And cessation causes cardiovascular risks to skyrocket, experts say.
Daily aspirin use provides no long-term cardiovascular benefit and instead, can significantly increase the risk of major adverse cardiovascular events (MACE), according to researchers.
Further results from the ASPREE clinical trial, an ongoing longitudinal study of the impacts of daily aspirin use, have confirmed the initial findings published in 2018.
The initiation of daily aspirin was associated with an 11% lower MACE risk but, after stopping the medication, those in the aspirin group experienced 18% more MACE.
This included a 25% higher rate of heart attacks.
Researchers found no long-term cardiovascular benefit from taking aspirin, either during the medication trial or over the lengthy post-treatment follow-up.
Aspirin use was also associated with 24% higher risk of major haemorrhage, 43% higher risk of upper gastrointestinal bleeding and 25% higher risk of other bleeding sites.
The increased risk of major bleeding during the trial largely returned to baseline risk after medication cessation.
The original cohort consisted of nearly 20,000 participants from Australia and the US, most of whom were aged 70 or over.
They had no history of cardiovascular disease events, dementia or independence-limiting physical disability at enrolment (2010-2014).
Participants were randomly allocated to daily 100mg aspirin or placebo and were followed up for almost five years.
At the conclusion of the study period, around 16,000 participants consented to continue follow-up as part of the extension trial.
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The Monash University-led study conducted annual in-person visits and six-monthly calls over both the original trial and the extension, for a combined median follow-up period of 8.3 years.
Researchers proposed several explanations for the findings, including that ceasing aspirin may have removed any short-term protective effects or temporarily increased clotting risk.
They also proposed that aspirin may have delayed cardiovascular events rather than prevented them, or that long-term changes in arterial plaques might have triggered later events.
Professor Rory Wolfe, biostatistician and statistical director of the Monash University clinical trials centre, told media that the secondary analysis confirmed the insights of the initial investigation.
“The overall findings from the original trial suggested that the long-term use of aspirin may not only fail to provide cardiovascular protection in healthy older adults but also significantly increase the risk of hazardous bleeding complications,” he said.
Dr Andrew Tonkin, head of the cardiovascular research unit at the Department of Epidemiology and Preventative Medicine at Monash University, told media that some may still benefit from taking aspirin for primary cardiovascular prevention but should carefully consider the risks and benefits in consultation with their GP.
