Aspirin is the gray lady of the medicine cabinet. Aspirin, the medication that has been in use for over 100 years, is tried, true and reliable. Aspirin has been prescribed for a variety of ailments including fever, aches and pains. Aspirin is the standard of care in the treatment of heart disease and stroke. Judging by its longevity and the extent of its use, it would seem that we know all there is to know about aspirin. That assumption would be wrong.
Aspirin’s anti-inflammatory and blood thinning properties are ideally suited for treating an acute heart attack or stroke. Aspirin is usually the first medication given in the ambulance to a patient who is having a heart attack. In addition, there is data going back decades showing that aspirin can prevent a second heart attack or stroke in patients who have already had an event. This is called secondary prevention and aspirin’s role is not controversial and well established. What about primary prevention, trying to prevent a heart attack or stroke in a patient who has not had an event? Here aspirin’s role is much murkier and the data not as solid. A few primary prevention trials of aspirin were done many years ago and showed a small cardiovascular benefit for aspirin, even though the risk for bleeding increases with aspirin use. In 2016 the US Preventive Services Task Force recommended a low dose (81 mg) aspirin for adults aged 50 to 59 years old, who are at high risk for cardiovascular disease. What about patients who are 70 years of age or older, a population known to be at higher risk for cardiac events? Should an aspirin a day be prescribed?
Several large, well done primary prevention trials have recently been published and have added clarity. In a trial of 15,000 patients with diabetes (average age of 63), aspirin lowered the rate of cardiovascular events but increased the risk for major bleeding. There was no reduction in the death rate. The next trial included 12,000 nondiabetic patients with the men over age 55 and the women over the age of 60. These were patients felt to be at low risk for cardiovascular disease. Again, aspirin did not reduce mortality. There was no cardiovascular benefit for taking aspirin and the risk of bleeding was twice as high. The last trial included 17,000 patients all older than 70 years old and without cardiovascular disease. Once again, aspirin gave no benefit with respect to death, cardiovascular events, dementia or physical disability. The risk for bleeding on aspirin was higher. Overall these trials were consistent in showing that aspirin provided minimal benefit and significant bleeding risks. On the scale of benefit versus risk, the risk of aspirin outweighed any benefit in primary prevention. What changed compared to previous primary prevention trials? The difference seems to be that the prevention of heart disease is much better now than in the past. Smoking is less common and the treatment of high blood pressure, high cholesterol and diabetes is better and more aggressive.
What is the correct dosage of aspirin? Even after all of these years, we still do not know for certain. Guidelines recommend a full dose (325 mg) of aspirin for at least one month after a heart attack, a cardiac stent, bypass surgery or a stroke. Then the recommendation is to lower the dose to 81 mg, with the idea that the lower dose confers the same benefit as the higher dose, but with less risk for bleeding. Now a new study questions the efficacy of 81 mg of aspirin. It was found that low doses of aspirin, such as the 81 mg dose, were only effective in protecting against cardiovascular effects in patients weighing less than 150 pounds and had no benefit for those weighing more than 150 pounds. This issue certainly will require further study.
All of these studies were reported in the news accompanied by headlines such as, “Aspirin Flops Big Time in Heart Study. Is it R.I.P. for Aspirin?” This caused a lot of confusion among patients as to whether they should be on aspirin. To clarify, if you are having a heart attack or stroke, take an aspirin and call for help. If you have a history of heart attack, cardiac stent, bypass surgery, stroke, significant plaque in the neck (carotid) arteries, aorta or leg arteries, congestive heart failure or atrial fibrillation then the benefits of aspirin outweigh the bleeding risks. If you do not have any of these conditions, then you should not take aspirin for primary prevention of cardiovascular disease. Instead, you should refrain from smoking, exercise regularly and take a statin and/or blood pressure medication as indicated. Of course if there are any questions, talk over the risks and benefits of aspirin with your doctor.