It’s been well proven that a low dose of aspirin every day, as little as 50 mg, helps prevent heart attacks in those who already have heart disease. But should healthy older adults take daily Aspirin? Is the benefit for those without established heart disease greater than the risk from side effects that they might experience?
Aspirin is an old drug...
Aspirin, also known as acetylsalicylic acid or ASA, has been around for a long time. It was originally extracted as salicylic acid from white willow bark or leaves by making the plant into a tea that would be taken to relieve pain and fever, and has been used this way since the middle ages. In the 5th century BC, the Greek physician, Hippocrates, described using willow for signs of inflammation: redness, heat, swelling and pain, and there are descriptions of its use in ancient Arab and Roman herbal texts. In the 1800’s chemists learned to react the salicylic acid derivative, sodium salicylate (often found these days in aspirin creams), with acetyl chloride creating acetylsalicylic acid (ASA) that was easier on the stomach and just as effective for pain and inflammation. The first Aspirin tablet, as we know it, was marketed in 1899.
But is has new uses
It wasn’t until the 1970’s that chemists really began to understand how Aspirin works. It reduces pain and inflammation by blocking the action of enzymes, called Cox-1 and Cox-2, that are needed to make hormones called prostaglandins. Prostaglandins create inflammation, redness, swelling and pain in response to an injury. But Prostaglandins are also needed to create the thick layer of mucous that protects the stomach, and this is why taking aspirin can lead to stomach problems. Many people take aspirin in a form that has been coated to prevent it from dissolving in the stomach, causing it to dissolve in the intestines instead. However, these coatings have not been proven to actually make a difference in the risk of bleeding caused by aspirin. This is because the problem is that Aspirin blocks the production of protective mucous coating in the stomach, not because the drug itself irritates the stomach. The coating may reduce symptoms such as heartburn, however, where the stomach contents are regurgitated back up the esophagus, causing burning and irritation.
The other important action of aspirin that was discovered recent years, is its ability to reduce the “stickiness” of platelets in the blood. Platelets are the first stage of creating a blood clot so making them less sticky means clots will not form as readily. People sometimes refer to this action as “thinning” the blood. Heart attacks and most strokes are caused by a clot forming inside the artery, blocking blood flow to part of the heart muscle or brain. Without oxygen supply from blood, the tissue in the blocked area quickly dies and stops working, resulting in a heart attack or ischemic stroke.
Only very low doses of Aspirin are needed to interfere with platelet stickiness, much lower doses than are needed for pain and inflammation. Platelets that are exposed to Aspirin are changed permanently so, to recover from the blood thinning effect, new platelets need to be made and it takes several days to make enough to regain activity. This is why Aspirin needs to be stopped for about 4 days before a surgery or other procedure where we need blood clotting action to prevent excessive bleeding. Theoretically, an Aspirin could be taken every 3 or 4 days and still work as well to prevent heart attacks, but that’s a recipe for forgetting! This is why doctors recommend taking a very low dose, usually 80 mg, every day. But if you miss a day once in a while, it’s good to know that it’s still working.
Who should take Aspirin?
So, back to my original question: is it a good idea for healthy older adults to take an Aspirin a day help to prevent heart attacks? Many have assumed that it would be, just as it is for those who have already had a heart attack. However, we also have to consider the potential for stomach problems, particularly the risk of severe, life-threatening bleeding.
A new Australian/US joint study that answers this question was just published in the New England Journal of Medicine. The study looked at 20,000 healthy older adults who had no chronic diseases or increased risk of heart attack, with an average age of 74. The results? A daily Aspirin did not increase “disability free survival” in those who took it, compared to those who took a placebo (non-drug sugar pill), but the Aspirin group had a higher risk of severe bleeding in the digestive system and brain. Severe bleeding, or hemorrhage, in the brain gives the second, less common type of stroke, called hemorrhagic stroke.
So, if you are taking a daily low-dose Aspirin but have never had a heart attack, talk to your doctor about whether you should continue. You could be getting more risk than benefit. And be aware that a black, tarry-looking stool suggests that you may be losing blood somewhere in the digestive system, although a few medications can cause a black-coloured stool, such as iron pills and Pepto Bismol. If you take Aspirin, check your stool before you flush. If it looks like it was mixed with black tar, see your doctor right away.
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