Aspirin is a unique drug, the prototypical two-edged sword of pharmaceuticals. It has the capability of stopping platelets, the sticky elements in our blood, from forming clots that cause strokes and heart attacks when arterial plaques rupture, but it increases the risk of serious bleeding into the brain or from the GI tract. Despite these powerful properties, aspirin is available over the counter and is very cheap, thus anyone can take it in any dosage they want.
Who Should Take Aspirin?
For the last five years I’ve been advising my patients who have no evidence of atherosclerotic vascular disease against taking aspirin to prevent heart attack and stroke. Several comprehensive reviews of all the randomized trials of aspirin had concluded by 2011 that
The current totality of evidence provides only modest support for a benefit of aspirin in patients without clinical cardiovascular disease, which is offset by its risk. For every 1,000 subjects treated with aspirin over a 5-year period, aspirin would prevent 2.9 MCE and cause 2.8 major bleeds.
(MCE=major cardiovascular events, e.g. stroke, heart attack, death from cardiovascular disease)
Dr. Oz, on the other hand, came to St. Louis in 2011 to have lunch with five hundred women and advised them all to take a baby aspirin daily (and fish oil, which is not indicated for primary prevention as I have discussed here). When I saw these women subsequently in my office I had to spend a fair amount of our visit explaining why they didn’t need to take aspirin and fish oil.
After reviewing available data, the FDA this week issued a statement recommending against aspirin use for the prevention of a first heart attack or stroke in patients with no history of cardiovascular disease (i.e. for primary prevention). The FDA pointed out that aspirin use is associated with “serious risks,” including increased risk of bleeding in the stomach and brain. As for secondary prevention for people with cardiovascular disease or those who have had a previous heart attack or stroke (secondary prevention), the available evidence continues to support aspirin use.
Subclinical Atherosclerosis and Aspirin usage
As I’ve discussed previously, however, many individuals who have not had a stroke or heart attack are walking around with a substantial burden of atherosclerosis in their arteries. Fatty plaques can become quite advanced in the arteries to the brain and heart before they obstruct blood flow and cause symptoms. In such individuals with subclinical atherosclerosis aspirin is going to be much more beneficial.
Guided Use of Aspirin
We have the tools available to look for atherosclerotic plaques before they rupture and cause heart attacks or stroke. Ultrasound screening of the carotid artery, as I discussed here, is one such tool: vascular screening is an accurate, harmless and painless way to assess for subclinical atherosclerosis.
In my practice, the answer to the question of who should or should not take aspirin is based on whether my patient has or does not have significant atherosclerosis. If they have had a clinical event due to atherosclerotic cardiovascular disease (stroke, heart attack, coronary stent, coronary bypass surgery, documented blocked arteries to the legs) I recommend they take one 81 milligram (baby) uncoated aspirin daily. If they have not had a clinical event but I have documented by either
- vascular screening (significant carotid plaque)
- coronary calcium score (high score (cut-off is debatable, more on this in a subsequent post)
- Incidentally discovered plaque in the aorta or peripheral arteries (found by CT or ultrasound done for other reasons)
then I recommend a daily baby aspirin (assuming no high risk of bleeding).
There are no randomized trials testing this approach but in the next few years several large aspirin trials will be completed and hopefully we will get a better understanding of who benefits most from aspirin for primary prevention.
Until then remember that aspirin is a powerful drug with potential for good and bad effects on your body. Only take it if you and your health care provider have decided the benefits outweigh the risks after careful consideration of your particular situation.