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Aspirin: the preventative that wasn’t

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For most doctors, preventative medicine means giving patients drugs. The drugs may be different from the ones they’d prescribe when the patient gets sick, but they’re drugs nonetheless. And sitting at the very apex of preventative drugs is aspirin, with doctors telling patients over the age of 50 that they should start taking 75 mg a day to prevent heart disease and stroke. More recently, they’ve added colorectal (bowel) cancer to the list.

And it does seem to be doctors – and patients who are self-medicating – who are driving this and even going against the advice of health agencies. For one, the US Food and Drug Administration (FDA) has stated that it “does not believe the evidence supports the general use of aspirin for primary prevention of a heart attack or stroke.”

One survey highlighting the problem found that almost half of respondents with no history of heart disease were taking aspirin, which is contrary to the recommendations of agencies such as the FDA. And the strongest predictor of taking aspirin – whether correctly or incorrectly – was having discussed it with their doctor.1

But then doctors are getting mixed messages. Thousands of headline-grabbing medical trials (around 3,500 are published every year) have claimed that aspirin is a lifesaver – both against heart disease and stroke, and now colorectal cancer – while groups such as the American Heart Association support the use of low-dose aspirin to protect against heart disease, especially in women under 65; the UK’s National Health Service (NHS) website also recommends low-dose aspirin as a preventative drug.

And what’s not to like about aspirin? Used as a painkiller, fever reducer and anti-inflammatory for the better part of a century, it’s seen as a benign remedy that we’ve taken for years for aches and pains, and now to prevent heart disease. As a result, we pop around 100 billion aspirin pills every year worldwide, many taken by healthy people who agree with their doctor that aspirin is, indeed, the ultimate just-in-case remedy.

The statistics seem to back up the claim that it’s a safe drug. The American Association of Poison Control Centers reports an average of 59 deaths from aspirin a year, while researchers have estimated that just 7,600 people die each year from complications of taking an NSAID (nonsteroidal anti-inflammatory drug) painkiller, whether it’s aspirin, ibuprofen or naproxen.2

Yet, even in the early days when aspirin was first being promoted as a heart disease preventative, there were those who questioned its benefits and safety. Lately, those voices have reached a crescendo. They warn that aspirin isn’t as effective as claimed, and it’s not so benign either.

Not for those over 70

Researchers from Monash University in Australia think that any healthy person over the age of 70 should stop taking aspirin. Once you reach that age – and provided you don’t have any heart problems – the risks of taking aspirin start outweighing the benefits. In fact, that threshold could be reached as early as age 45, say the researchers, who looked at the effects of aspirin on a group of 19,114 healthy people, half of whom were taking 100 grams of aspirin a day and the rest a placebo, or dummy pill. For a healthy 45-year-old, the way to prevent heart disease is through diet and exercise, not by turning to aspirin.

When the researchers analyzed the two groups – those taking an aspirin a day and those taking a placebo – they discovered that there was no difference in the number of heart disease cases after seven years. However, the rate of life-threatening hemorrhages, including bleeding in the stomach and brain, was much higher in the aspirin group.3

Researchers from Brigham and Women’s Hospital in Boston came to a similar conclusion when they took a look at the effects of aspirin on a group of people who were at moderate risk of having a first heart attack, based on their high blood pressure or cholesterol levels. Half of the 12,546 people in the study were taking aspirin, and the rest – with a similar risk profile – were instead given a placebo.

In the five years of the study, heart attack rates were similar in both groups; in other words, aspirin wasn’t protective. Yet many more in the aspirin group also suffered gastrointestinal (GI) bleeding.4

GI blues

Although GI bleeding is a recognized side-effect of taking aspirin, the risk is far greater than many believe, and it becomes life-threatening by the time you reach the age of 75. By then, your risk of a major stomach bleed is four times greater than in younger age groups.

Among people under 65 taking aspirin, the rate of fatal or life-threatening bleeds was less than 0.5 percent, or one person out of every 200. But the rate rises to over 1.5 percent – three people per 200 – among those over 75, and the risk continues to grow the older people get, researchers from Oxford University have discovered.

The researchers tracked the health of 3,166 people, half of whom were 75 or older, who were prescribed aspirin after a heart attack or stroke to prevent them from having another one. In total, 405 of them suffered a serious bleeding event – mainly in the stomach, but also in the brain or elsewhere in the body. This was three times more likely to happen in those who were 75 or older.

People over 75 should either take another drug – known as a proton pump inhibitor (PPI) – if they are going to continue taking aspirin, the researchers concluded, or they should come off the aspirin gradually, since the risk of a fatal bleed outweighs any benefit in preventing a second heart attack or stroke.5

In fact, people who have already suffered a heart attack might not see much benefit from aspirin anyway, researchers from the University of Florida have found. And people suffering from atherosclerosis – hardening or narrowing of the arteries – aren’t helped at all by taking the painkiller.

The researchers tracked the health of around 33,000 people with atherosclerosis and discovered that among those who had already had a heart attack, taking aspirin appeared to lead to a “marginally lower risk” of having a second one. But for those who had never suffered a heart attack or stroke, taking aspirin didn’t have any protective effect: the risk was 10.7 percent among those who took aspirin and 10.5 percent in those who didn’t.

The only people who actually seemed to be helped by taking aspirin were the subset of patients with a history of coronary bypass surgery or stent placement to widen an artery but no prior heart attack or stroke.6

< span style="color:#008000;">Here’s the resistance

It gets worse. Far from protecting them against cardiovascular disease, aspirin could be doing nothing for the people who need its blood-thinning effects the most. They have a biological resistance to the drug that also dramatically increases their risk of a heart attack.

One study has estimated that 41 percent of aspirin-resistant people with heart disease will suffer a heart attack, and for 6 percent of these, it will be fatal. But even if aspirin doesn’t have the desired effect in these cases, it still comes with all the same risks – meaning that around 65 million Americans and 16 million Britons shouldn’t be taking it.7

Even those of us who aren’t resistant should think twice. For one, the rate of GI bleeding that aspirin causes could be far greater than current estimates predict – and it could be double what has been cited, even at low doses. People taking aspirin are almost twice as likely as non-users to suffer a GI bleed, one study of 66,000 patients discovered.8

And this could be because many cases go under the radar, and aspirin is never suspected as being the culprit. Researchers from Eastern Virginia Medical School interviewed patients being treated for GI problems and found that only 20 percent had even bothered to tell their doctors they were taking aspirin or another over-the-counter NSAID.

Putting aspirin back into the frame, the researchers estimate NSAIDs like aspirin are killing 20,000 Americans a year (slightly more than the 59 actually recorded in the US each year). Globally, the drugs could be responsible for 100,000 deaths and 500,000 emergency hospital treatments every year.9

What’s the upside?

The studies that are most favorable to preventative aspirin suggest that taking one a day for 10 years could reduce your risk of a major cardiovascular event, such as a heart attack or stroke, by around 10 percent, and your risk of coronary artery disease by 15 percent. This translates into 33 to 44 fewer deaths for every 100,000 people taking the drug.

A similar picture emerges for colon cancer. For every 100,000 people taking an aspirin a day for five years, there would be 34 fewer deaths from this disease, on average.

But . . . factor in the real risks of aspirin, with 100,000 deaths globally each year from GI bleeding, and the risk-reward ratio becomes a very fine balance.

And compare that to the simple fact that 68,000 cancer cases a year could be prevented in the US alone if people started taking a multivitamin supplement every day. 1

It’s a no-no for those over 75

By the time you reach the age of 70 – and certainly when you hit your 75th birthday – aspirin should be off the table. By then, your arteries will probably not be as strong as they were, which makes you more liable to internal bleeding, and aspirin increases the risk further.

A 75-year-old’s chances of intracerebral hemorrhagic stroke (or bleeding in the brain) is seven times higher now than it was in the 1980s – and Professor Peter Rothwell of Oxford University suspects aspirin could be playing some part in that enormous increase.

As he points out, the risk starts on the first day you take aspirin, and yet any protective effects won’t be apparent for 10 years or so.

Although it’s hard to provide absolute proof that aspirin is partly to blame for the increased stroke rate, Rothwell says there’s a correlation with the increased use of NSAIDs such as aspirin; in 1984, just 4 percent of healthy people were taking aspirin, and this had risen to 40 percent by 2006.

“There are elderly people who take aspirin as a lifestyle choice, and in that situation the trials have shown there’s no benefit. And what our study suggests is that, particularly in the very elderly, the risks of aspirin outweigh the benefits,” he said.1

What’s the upside?



Postgrad Med, 2015; 127: 107-16

It’s a no-no for those over 75



Lancet Neurol, 2007; 6: 487-93

Main article



Am J Prev Med, 2015; 48: 501-8


Scand J Rheum Suppl, 1992; 92: 21-4


New Engl J Med, 2018; 379: 1509-18


Lancet, 2018; 392: 1036-46


Lancet, 2017; 390: 490-9


Clin Cardiol, 2017; 40: 732-9


Daily Telegraph, Dec 3, 2015


BMJ, 2000; 321: 1183-7


Gastroenterology Insights, 2013; 5: e3

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