Daily Aspirin Risks May Outweigh Benefits

Healthy adults who take aspirin daily to ward off potential heart disease may suffer more harm than good, according to a new review of studies.

Researchers at the University of Warwick (Coventry, United Kingdom) reviewed data sources that included ten electronic bibliographic databases, contact with experts, and scrutiny of the reference lists of included past studies, with eligible studies restricted to publications from 2008 to 2012. They then used novel methods to reevaluate the balance of benefits and harms of using preventive aspirin. The researchers found that of 2,572 potentially relevant papers, just 27 met the inclusion criteria.

The results showed that regular aspirin intake resulted in the successful avoidance 60–84 major cardiovascular disease (CVD) events and 34–36 colorectal cancer deaths per 100,000 person-years. However, in the same time span, 46–49 major bleeds and 68–117 gastrointestinal bleeds in 10,000 people in a 10-year period also occurred. This translates to a 37% increased risk of stomach bleeding and a 38% increase in the risk of hemorrhagic stroke. The study was published on December 5, 2013, in PLoS One.

“We have found that the benefit from regular aspirin use in primary prevention of CVD is modest, while its use increases risk of hemorrhagic stroke and major and minor bleeding,” concluded lead author Paul Sutcliffe, MD, and colleagues of Warwick Medical School. “We need to be extremely careful about promoting the daily use without fully understanding all the evidence.”

“The risks are finely balanced and for now there is not the evidence to advise people to take it. It would be lovely to say over-50’s should take an aspirin a day and have much less cancer, but the research hasn't yet been done and we should be cautious,” added corresponding author Aileen Clarke, MD. “We need to be extremely careful about over-promoting aspirin.”

Aspirin has an antiplatelet effect by inhibiting the production of thromboxane, which under normal circumstances binds platelet molecules together to create a patch over damaged walls of blood vessels. Because the platelet patch can grow large enough to block blood flow—both locally and downstream—aspirin is also used long-term, at low doses, to help prevent heart attacks, strokes, and blood clot formation in people at high risk of thrombosis. Aspirin may be also be effective at preventing certain types of cancer, particularly colorectal cancer.

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