Do warfarin and aspirin contribute to stroke occurence?

This study examined the effect of warfarin and aspirin on hemorrhagic stroke risk.

Hemorrhagic stroke constitutes approximately 10% to 20% of all strokes.  It occurs when a blood vessel in the brain breaks, leaking blood into the brain.

Hemorrhagic stroke encompasses several subtypes such as intracerebral hemorrhage ( the most common type, occurs when a blood vessel inside the brain ruptures) and subarachnoid hemorrhage (usually occurs due to the rupture of an artery into the space surrounding the brain).In both cases blood that spills out of the vessels forces pressure on the brain  leading to brain cell damage.

Antithrombotic (drugs that stop blood clotting) drugs have been reported to increase the risk of hemorrhagic stroke relative to no treatment. However, studies directly comparing the risk of hemorrhagic stroke in patients receiving anticoagulant treatment (a therapy that interferes with blood clotting factors such as vitamin K) or antiplatelet drugs (drugs that stop blood cells called platelets from sticking together and forming a blood clot) are scarce.

The aim of this study is to investigate the relationship between use of antiplatelet drugs (aspirin) and anticoagulant treatment (warfarin) with hemorrhagic stroke subtypes in the general population.

This study followed 2,110,327 individuals for an average of 5.8 years. During this time a total of 1,797 incident cases of intracerebral hemorrhage and 1,340 of subarachnoid hemorrhage were identified and verified.
These patients were compared with a group of individuals (10,000) possessing similar characteristics but free from hemorrhagic stroke (control group).

All participants were classified as “current users” if they were taking a drug (aspirin or warfarin) or had taken it within the previous 30 days (prior to the stroke occurrence). Everyone else was classified as a “nonuser.”

Following analysis, researchers concluded that aspirin use was not associated with an increased risk of intracerebral hemorrhage but was associated with a decreased risk of 18% for subarachnoid hemorrhage compared with no therapy. Furthermore, prolonged use of  aspirin (more than 3 years) reduced the risk of subarachnoid hemorrhage by almost 40% compared with no therapy.

On the other hand, warfarin use was associated with a greatly increased risk of intracerebral hemorrhage (2.8 times the odds for intracerebral hemorrhage to occur compared with no therapy).Warfarin use also moderately increased risk of subarachnoid hemorrhage(1.67 times the odds compared with no therapy).

This study concluded that aspirin use is not associated with increased risk of hemorrhagic stroke compared with no therapy. By contrast, warfarin use is associated with a marked increased risk of hemorrhagic stroke compared with no therapy. 

Both aspirin and warfarin carry a risk of side effects and should not be taken without physician consultation.