Benefit of ASA in preventing heart attacks and strokes

Apr 15, 2020

By Trevor Shewfelt, Pharmacist at the Dauphin Clinic Pharmacy

"Wow, you guys look like little old men!" Kirk Nyquist and I were trying to videoconference with Zoom. We'd usually meet at CKDM to record our podcast, Reefer MEDness, but like so many things in a COVID-19 world, that has changed. CKDM has wisely barred non-employees from their building. That meant Kirk and I were experimenting with new microphones while trying a videoconference. Our plan was to record separately while videoconferencing to mimic recording together in one room. But like all tech, the set up wasn't smooth. Emily was being my tech support by moving the iPad back and forth to get my head in frame. Meanwhile I kept trying to tap the screen to get the controls right to see and hear Kirk. While we were doing this little Zoom dance, Emily was giggling at us, our glasses and our old codger antics.

Taking low dose ASA is also something many old codgers do. Although low dose ASA is still really good, effective and safe for many things, it might not be quite the panacea we once thought, especially for those over 70.

Let's step back a bit first. ASA does interesting things in the body. It affects the enzyme cyclooxygenase and this decreases the pro-inflammatory chemicals the prostaglandins. We think that decreasing these prostaglandins is what causes ASA to be able to decrease pain and inflammation. We think that the decrease of the prostaglandin E1 in the brain is what causes ASA to be able to decrease fever. ASA also affects platelets. Platelets help your blood to clot. ASA stops the cyclooxygenase enzyme in the platelet from forming thromboxane. This permanently disables the platelet from being able to clot for the life of the platelet, which is 7 to 10 days. This ability of ASA to hinder the blood from clotting is why we give ASA to people to prevent heart attacks and strokes. A blood clot in the wrong place is the cause of many heart attacks and some strokes.

The Heart Research Institute says every 7 minutes someone in Canada dies of heart disease or stroke. If ASA prevents heart attacks and strokes and it is very inexpensive, why shouldn't we put all adults on it? In 2019, the American Heart Association said the heart disease prevention benefit of ASA might not always outweigh the risks including increased bleeding. So yes, ASA prevents heart attacks and strokes, but does it do some bad stuff too. Let's look at an example. People with diabetes are more likely to get a heart attack or stroke than people without diabetes. But, ASA's benefits are nearly a wash in patients with diabetes. Using aspirin for about 7 years may avoid a cardiovascular event in one in 90 patients. That's good, but ASA for 7 years can cause a life-threatening bleed in one in 110 patients. So, for people without a previous heart attack or stroke, ASA doesn't seem to give any extra benefit to people with diabetes.

There are some nuances to be aware of here. We need to talk about primary and secondary prevention. Primary prevention is when a person takes a treatment to try to prevent a disease that has never happened before in that person. Secondary prevention is a treatment to prevent a disease that has already happened from happening again. Starting in the 1980's researchers found that people who had heart attacks and strokes were less likely to have a second heart attack or stroke if they took ASA. That is secondary prevention. Everyone still agrees on using ASA for secondary prevention. ASA definitely still reduces the chances of heart attack and stroke in people who have had one already.

The 2019 American Heart Association statement about ASA and seniors might be the most interesting part. These recommendations were probably at least partially based on a recent study. JJ McNeil et al. published "Effect of Aspirin on All-Cause Mortality in the Healthy Elderly" in the September 16, 2018 New England Journal of Medicine. They looked at healthy people 70 years and over in the US and Australia with no heart disease, dementia or disability. They had 19,114 people enrolled. Half got ASA 100 mg and half got placebo. They were followed for almost 5 years. And the placebo group did not die more often than the ASA group.

What does this study tell us? They looked at healthy older people because they should be the most likely to benefit from ASA. And they didn't. This adds to the evidence that low dose ASA doesn't prevent enough heart attacks and strokes in people without heart disease to justify giving it to everyone.

For primary prevention of heart disease in patients with diabetes, over 70 years old, those with prior gastrointestinal bleeding problems, and with a few other conditions, low dose ASA does not do more good than harm, so is no longer recommended. Also, in general, it is a myth that enteric-coated or buffered ASA causes less GI bleeding. Gastrointestinal bleeding is mainly due to ASA's antiplatelet, anti-prostaglandin and other effects it causes once it is absorbed, and is not due to ASA directly irritating the GI lining which the special coatings might prevent.

If you are over 70 and want to protect your heart, what should you do instead of ASA? You should do the boring things that your doctor has said all along. You should make lifestyle changes like eating more veggies and fruit, go for a walk for 30 minutes a day, quit smoking, and keep taking those blood pressure, cholesterol and diabetes meds that you were prescribed.

Should I throw out my ASA? Of course not. Remember the study participants were surprisingly healthy 70 plus year olds. They had no heart disease, no dementia, no other disabilities. Healthy 70 and 80 years olds exist, but most of the people that age who see me in the pharmacy have partially blocked arteries, and/or a previous heart attack, and/or previous mini-stroke, and/or a stent and/or an irregular heart beat, and and and. We do know ASA is good a preventing a second (or third or fourth) heart attack or stroke. Most of the people I talk to on ASA already have a heart condition of some kind. They should definitely not stop their ASA. If you are on ASA now, talk to your doctor before stopping it. If you've never taken ASA before and want to start, talk to your doctor first.

Emily giggled as I lifted my nose in the air. It wasn't because I was looking down on people. It was so I could look at the iPad screen through the progressive bi-focals at the bottom of my glasses. Emily snickered as Kirk pushed his glasses down his nose to look over them at his laptop. Emily was endlessly amused at the two old men holding their heads at weird angles to try to set up their Zoom videoconference. There are so many new things to learn in this weird COVID-19 world. Videoconferencing with friends and family. Semi-obsessive hand washing. How everything I do makes me look old to my children. Well, maybe not everything is new.

As always if you have any questions or concerns about these products, ask your pharmacist.

The information in this article is intended as a helpful guide only. It is not intended to be used as a substitute for professional advice. If you have any questions about your medications and what is right for you see your doctor, pharmacist or other health care professional.

American Heart Association Guidelines on Aspirin -

NEJM - Effect of Aspirin on All-Cause Mortality in the Healthy Elderly -

Heart Research Institute - Heart disease facts -


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