic to certain medications or about to go in for surgery, unless specifically recommended by their physician.

According to the American Academy of Pediatrics, the United States Surgeon General, the Food and Drug Administration, the Centers for Disease Control and Prevention and the National Reye's Syndrome Foundation, children under 19 should never be given aspirin if they have a fever-causing illness. If they have a viral infection, then taking aspirin could increase their risk of a rare but potentially fatal condition called Reye's syndrome. Products containing aspirin or other words for aspirin (e.g., acetylsalicylate, acetylsalicylic acid, salicylic acid or salicylate) should also be avoided in these young people when a fever is present.

Chemically, aspirin is known as the compound acetylsalicylic acid (ASA). It fights pain and inflammation by blocking the enzyme called cyclooxygenase, or COX. When this enzyme is blocked, the body is less able to produce prostaglandin, which is a chemical that signals an injury and triggers pain. For example, if a person bumps his or her head, the damaged tissue in the head releases chemicals to help the person feel that pain. Some of these chemicals are prostaglandins. Therefore, blocking their production will lessen the pain felt from an injury or body ache. Aspirin does not heal the underlying problem causing the pain (i.e., the wound itself), but it can help reduce the number of pain "alerters" traveling through the nerves to the brain.

Not only does blocking the production of prostaglandin reduce pain, but it also prevents the formation of blood clots. Some prostaglandins cause platelets to bind together and form clots. If prostaglandin production is slowed or inhibited, so too is clot formation. Therefore, aspirin belongs to a group of drugs called antiplatelets. These are non-habit-forming medications that prevent the formation of blood clots by decreasing the ability of the platelets to bind together (platelet aggregation). By helping to prevent blood clots, aspirin helps to prevent blockages in the arteries that can trigger a heart attack.

One type of prostaglandin, thromboxane, is known to be particularly affected by aspirin. Even small doses of aspirin completely stop its production. Research has shown that taking one baby aspirin (81 milligrams) a day for 10 days successfully reduced thromboxane levels. While the platelets were still able to “plug” a wound so the person did not bleed to death, the platelets were less “sticky” and therefore less likely to form blood clots. For up to 10 days after a person discontinued aspirin use, its effects were still obvious.

By helping to prevent blood clots, aspirin helps to maintain adequate blood flow through the arteries, thus lowering the risk of a heart attack in both men and women. Furthermore, aspirin has been found to reduce the damage of a current or past heart attack if taken either during or immediately after the attack. A 1997 study published by the American Heart Association reported that up to 10,000 more people would survive heart attacks each year if they took one aspirin tablet at the first sign of the attack. Of the 1.25 million Americans per year who have heart attacks, only 60 to 80 percent of them receive aspirin while in cardiac crisis.

Along the same lines, aspirin may be used under a physician's guidance to help in the treatment of certain types of chest pain, pressure or discomfort called angina. Aspirin therapy has also been shown to be beneficial for patients who have had angioplasty, coronary bypass surgery or atrial fibrillation.