You've undoubtedly heard that a baby aspirin a day will help prevent the formation of blood clots that could cause a heart attack or stroke. Well, the aspirin probably won't help you much if you've never had a heart attack or stroke, according to a study published in the March 3 issue of the Journal of the American Medical Association.
But don't throw away your baby aspirin just yet. Even though it may not be right for you today, it might help you prevent cardiovascular problems later in your life, according to Dr. Jeffrey S. Berger, who comments on the study in an editorial in the same issue of JAMA.
Basically, the potential benefit of aspirin depends on your own risk of heart disease, which you must balance against the risks and benefits of aspirin.
"Aspirin continues to have benefit — it decreases cardiovascular events by approximately 20 percent," said Berger, assistant professor of medicine at New York University's Langone Medical Center. "But if your initial risk is low, then your absolute benefit is very low."
Suppose, for example, that your risk of having a heart attack is about 2 percent per year, based on such risk factors as your blood pressure, cholesterol level and family history. If you take a baby aspirin every day and decrease your risk by 20 percent, you'll get your risk down to 1.6 percent — a trivial decrease. If your risk of having a heart attack is 10 percent, however, you'll reduce your risk by 2 points, to 8 percent.
Now the benefit of taking aspirin probably offsets the risk.
"There can be a significant amount of bleeding with aspirin — bleeding in the GI tract and in the brain," Berger said. "That's why it's so important to understand each patient's risk factor profile.
"It's not that aspirin is more effective in one type of patient; it's that the patient with the higher risk-factor profile will obtain greater benefit. It's important to understand risk before you can determine the overall benefit."
The authors of the JAMA study screened nearly 29,000 men and women between the ages of 50 and 75 who were free of cardiovascular disease. Of those they selected, 3,350 had a low ankle brachial index; that's a measure that compares a blood pressure reading taken at the ankle with one taken at the arm. Those whose blood pressure is lower at the ankle than it is at the arm probably have some degree of peripheral artery disease — an early sign of cardiovascular disease.
Half of those 3,350 participants took 100 milligrams of aspirin a day, while the other half took a placebo.
Over the next few years, 357 participants had a heart attack or stroke, but they were evenly divided between the two groups. The aspirin appeared to provide no protection.
And among the 54 participants who experienced brain bleeding severe enough to land them in the hospital, 34 were taking aspirin while only 20 were taking a placebo.
So should you take a baby aspirin every day to reduce your chances of having a heart attack or stroke?
According to Berger, if you've had a heart attack or stroke, a baby aspirin a day — get the enteric, coated kind for less stomach upset — probably will reduce your risk of a recurrence significantly enough to offset the increased risk of internal bleeding that aspirin causes.
"I think it's important to remember that aspirin is an important disease-modifying drug in patients who have established or symptomatic cardiovascular disease," he said. "And if you take aspirin, you should take the lowest effective dose because of the risk-benefit profile. A higher dose does not confer greater benefit, but it does increase risk."
Tom Valeo writes frequently about health matters. He can be reached at firstname.lastname@example.org.