Wider use of low-dose aspirin by older Americans at higher risk of cardiovascular disease could be a cost-effective way to generate substantial population health benefits over the next 20 years.
So concludes a study from the University of Southern California (USC) in Los Angeles and published in the journal PLOS One.
The researchers say although the health benefits of a daily low-dose aspirin regimen are well established, few people who might benefit from it take it.
As well as being a painkiller, aspirin has anticoagulant properties that can help patients at risk of heart disease by thinning the blood and prevent it clotting.
Confusing advice about aspirin and heart disease
The researchers suggest people at risk of heart disease are likely confused about whether to take aspirin because they are hearing contradictory advice.
For example, updated guidelines from the United States Preventive Services Task Force (USPSTF), a government-backed panel of experts, recommend daily low-dose aspirin for the prevention of a first heart attack (so-called primary prevention) among at-risk older Americans who meet certain criteria.
More specifically, the USPSTF guidelines recommending low-dose daily aspirin for the primary prevention of cardiovascular disease and colorectal cancer in older adults differ slightly, depending on age group. (Note that as well as heart attacks, cardiovascular disease includes other types of heart and circulation conditions, such as stroke and angina.)
For those aged 50-59 years, the recommendation applies to those who meet the following criteria: have a 10 percent or higher risk of developing cardiovascular disease in next 10 years; do not have raised risk for bleeding; have a life expectancy of at least another 10 years; and are willing to take low-dose aspirin every day for at least the next 10 years.
For those aged 60-69 years who have a 10 percent or higher risk of developing cardiovascular disease, the decision should be an individual one, say the USPSTF guidelines. Those in this group who are not at increased risk for bleeding, have a life expectancy of at least another 10 years, and are willing to take low-dose aspirin every day for at least 10 years are the most likely to benefit.
The Food and Drug Administration (FDA), on the other hand, are not in favor of low-dose aspirin for primary prevention of a heart attack or stroke.
The FDA say there are certain primary prevention situations where the risk of bleeding in the stomach and brain from use of aspirin outweighs the benefits. However, this is not their view for preventing a second heart attack or stroke, where they note "patients who have had such cardiovascular events, the known benefits of aspirin for secondary prevention outweigh the risk of bleeding."
Étienne Gaudette, co-author of the new study and an assistant professor in the USC school of pharmacy, says:
"The problem that this creates for Americans and medical professionals is that the information about aspirin is confusing."
Future Elderly Model
For their study, the researchers assessed the long-term benefits of low-dose aspirin use with the help of a USC mathematical model called the Future Elderly Model. This takes data from large surveys and predicts the health of older Americans as they age.
The model relies on three national data sets: the U.S. Health and Retirement Study of Americans 51 and older, the large-scale Medical Expenditure Panel Survey of non-institutionalized Americans, and the Medicare Current Beneficiary Survey. The researchers also added data from the National Health and Nutrition Examination Survey.
The model takes into account a range of variables, such as chronic disease, ability to carry out everyday tasks, body mass index (BMI), and rates of death.
The researchers used the model to assess two scenarios: Guideline Adherence, and Universal Eligibility. In the Guideline Adherence scenario, the model assesses the health and financial pros and cons that would result if Americans who met the USPSTF criteria had started following the guidelines from 2009.
In the Universal Eligibility scenario the model does a similar assessment but assumes all Americans aged 51 and over - whether they meet the criteria or not - take low-dose aspirin every day and benefit from it.
The results show that following the guidelines (the adherence scenario) would prevent 11 cases of heart disease and four cases of cancer for every 1,000 Americans aged 51-79. This would also improve life expectancy by 0.3 years - in other words, out of every 1,000 people, eight more would see their 80th birthday and three more their 100th. Also, this additional lifespan would be largely free of disability.
The model also estimates that following the daily aspirin guidelines would mean 900,000 more Americans would be alive in 2036 and the U.S. could expect to see $692 billion in net health benefits over that period.
The authors note that the results "reveal a large unmet need for daily aspirin, with over 40 percent of men and 10 percent of women aged 50 to 79 presenting high cardiovascular risk but not taking aspirin."
Drawbacks and limitations
On the downside, the model shows no significant reduction in rates of stroke. Also, the rate of stomach bleeding would rise 25 percent above the current rate, meaning 2 out of 63 people on the low-dose aspirin regimen would likely suffer a bleed between the ages 51-79.
The scenario where every American over 50 takes aspirin showed only slightly larger health benefits.
The authors point out that while people living longer usually means higher medical costs, in this case, "observing the guidelines would yield positive and significant net value."
They also suggest the study has some possible limitations. For instance, the model assumes the benefits of aspirin use can be generalized to everyone taking it, which is unlikely to be the case in the real world.
Another limitation could be that taking aspirin could reduce people's incentive to do other things that reduce risk, like changing their diet and being more physically active.
"Risk prevention for the elderly is critical to achieving the health benefits required for optimal long-term economic and population health. Expanded use of aspirin by older Americans with elevated risk of cardiovascular disease could generate substantial population health benefits over the next twenty years and do so very cost-effectively."
David B. Agus et al.