Quick Facts

• Daily aspirin did not reduce cancer rates in healthy adults over 70 and increased cancer death risk in 8.6-year study
• New research shows aspirin likely does not lower bowel cancer risk during first 5 to 15 years of use
• U.S. Preventive Services Task Force eliminated colorectal cancer prevention from aspirin recommendations in 2022

Daily aspirin does not prevent cancer in older adults and may increase cancer death risk, according to major new research that challenges decades of medical advice.

The ASPREE Extension Study tracked 19,114 Australian and American adults over 70 for a median of 8.6 years. Researchers found no reduction in overall cancer rates among those taking daily low-dose aspirin. More concerning, the aspirin group showed increased cancer-related deaths.

“From these findings, commencing a program of low-dose aspirin for a number of years for the prevention of cancer is not recommended in older adults,” said Associate Professor Suzanne Orchard, the study director.

A separate March 2026 Cochrane review analyzing 10 randomized trials with 124,837 participants reached similar conclusions. The review found aspirin likely does not lower bowel cancer risk during the first 5 to 15 years of use.

The findings support the U.S. Preventive Services Task Force’s 2022 decision to eliminate colorectal cancer prevention from aspirin recommendations. The task force cited insufficient evidence and serious bleeding risks.

Aspirin increases major gastrointestinal bleeding risk by 58% and hemorrhagic stroke risk by 27% in cardiovascular prevention studies. The rate of major bleeding reached 8.6 events per 1000 person-years in aspirin users compared to 6.2 events in non-users.

“Age of aspirin initiation seems to play a role and younger patients may benefit more,” said Dr. Katherine Van Loon of UC San Francisco. “For now, we shouldn’t initiate aspirin therapy in an older adult for the sole purpose of cancer prevention.”

The body’s aging immune system may explain why aspirin loses effectiveness over time. Age-related immune decline and chronic inflammation may reduce aspirin’s anti-cancer effects in older people, researchers suggest.

Some studies still show long-term benefits. Adults using aspirin for more than 10 years showed reduced risks for lung cancer by 44%, breast cancer by 66%, and colorectal cancer by 63%. But these benefits take over a decade to appear.

Current guidelines recommend aspirin only for adults aged 40-59 with high cardiovascular risk and low bleeding risk. Only 10% of Americans in this age group qualify under current criteria.

“Patients will need an individualized assessment of risks and benefits,” Van Loon said. People already taking aspirin for heart conditions should consult their doctors before stopping.

Read more: Taking A Daily Aspirin For Cancer Prevention? Not So Fast