Aspirin may not always be the therapeutic agent it seems for preventing stroke and heart attack. In fact, among patients who exhibit a resistance to aspirin, the risk of a severe stroke is higher than among those who are not resistant. The findings were revealed in a study led by Mi Sun Oh, MD, of Hallym University College of Medicine in South Korea.

Oh’s study, which found that stroke size appears larger among individuals with aspirin resistance, reviewed 310 people who had an ischemic stroke, and had been taking aspirin for at least 7 days before the first stroke symptoms.

Among the study subjects 27.7% were resistant to aspirin. A media release from the American Academy of Neurology (AAN) reports that within members of the aspirin-resistant group, the median stroke severity score was four, with scores ranging from three to 11, where scores from one to four indicate a minor stroke and scores from five to 15 indicate a moderate stroke. For those who responded to aspirin, the average stroke severity score was three, with scores ranging from one to six. The people who were aspirin resistant also had larger areas of the brain affected by the stroke, as measured by MRI diffusion weighted imaging, with infarct size of 2.8 cc compared to 1.6 cc for those who responded to aspirin.

In the AAN media release Oh notes that identification of people who are likely to be resistant to aspirin may eventually be possible, and those individuals may be able to receive higher doses or different drugs to prevent blood clots.

“However, we need better ways to identify people with aspirin resistance before any changes can be made. For now, people who are taking low-dose aspirin to prevent blood clotting and stroke should continue to do so,” Oh says.

[Source: American Academy of Neurology]