This article explores recent research on daily low-dose aspirin (100 mg) for preventing cancer and other chronic diseases in older adults. The key findings come from the large ASPREE trial involving 19,114 healthy participants aged 70+ (or 65+ for minorities). Surprisingly, aspirin showed no benefit for preventing dementia or physical disability, and was linked to a 14% increase in overall deaths—primarily due to cancer. These results contradict earlier studies showing aspirin's protective effects against colorectal cancer in younger adults. Patients should discuss personalized aspirin use with their doctors.

Understanding Aspirin for Cancer Prevention in Older Adults: New Research Insights

Table of Contents

• Introduction: Why This Research Matters
• How the Study Was Conducted
• Key Findings: What the ASPREE Trial Revealed
• Why Might Aspirin Have Different Effects in Older Adults?
• What This Means for Patients
• Study Limitations
• Recommendations for Patients
• Source Information

Introduction: Why This Research Matters

In 2016, health experts recommended low-dose aspirin (81 mg daily) for adults aged 50-59 to prevent heart disease and colorectal cancer. This was based on strong evidence showing aspirin reduced colorectal cancer risk by 24% in multiple studies. However, there wasn't enough data for adults over 70. The ASPREE trial was launched specifically to fill this gap.

Researchers wanted to understand if aspirin's potential benefits for preventing dementia, disability, and cancer in healthy older adults outweighed its known bleeding risks. This question is critical because cancer risk increases with age, and safe prevention strategies are urgently needed. The trial's results challenge previous assumptions and have major implications for millions of older adults considering aspirin.

How the Study Was Conducted

The ASPREE trial followed rigorous scientific standards. Researchers enrolled 19,114 healthy participants: 16,703 from Australia and 2,411 from the U.S. All were aged 70+ (or 65+ for racial/ethnic minorities), with 56% women and 9% minorities. About 11% had previously used aspirin regularly.

Participants were randomly assigned to one of two groups:

• Group 1 took 100 mg of enteric-coated aspirin daily
• Group 2 took a placebo (inactive pill)

Neither participants nor researchers knew who received which treatment. The study tracked participants for an average of 4.7 years through annual checkups. The main goal was to see whether aspirin improved "disability-free survival"—meaning avoidance of dementia, physical disability, or death. Importantly, the trial was stopped early in June 2017 when initial data showed low likelihood of benefit.

Key Findings: What the ASPREE Trial Revealed

The results, published in 2018, were unexpected:

• No primary benefit: Disability-free survival occurred in 21.5 per 1,000 person-years in the aspirin group versus 21.2 in the placebo group. The difference was not statistically significant (Hazard Ratio [HR] 1.01; 95% Confidence Interval [CI] 0.92–1.11; P=0.79).
• Increased mortality: All-cause death rates were 14% higher in the aspirin group (HR 1.14; 95% CI 1.01–1.29). This equated to about 5 extra deaths per year per 1,000 people.
• Cancer drove the risk: Cancer deaths increased by 31% (HR 1.31; 95% CI 1.10–1.56), affecting colorectal, breast, lung, stomach, and esophageal cancers. Notably, cancer incidence itself didn't significantly differ (981 cancers with aspirin vs. 952 with placebo).

The increased death risk was most pronounced in those without prior aspirin use and among Australian participants. In contrast, U.S. participants and prior aspirin users showed non-significant risk reductions (HR 0.79 and HR 0.86 respectively).

Why Might Aspirin Have Different Effects in Older Adults?

Researchers proposed five hypotheses to explain why aspirin increased cancer deaths in older adults while showing protection in younger populations:

1. Timing hypothesis: Aspirin may prevent tumor formation in younger adults but accelerate growth in existing, undiagnosed cancers common in the elderly.
2. Age-related biology: Cancers in older adults may develop through different biological pathways less responsive to aspirin's anti-inflammatory effects.
3. Trial design effects: Stopping aspirin when cancer was diagnosed might cause a harmful "rebound" effect not seen in real-world settings.
4. Chance finding: The mortality increase was a secondary outcome and could be a statistical fluke (though unlikely).
5. Prior studies were flawed: This contradicts consistent evidence from trials like the Women's Health Study showing 20% lower colorectal cancer risk.

Table 1 summarizes key trials comparing aspirin's effects:

What This Means for Patients

These findings have immediate practical implications:

• For adults over 70: Aspirin should not be started solely for cancer or heart disease prevention. The risks outweigh benefits in healthy older adults.
• For adults 50-59: Existing recommendations supporting aspirin for those with ≥10% cardiovascular risk remain valid.
• For current aspirin users: Do NOT stop aspirin without consulting your doctor. ASPREE found higher risks primarily in new users—those already taking aspirin had non-significant risk reductions.

The decision to continue aspirin should be personalized, weighing your cardiovascular risk, cancer history, and bleeding susceptibility.

Study Limitations

While ASPREE was well-designed, important limitations exist:

• The 4.7-year follow-up might be too short to detect long-term benefits (prior trials showed cancer protection only after 5+ years).
• Cancer mortality was a secondary outcome—results need confirmation.
• Only 66% of death records were available for detailed analysis.
• The study didn't exclude people with undiagnosed cancers, which may have influenced results.

Ongoing follow-up of ASPREE participants may provide clearer answers about long-term effects.

Recommendations for Patients

Based on current evidence:

1. If you're under 60 with high cardiovascular risk: Discuss aspirin with your doctor—benefits may outweigh risks.
2. If you're over 70 and healthy: Avoid starting aspirin for prevention.
3. If you already take aspirin: Consult your doctor before making changes—do NOT stop abruptly.
4. Focus on proven strategies: Prioritize colorectal cancer screening (colonoscopy), exercise, and smoking cessation over aspirin for cancer prevention in later life.

Future research may identify specific groups who still benefit from aspirin, such as those with certain genetic markers.

Source Information

Original article title: Aspirin and Cancer Prevention in the Elderly: Where Do We Go From Here?
Authors: Andrew T. Chan, John McNeil
Publication: Gastroenterology, Volume 156, Issue 3, February 2019, Pages 534-538
Note: This patient-friendly article is based on peer-reviewed research.