Baby and Coated Aspirin May Not Reduce Risk of Stroke

February 2003 - The majority of patients who take baby or coated aspirin to prevent strokes are not getting the blood-thinning results they may need to help avoid these health threats, according to preliminary research presented at the American Stroke Association's 28th International Stroke Conference. The American Stroke Association is a division of the American Heart Association.

"While research has established that aspirin reduces the risk of stroke in patients with cerebrovascular disease, the optimal dose and formulation still remains somewhat unclear," according to Mark Alberts, M.D., the study's lead author and director of the Stroke Program at Northwestern Memorial Hospital. "This study is significant in that it points researchers in the right direction showing how we can maximize the effectiveness of aspirin."

Northwestern investigators collected data on aspirin dose, type (coated or uncoated), demographic factors, and homocysteine level on in-patients and out-patients with cerebrovascular disease, including ischemic stroke, transient ischemic attacks (TIAs) and stenosis or blockage of a cerebral artery. Antiplatelet effects of aspirin were measured using a machine about the size of a coffee maker called a PFA 100 which can quickly, easily and reliably measures platelet function in response to aspirin.

Researchers collected data on aspirin dosage and formulation in the following groups of patients.

  • 39 patients took a baby aspirin (81 mg); 56% of this patient group did not show an antiplatelet effect.
  • 87 patients took an adult aspirin (325 mg); 28% did not show an antiplatelet effect.
  • 40 patients took coated aspirin; 65% experienced no antiplatelet effect.
  • 88 patients took uncoated aspirin; 25% experienced no antiplatelet effect.

This study indicates that adult aspirin produces more blood-thinning results than baby and/or coated aspirin. Results also suggest that age and gender play a role in a person's response to aspirin. Preliminary analyses show that aspirin was less effective at thinning blood in older patients and is more effective among women than men.

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A stroke or "brain attack" occurs when blood circulation to the brain becomes interrupted. The most common type of stroke, ischemic stroke, occurs when an artery narrows or a blood clot blocks blood flow in an artery supplying the brain. A clot can form because of sluggish blood flow through a vessel narrowed by fatty deposits. The goal of aspirin is to thin the blood, thereby reducing the risk of blood clots.

"The long-term goal of this line of research is to determine if we can better tailor the type and strength of aspirin to maximize its effects as a clot-busting agent," said Dr. Alberts. "To ensure aspirin is truly helping those that make a commitment to taking it every day, routine testing of antiplatelet effects may be necessary."

Dr. Alberts and his colleagues plan to continue their research of dose-adjusted aspirin and how PFA results correlate with clinical events.

Co-authors include: Deborah Bergman, MS, FNP, Elise Molner, RN, and Jun Teruya, M.D., Northwestern Memorial Hospital; Borko Jovanovic, MS, PhD, and Issei Ushiwata, Northwestern University's Feinberg School of Medicine.

Mark Alberts, M.D. also added:

  • "Stroke is the third leading cause of death in the United States. Each year, approximately 750,00 patients have a stroke and 165,000 of them die. Increasing age is a major risk factor for stroke, so as our population ages, strokes become even more common."
  • "We know that many patients who have a stroke had been taking daily aspirin. So the question came up: Why is aspirin failing in so many patients?"
  • "These study results are surprising and unexpected. They have huge public health implications because this could really change how aspirin is given routinely throughout the country, if not the world. This opens the door to the idea that perhaps aspirin should be given as a dose adjusted medication."
  • "Certainly we're not advocating that anyone change their dose of aspirin or stop taking their aspirin. They need to consult with their own physician and healthcare providers before they do anything. However, it's important that people understand aspirin does not work in everyone. There are tried and true methods that have been shown to reduce the risk of stroke, which include controlling your blood pressure and diabetes, stopping smoking, eating right and exercising."
  • "The message for patients is clear: do not rely on taking aspirin alone for reducing the risk of stroke. Other things must be done."

Northwestern Memorial Hospital (NMH) is one of the country's premier academic medical centers and is the primary teaching hospital of Northwestern University's Feinberg School of Medicine. Northwestern Memorial was ranked as the nation's 5th best hospital by the 2002 Consumer Checkbook survey of the nation's physicians and is listed in the majority of specialties in this year's US News & World Report's issue of "America's Best Hospitals."

Source: Northwestern Memorial Hospital