Millions of seniors take a low-dose daily aspirin in hopes of preventing blood clots that can cause strokes and heart attacks. But a large clinical trial finds little benefit for those who have not had previous cardiovascular issues.
The results of the study, which began in 2010, showed that aspirin did not extend healthy independent living, defined as life free of dementia or persistent physical disability. Risk of dying from a range of causes, including cancer and heart disease, varied and will require further analysis and additional follow-up, the researchers said.
“The results will have a significant impact on guidelines about aspirin use for prevention and in daily clinical conversations between clinicians and their older, healthy patients regarding whether aspirin should or should not be used for achieving disability-free longevity,” said Dr. Raj C. Shah, an associate professor of family medicine with the Rush Alzheimer’s Disease Center in Chicago.
The trial enrolled 19,114 older people in Australia and the United States. Study participants were enrolled at 70 years of age or older, with 65 as the minimum age of entry for African-American and Hispanic individuals in the United States because of their higher risk for dementia and cardiovascular disease. They were followed for an average of 4.7 years to determine outcomes. The study appears in the New England Journal of Medicine.
Higher death rate
In the total study population, treatment with 100 mg of low-dose aspirin per day did not affect survival free of dementia or disability. Among the people randomly assigned to take aspirin, 90.3 percent remained alive at the end of the treatment without persistent physical disability or dementia, compared with 90.5 percent of those taking a placebo. Rates of physical disability were similar, and rates of dementia were almost identical in both groups.
The group taking aspirin had an increased risk of death compared to the placebo group: 5.9 percent of participants taking aspirin and 5.2 percent taking placebo died during the study. This effect of aspirin has not been noted in previous studies, and caution is needed in interpreting this finding, the researchers cautioned.
The higher death rate in the aspirin-treated group was due primarily to a higher rate of cancer deaths. A small increase in new cancer cases was reported in the group taking aspirin, but the difference could have been due to chance.
Bleeding and cancer risks
Researchers found little difference in heart attack and stroke. They found that the rates for major cardiovascular events — including coronary heart disease, nonfatal heart attacks, and fatal and nonfatal ischemic stroke — were similar in the aspirin and the placebo groups. In the aspirin group, 448 people experienced cardiovascular events, compared with 474 people in the comparably-sized placebo group.
Significant bleeding — a known risk of regular aspirin use — also was measured. The investigators noted that aspirin was associated with a significantly increased risk of bleeding, primarily in the gastrointestinal tract and brain. Clinically significant bleeding — hemorrhagic stroke, bleeding in the brain, gastrointestinal hemorrhages or hemorrhages at other sites that required transfusion or hospitalization — occurred in 361 people (3.8 percent) on aspirin and in 265 (2.7 percent) taking the placebo.
As would be expected in an older adult population, cancer was a common cause of death, and 50 percent of the people who died in the trial had some type of cancer. Heart disease and stroke accounted for 19 percent of the deaths, and major bleeding for 5 percent.
It’s not the first study to cast doubt on the widely accepted theory that a daily aspirin may be beneficial.
In 2017, researchers in Salt Lake City found that using long-term aspirin therapy to prevent strokes among patients who are considered to be at low risk for stroke may not be effective as previously thought. The study found that atrial fibrillation patients who received a catheter ablation and were low risk of stroke didn’t benefit from long-term aspirin therapy, but were at risk of higher rates of bleeding compared to no therapy at all.
“This study continues to show that aspirin has little to no benefit for stroke prevention in AF (atrial fibrillation) patients and when used in low-risk patients it significantly increases a patient’s bleeding risk,” said Jared Bunch, MD, the study’s lead author and director of Heart Rhythm Research at the Intermountain Medical Center Heart Institute.
A Florida study released in 2017 found that aspirin may have little or no benefit for patients who have plaque buildup but have not had a heart attack or stroke.
University of Florida researchers tracked the health histories of over 33,000 patients with atherosclerosis — narrowed, hardened arteries — and determined that aspirin is marginally beneficial for those who have had a previous heart attack, stroke or other blood-flow issues involving arteries. However, among atherosclerosis patients with no prior heart attack or stroke, aspirin had no apparent benefit. The findings were published in the journal Clinical Cardiology.
Findings don’t apply to patients with cardiovascular conditions
The researchers emphasized that the study’s findings do not apply to patients with known cardiovascular conditions — since the participants in the study were healthy. They also emphasized that consumers should discuss the study with their physician before making any changes in their daily routine.
Dr. Evan Hadley, director of the National Institute on Aging’s Division of Geriatrics and Clinical Gerontology emphasized that older adults should follow the advice from their own physicians about daily aspirin use. It is important to note that the new findings do not apply to people with a proven indication for aspirin such as stroke, heart attack or other cardiovascular disease.
In addition, the study did not address aspirin’s effects in people younger than age 65. Also, since only 11 percent of participants had regularly taken low-dose aspirin prior to entering the study, the findings need further investigation to determine whether healthy older people who have been regularly using aspirin for disease prevention should continue or discontinue use.
“Clinical guidelines note the benefits of aspirin for preventing heart attacks and strokes in persons with vascular conditions such as coronary artery disease,” said NIA Director Dr. Richard J. Hodes. “The concern has been uncertainty about whether aspirin is beneficial for otherwise healthy older people without those conditions. This study shows why it is so important to conduct this type of research, so that we can gain a fuller picture of aspirin’s benefits and risks among healthy older persons.”