Should you be taking a daily aspirin?
First, a little bit of (easy) basic science: we cut ourselves all the time, and nature has given us protection against bleeding to death every time this happens.
The first line of defense is our platelets, small blood particles that go to the site of disrupted blood vessels and plug any small holes, like the little Dutch boy at the dike.
The second and more permanent way bleeding is stopped is that proteins in our blood form clots.
These protective forces can cause harm. Platelets attracted not to a hole in an artery but to an irregular surface such as a cholesterol plaque can block off the artery, causing a heart attack or stroke.
(Unneeded clots can also cause problems – we will discuss that another day.)
Aspirin works to prevent platelets from clumping together. This effect is rapid and effective: a single dose of 81 or 162 mg (“low dose”) aspirin paralyzes all the circulating platelets. Platelets turn over rapidly; you get an entirely new set every 7 days, so a single dose will be effective for a few days only.
Many decades ago, it was shown that daily low dose aspirin started within 24 hours of a heart attack dramatically reduced the risk of another heart attack and stroke. This effect is called “secondary prevention:” preventing a recurrence, and nothing has changed this benefit. If you have coronary disease, you should be on aspirin unless you are at very high bleeding risk.
The problem comes when the prescription of aspirin moves from this valid use to broader use. It seems logical that if aspirin taken after a heart attack prevents another one, taking aspirin before a heart attack should prevent a first one, so-called “primary prevention.”
Aspirin taken this way DOES decrease a first heart attack or stroke, but only by a very small amount. This benefit is typically outweighed by the increased risk of bleeding that comes with aspirin use.
The higher your risk of heart attack or stroke and the lower your risk of bleeding, the more the evidence says to take aspirin. If you have multiple risk factors such as hypertension, high cholesterol, smoke and have a positive family history, and particularly if you have a high coronary calcium score, the more likely you would benefit from daily low dose aspirin.
If your coronary risk is only moderate and if you have had a bleeding ulcer or other serious bleeding, you are better avoiding aspirin.
In between? The old fallback: talk to your doctor!
No known major coronary risk? The risks almost certainly outweigh the benefits.
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