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December 1 2016
You shouldn’t take daily aspirin unless a doctor advises you to.
Aspirin can help prevent blood clots.
"Aspirin a day could dramatically cut cancer and heart disease risk … study claims," the Mail Online reports.
U.S. researchers ran a simulation of what might happen if all Americans over 50 years old took aspirin on a daily basis. Their results found that people would live about four months longer on average, adding 900,000 people to the US population by 2036.
More info from NHS.uk.
The study was designed to demonstrate the possible long-term effects of more people taking aspirin to prevent cardiovascular disease.
It should be pointed out that there is an important difference between UK and US guidelines. In the UK low-dose aspirin is usually recommended for people with a history of heart disease or stroke. In the US this advice is extended to people who are at risk of cardiovascular disease but don't have it yet.
We already know that aspirin reduces the risk of heart disease and strokes caused by blood clots (ischaemic stroke). There's some evidence it may reduce some types of cancer. However, aspirin also increases the risk of stroke caused by bleeding (haemorrhagic stroke) and increases the chances of bleeding in the stomach or gut.
So should you be taking low-dose aspirin? Without knowing your individual circumstances it is impossible to provide an accurate response. You need to ask your GP.
Where did the story come from?
The study was carried out by researchers from the University of Southern California and a company called Analysis Group. The authors received no funding for the study.
The study was published in the peer-reviewed journal PLOS One, on an open-access basis so it's free to read online.
The Mail Online reports the study as if the findings about aspirin reducing cardiovascular disease and potentially extending lifespan were new, while they have actually been known for some time.
The report says taking aspirin "would save the US $692 billion in health costs," which seems to be a misunderstanding. Health costs would actually increase, because of people living longer.
However, the researchers assigned a value of $150,000 to each additional year of life lived, which is how they arrived at the $692 billion figure.
What kind of research was this?
This was a "microsimulation" study, which used a modelling system to project possible outcomes under different scenarios, using information from health surveys. This type of modelling can throw up some interesting possibilities, but because it relies on so many assumptions, we have to be cautious about taking the results too literally.
What did the research involve?
Researchers used data from cohort studies to predict average life expectancy, cardiovascular events, cancers, disabilities and healthcare costs for people in the US aged 50 and over. They predicted what would happen with the current numbers of people taking aspirin, then with everyone currently recommended to take aspirin doing so, then with everyone over 50 taking aspirin.
They compared the results of their modelling, to see what effect it would have on average lifespan, the US population, costs and benefits.
Cohort studies providing data included the National Health and Nutrition Examination Survey (NHANES), Health and Retirement Study of Americans, Medical Expenditure Panel Survey and Medicare Current Beneficiary Survey.
The model included an assumption that more people would have gastrointestinal bleeding as a result of taking aspirin. It also modified the results using quality of life measures, so that additional life years were adjusted for quality of life.
What were the basic results?
The researchers found that, if everyone advised by US guidelines to take aspirin did so, the:
- numbers of people with cardiovascular disease would fall from 487 per 1,000 to 476 per 1,000 (11 fewer cases, 95% confidence interval (CI) -23.2 to -2)
- numbers with gastrointestinal bleeding would rise from 67 per 1,000 to 83 per 1,000 (16 more cases, 95% CI 3.6 to 30)
- years of life expectancy at age 51 would rise from 30.2 years to 30.5 years, an additional four months of life (0.28 year, 95% CI 0.08 to 0.5)
- life expectancy without disability would rise from 22.8 years to 22.9 years, an additional one month of life (0.12 year, 0.03 to 0.23)
The model found no reduction in the numbers of strokes or cancers.
The model shows there could be an additional 900,000 people (CI 300,000 to 1,400,000) alive in the US in 2036, who would otherwise have died.
Using the figure of $150,000 per quality-adjusted life year to represent benefits, the researchers say the value of extra life gained by 2036 would be $692 billion.
How did the researchers interpret the results?
The researchers said: "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."
Conclusion
This study doesn't really tell us anything we didn't already know. Aspirin has been used for many years to prevent heart attacks and strokes in people with cardiovascular disease. Aspirin's wider use is controversial, because of the potential side effects.
What this study does add is an estimate of what might happen if all people in the US who were advised to take aspirin under US guidelines, actually did so. (The researchers say that 40% of men and 10% of women advised to take aspirin don't take it).
The study assumes that people would get the same benefits as those seen in clinical trials of aspirin. This is unrealistic, because most studies find that people tend to do better in clinical trials than when being treated in the real world.
The average results – showing an additional one month of disability-free life for every 1,000 people – may sound trivial. However, it's important to remember that averages don't work like that in real life. Many people will get no benefit from aspirin, while a smaller group will avoid a heart attack or stroke, and so live many more months or possibly years, as a result of taking aspirin.
If you've already had a heart attack or stroke, or if you have angina or another heart or circulation problem, your doctor has probably prescribed low dose aspirin. There's good evidence that aspirin (or similar drugs, for those who can't take aspirin) can help prevent a second heart attack or stroke.
Find out more information about aspirin.
Analysis by Bazian. Edited by NHS Choices. Follow NHS Choices on Twitter. Join the Healthy Evidence forum.
Analysis by Bazian
Edited by NHS Choices
Links to the headlines
Aspirin a day could dramatically cut cancer and heart disease risk - and even extend lifespan, study claims. Mail Online, November 30 2016
Links to the science
Agus DB, Gaudette E, Goldman DP, Messali A. The Long-Term Benefits of Increased Aspirin Use by At-Risk Americans Aged 50 and Older. PLOS One.
Published online November 30 2016
