Just about everyone agrees that aspirin helps to prevent heart attacks by keeping clots from forming, but a major side effect of daily aspirin is increased risk for bleeding. Almost all heart attacks are caused by clots blocking blood flow to the heart. However, a review of 13 studies on nearly 165,000 adults without heart disease and a mean age of 62, showed that five years of taking aspirin every day increased virtually the same percentage of major bleeding episodes as it reduced the incidence of heart attacks (JAMA, Jan 22, 2019;321(3):277-287).
This means that the number of lives that were saved by aspirin decreasing clotting to cause heart attacks was no better than the number of lives that were lost by aspirin causing bleeding to cause strokes and stomach bleeds. The researchers showed that they would need to treat 265 people with daily aspirin to prevent one heart attack, while they needed to treat only 210 people with daily aspirin to cause a major bleed into the brain or gastro-intestinal tract. The absolute risk reduction of fatal and non-fatal heart attacks and strokes was 0.38 percent, compared to the increased risk of 0.47 percent for a major bleeding into the brain or gastrointestinal tract.
Another study found that the number of diabetic lives saved from heart attacks and clotting strokes was offset by the number of diabetics who died from major bleeding into the brain, eyes, stomach, and other places (N Engl J Med. Oct 18, 2018; 379:1529-1539). Diabetes is among the strongest risk factors for suffering heart attacks in North America today, with more than 68 percent of diabetics, age 65 or older, dying from some form of heart disease and 16 percent dying of stroke. The 15,480 adult diabetics who had no obvious heart disease were placed on either 100 mg of aspirin per day (a little more than one baby aspirin) or a placebo. Over the next 4.7 years, a heart attack or clotting stroke occurred in 8.5 percent of the aspirin group, compared to 9.6 percent of the placebo group. This appears to be a significant protection, but major bleeding occurred in 4.1 percent of the aspirin group, compared to 3.2 percent in the placebo group. This is a also a significant difference and shows that whatever advantage was gained by the anti-clotting benefit of aspirin was offset by the bleeding that aspirin can cause, primarily into the brain and intestinal tract.
Data on Aspirin Preventing Heart Attacks Taking aspirin daily for three years is associated with a small reduction in heart attacks only in people who have had previous heart attacks, but not in those who had not had a previous heart attack, and the people most likely to benefit from taking aspirin daily are those 50 to 70 years old (Clin Cardiol, May 2017; Am J Med, Feb 2015;128(2):137-43). The AHA recommends that you take daily aspirin only if your chance of developing a heart attack in the next 10 years is greater than five percent (Ann Intern Med, June 21, 2016;164(12):826-35). They do not recommend that most people over 70 take aspirin regularly because of the increased risk for bleeding.
Factors that put you at high risk for a heart attack include:
• A previous heart attack or stroke
• Previous heart bypass surgery
• Angina (chest pain due to coronary artery disease)
• Diabetes and at least one other heart disease risk factor such as smoking or high blood pressure
• A stent in the arteries leading to your heart. Stents increase risk for clots for the rest of a person’s life. Almost all patients with stents are prescribed some type of anti-clotting medication.
How Aspirin May Help to Prevent Heart Attacks A heart attack and most strokes are not caused by narrowed arteries. They are caused by a sudden complete blockage of blood flow to the heart or brain. First a plaque breaks off from the inner lining of an artery leading to your heart or brain. Then that spot bleeds and a clot forms. Then the clot extends to block completely all blood flow to the heart or brain. The heart muscle then suffers from lack of oxygen and dies. Aspirin helps to prevent blood clots from forming and therefore helps prevent heart attacks and strokes. When a patient is at very high risk for forming clots, doctors often prescribe other drugs with aspirin such as clopidogrel, prasugrel or ticagrelor.
If you have sudden chest pain or headache and think that you may be having a heart attack or stroke, dial 911. You are likely to need far more treatment than just taking aspirin. Often emergency technicians do give aspirin while they are rushing you to a hospital, or after you enter an emergency room with a suspected heart attack. If you are having a stroke, aspirin can harm you because some strokes are caused by bleeding and aspirin increases bleeding.
People Who Should Not Take Aspirin You should not start aspirin therapy without first consulting your doctor. You should not take aspirin if:
• You are at increased risk for bleeding for any reason, particularly to the stomach, intestines or brain
• You drink alcohol regularly. Taking aspirin and drinking alcohol markedly increases risk for stomach and intestinal bleeding.
• You engage in activities in which you are at risk for banging your head, which could result in bleeding into your brain
• You are allergic to aspirin
Caution About Stopping Aspirin Never stop taking aspirin suddenly. You can suffer rebound increased risk from stopping aspirin which puts you at increased risk for a heart attack. If you are going to stop taking aspirin after taking it for a while, your doctor will tell you how to gradually taper your dose of aspirin.
Lifestyle Factors that Decrease Risk for Clots What you eat and what you do influence your susceptibility to forming clots. You can decrease your risk for clotting by:
• losing excess weight
• avoiding smoking and smokers
• keeping diabetes well controlled
• lowering high blood pressure
• lowering high cholesterol
• limiting salt
• following a heart-healthy diet with plenty of vegetables, fruits, whole grains, beans, nuts and other seeds
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