New guidelines from the US Preventive Services Task Force (USPSTF) are once again taking an axe to the often-heard health axiom: “An aspirin a day keeps the doctor away.”
Weighing the balance of benefits and harms, the USPSTF recommends that for most people, low-dose aspirin (generally recognized as 81 mg, a “baby aspirin”) should not be used for the primary prevention of cardiovascular disease (heart attacks and strokes) or colorectal cancer.
From a cardiovascular standpoint, this recommendation could get a lot of people in serious medical trouble if they don’t understand what “primary prevention” means. If a patient has no clinical evidence of cardiovascular disease but is taking an aspirin to avoid having a heart attack or stroke in the future, that would be termed primary prevention. If the patient has already had either a stroke or a heart attack (or was found to have asymptomatic cardiovascular disease on testing), that same aspirin would be considered “secondary prevention”: the disease has arrived, and now we want to keep it in check and prevent the complications.
If you have established cerebrovascular disease and are taking an aspirin, DO NOT STOP. It’s an important part of making your last heart attack your last heart attack. Here’s why.
Aspirin reduces pain and inflammation, but it also is a blood thinner. Blood clots in two different ways: by the activation of specific clotting proteins found in blood, or by the clumping together of blood cells called platelets — a reaction that is at the root of most heart attacks and strokes, and one that aspirin blocks.
“Cardiovascular disease” typically refers to atherosclerosis build up in the arteries, a kind of scarring caused by diabetes, smoking, high blood pressure and bad cholesterol. Sometimes this atherosclerotic scar tears open, forming a rough spot that attracts a blood clot that then closes off the blood vessel. With little or no blood flow getting past the blockage, downstream tissue — in the brain, heart, your toes, wherever — will die.
Aspirin’s blood-thinning effect on platelets can prevent these clots from laying one low, making it an important secondary prevention for heart attacks and strokes. (If aspirin’s anti-inflammatory effects were strong enough to prevent atherosclerosis from developing in the first place, then it would be deemed to be a primary prevention. Perhaps it does that to a small degree in all patients, but if so, the benefits only outweigh the risks for 50–59-year-olds at intermediate to high risk.)
Additionally, an aspirin is doubly important if you are the owner of a stent — a wire mesh tube placed during an angioplasty procedure, wherein an artery clogged with atherosclerosis is ballooned open. The stent keeps the artery from collapsing back in, but the stent itself can attract a clot; so, once you have one, you’ll need to take a daily aspirin till death do you part. And you’ll also need to be on a more powerful anti-platelet drug (Plavix, Brilinta) for a year or so.
The “risk” in the risk-benefit equation of aspirin is primarily due to bleeding, typically in the gastrointestinal tract — stomach ulcers or elsewhere. (Drugs like aspirin and over-the-counter pain relievers like ibuprofen and naproxen interfere with the stomach’s ability to produce the coating that shields it from its highly acidic contents.) Typically, this gastrointestinal bleeding is more pesky than lethal, but it might well give you the opportunity to be probed up and down by a gastroenterologist armed with a disturbingly long fiber optic tube. Much less common, but much more serious, is bleeding into the brain, which ironically can cause the stroke one may have been trying to avoid in the first place.
The USPSTF did make one exception to the rule, and exceptions can be awkward. They did recommend aspirin as primary prevention for adults aged 50-59 who have a 10% or greater (intermediate-to-high) 10-year cardiovascular disease risk. This is the likelihood that one will experience a heart attack or stroke in the next decade. You can find out what your 10-year CV risk is by using any number of online calculators. Your “score” can help you and your physician make decisions about how aggressively you want to treat your CVD risk factors, or how quickly you want to permanently reduce your stress level by joining what is now nearly the entire U.S. work force in an early retirement.
Besides the 10%-or-higher 10-year CVD risk, qualifiers would have to be at low risk for bleeding, be willing to take a daily low-dose aspirin for “at least” ten years and have a life expectancy of 10 years or more. (There is some life expectancy data on patients with cancer, but otherwise, this would be better answered by an actuary than a physician).
It’s a little unusual to lump cardiovascular disease in with colorectal health, but the USPSTF did it (purportedly to “‘simulate how a doctor and patient make…decisions’ about prevention.”) There is observational data showing that aspirin use reduces the risk of colorectal cancer, but stronger, randomized clinical trials are needed to clarify the effect. This article from the National Cancer Institute will take you further into the debate.
What to do? If you’re taking an aspirin because you’ve already had a heart attack or stroke (or have asymptomatic cardiovascular disease found on testing), stay on it. It’s an important part of warding off a future event. If you’re taking one “just in case,” you might reconsider. If you’re age 50-59, and currently free of CV disease but at intermediate to high risk of acquiring it, take two aspirin and text me in the morning. Please include your colonoscopy report.