A study published in the Annals of Internal Medicine Sept. 17 suggests daily aspirin could result in a net benefit for some people without established CVD, further muddying the debate over whether aspirin is an effective preventive tool for those without heart disease.
Vanessa Selak, MBChB, PhD, et al.’s findings stand in stark contrast to those of another aspirin study published this May—one that insisted the risk of low-dose daily aspirin outweighed its benefits in the general population. In that meta-analysis, low-dose aspirin—defined as 100 mg per day or less—was linked to a 1.37-fold increased risk of intracranial bleeding and a higher likelihood of subdural or extradural hemorrhage.
Similarly, in a January study published in JAMA, major bleeding rates were 43% higher among aspirin users with no baseline CVD. But aspirin was also associated with an 11% reduction in the composite cardiovascular outcome of CV death, stroke or MI in the same study, throwing the true efficacy of the drug into question.
For their work, Selak and colleagues at the University of Auckland in Auckland, New Zealand, looked at 245,028 adults whose CVD risk was assessed between 2012 and 2016 at a New Zealand primary care clinic. Patients were aged 30 to 79 and had no prior heart disease.
The researchers calculated the net effect of aspirin for each study participant by subtracting the number of CVD events likely to be prevented by aspirin from the number of major bleeds likely to be caused by the drug over five years. Defining one CVD event as an event equivalent in severity to one major bleed, Selak and co-authors found that 2.5% of women and 12.1% of men in the study were likely to see a net benefit from aspirin treatment over five years. Expanding the definition of a CVD event to one equivalent to two major bleeds, that net benefit jumped to 21.4% of women and 40.7% of men.
“Compared with the net harm subgroups, the net benefit subgroups had a higher baseline five-year CVD risk, with higher levels of most established CVD risk factors and lower levels of bleeding-specific risk factors,” Selak et al. wrote in their paper. “Net benefit versus net harm subgroups were clearly demarcated when participants were plotted according to baseline CVD and bleeding risk, and a considerable range was observed in pretreatment CVD and bleeding risks among patients likely to benefit from aspirin.”
Other studies may have provided conflicting information, but the authors maintained that while those studies assessed CVD risk by using risk prediction equations, none assessed bleeding risk in the same way. So how should patients digest the inconsistent data?
“In the end, patients are the ones who must decide, in consultation with their physician, whether to take aspirin,” Selak and colleagues said, noting that in New Zealand, physicians have access to a web-based calculator that provides individualized estimates of aspirin’s benefits and harms for specific patients. It’s a standalone tool right now, they said, but could potentially be integrated on a wider scale in the future.
“Some persons without CVD are likely to derive net benefit from aspirin,” the team wrote. ”They could be identified by using a personalized benefit-harm analysis, and sharing the findings of such an analysis with patients might support more informed decision-making.”
After graduating from Indiana University-Bloomington with a bachelor’s in journalism, Anicka joined TriMed’s Chicago team in 2017 covering cardiology. Close to her heart is long-form journalism, Pilot G-2 pens, dark chocolate and her dog Harper Lee.