Taking a low dose of aspirin every day doesn’t prevent the most common type of stroke among older people who have never had such an event, and may raise their risk of a dangerous brain bleed.
“This is just more evidence that prescribing aspirin to people who don’t need it is not a great idea,” says John McNeil at Monash University in Melbourne, Australia.
As people age, they have an increasing chance of developing blood clots, which could block blood flow to the brain and trigger what is known as an ischaemic stroke. Attempting to counter that risk, doctors sometimes prescribe older people 75 to 100 milligrams of aspirin – generally considered to be a low dose – to take every day, as the drug thins the blood.
But aspirin, even at low doses, doesn’t come without risks, says McNeil. Last November, he and his colleagues showed that a daily low dose of aspirin increases the risks of falls in older people.
As part of the same trial, McNeil and his team investigated the incidence of strokes and internal head bleeds in 19,114 people over an average of nearly five years. Of these participants, 17,725 were at least 70 years old and living in Australia, and the vast majority of these people were white. The remaining 1389 participants were Hispanic or African American adults aged 65 and older, living in the US. None of the participants had a history of a stroke or any other cardiovascular condition at the start of the study.
Roughly half of the participants were assigned to take 100 milligrams of aspirin every day, while the other half took a placebo pill.
Among those taking low-dose aspirin, 1.5 per cent experienced an ischaemic stroke during the study period, compared with 1.7 per cent in the placebo group. Taking into consideration the number of years each person was involved in the study, the researchers found aspirin didn’t reduce their risk of an ischaemic stroke. This remained true when they broke down the categories of participants according to their age, sex and race or ethnicity.
When it comes to aspirin’s side effects, 1.1 per cent of the participants who took it experienced bleeding inside or around their brain, compared with only 0.8 per cent of those taking a placebo. While this may sound like a small difference, a statistical analysis suggests it wasn’t a chance finding. These bleeds sometimes occurred following a blow to the head, such as during a fall, but were sometimes spontaneous.
This finding is especially important because intracranial bleeding is usually more fatal than an ischaemic stroke, says McNeil. As well as aspirin’s blood-thinning properties, people’s blood vessels naturally weaken with age, making them more likely to cause a haemorrhage, he says.
The results only apply to people with no history of a cardiovascular condition, however. Low-dose aspirin may help to cut the risk of strokes in people with these conditions, says McNeil.
You should always consult your doctor before taking or changing medications.