FRIDAY, Jan. 18 (HealthDay News) -- Heart patients who are resistant to aspirin are four times more likely to suffer a heart attack, stroke or to die, a new Canadian study says.

People who are aspirin-resistant have platelets -- the cells in blood responsible for clotting -- that aren't affected in the same way as platelets in people who respond to aspirin.

Publishing in the Jan. 18 online edition of the British Medical Journal, researchers at McMaster University Health Sciences Centre in Hamilton reviewed 20 studies that included 2,930 people with cardiovascular disease who'd been prescribed aspirin to prevent formation of blood clots. About 28 percent of the patients in the studies were aspirin-resistant.

The analysis revealed that 39 percent of aspirin-resistant patients suffered some sort of cardiovascular event, compared to 16 percent of other patients.

The researchers also found that other blood-thinning drugs, such as Clopidogrel or Tirofiban, did not provide any benefit to aspirin-resistant patients.

Currently, there is no agreed-upon method for identifying aspirin-resistant patients, and there is ongoing debate about why a person may be aspirin-resistant in the first place.

The authors of this latest study said more research is needed to figure out the best way to identify aspirin-resistant patients.

More information

The U.S. Food and Drug Administration has more about the use of aspirin to reduce stroke and heart attack risk.