Thursday May 19 2016
Aspirin can help dissolve blood clots
"People should consider taking aspirin immediately after a minor stroke," BBC News reports.
A review of existing evidence found people treated with aspirin after a mini stroke (transient ischaemic attack, or TIA) were less likely to experience a more serious follow-up stroke.
A TIA occurs when a blood clot temporarily blocks blood flow in the brain. It causes problems including numbness or weakness of the face, arms or legs, as well as dizziness and problems with speech and sight.
These usually pass quickly, but are a warning sign of the possibility of a second, more serious stroke in the next few weeks. If you have these symptoms or see someone with them, you should call 999 for an ambulance immediately.
The review found taking aspirin reduced the risk of having another stroke by about 60% in the first six weeks, and of having a disabling or fatal stroke by 70%.
The researchers also suggest people who have symptoms of a stroke should be advised to take aspirin straight away, while waiting for medical help.
But the possible risk of doing this is that if stroke symptoms are caused by bleeding inside the brain, taking an aspirin could make the situation much worse.
The transient symptoms of a TIA are most likely to be caused by a clot, but still, the advice on self-treatment needs to be considered by experts before we can recommend it. The key point is to get medical help immediately by dialling 999.
Where did the story come from?
The study was carried out by researchers from the University of Oxford, University Medical Centre Utrecht, University Duisburg-Essen and Lund University.
It was funded by the Wellcome Foundation and the National Institute of Health Research Biomedical Research Centre.
The study was published in the peer-reviewed journal The Lancet on an open access basis, meaning it's free to read online.
On the whole, UK media coverage was good, with accurate reporting of the research and the researcher's conclusions.
What kind of research was this?
This was a meta-analysis of randomised controlled trials (RCTs), in which researchers pooled data from a number of studies to get the best summary of the results.
This analysis looked specifically at the effects of the treatment (aspirin) over the course of time.
The researchers wanted to see the effects of aspirin at particular times after a stroke – either a transient ischaemic attack (TIA) or a full stroke caused by a blood clot (ischaemic stroke).
While meta-analyses can provide reliable results, they are only as good as the studies they contain, and there may have been variability in the study design and assessments.
What did the research involve?
Researchers analysed all RCTs that measured the effects of aspirin given after an ischaemic stroke or TIA to prevent a future stroke.
Because many of these trials did not start treatment straight away, they also looked at trials where aspirin was given to people being treated within 48 hours of having a stroke.
They measured the effects of aspirin on repeated stroke and the severity of repeat strokes at up to six weeks after the stroke, between 6 and 12 weeks, and more than 12 weeks.
Most of the studies that established the place of aspirin in the treatment and prevention of stroke were done in the 1980s and 1990s, so some of this research is quite old.
The researchers pooled individual patient data from the studies and stratified it into time periods.
They also looked at studies including the anti-clotting drug dipyramidole, which is sometimes used alongside or instead of aspirin, to see what effect the two drugs had at different time points.
The researchers also assessed the effects of the severity of the first stroke on the results.
What were the basic results?
The risk of having a repeat stroke within six weeks of the initial TIA was cut by about 60% for people taking aspirin.
Just under 1% of people who took aspirin had a repeat stroke within six weeks, compared with 2.3% of people who did not take aspirin (hazard ratio [HR] 0.42, 95% confidence interval [CI] 0.32 to 0.55).
The risk of having a disabling or fatal stroke was cut even more, by about 70% (HR 0.26, 95% CI 0.2 to 0.42). People who'd had a TIA or minor stroke were more likely to benefit from aspirin treatment than those who'd had more severe strokes.
The risk of having a second stroke between 6 and 12 weeks later was also reduced for people taking aspirin.
But after 12 weeks, people who'd taken aspirin were as likely to have a stroke as those who hadn't taken aspirin.
This suggests the effects of aspirin are most important in the weeks immediately after a stroke or TIA, when the risk of another stroke is highest.
When the researchers looked at patients who'd been treated with aspirin immediately after an acute stroke, they again saw a drop in the risk of a repeat stroke, and found this drop in risk was biggest for patients who'd had less severe strokes.
In the trials that compared aspirin with dipyramidole, aspirin alone worked as well as aspirin with dipyramidole to reduce stroke risk in the first 12 weeks, but dipyramidole worked better after 12 weeks.
How did the researchers interpret the results?
The researchers said their results show that the effects of aspirin in reducing the risk of stroke immediately after a first stroke or TIA have been underestimated.
They said that, "It is essential that aspirin is given to patients with suspected TIA or minor stroke immediately."
They went on to suggest that, "Consideration should be given to promoting self-administration [i.e. taking aspirin yourself] immediately after transient stroke-like neurological symptoms."
They also said it would be "prudent" to run a public education campaign to encourage people to seek medical help immediately after having symptoms of stroke, and also to take aspirin.
The study supports current recommended practice that people with a TIA or ischaemic stroke caused by a blood clot are treated with aspirin as soon as possible.
NHS experts are considering whether to recommend that you take aspirin yourself while waiting for medical help.
The reason this isn't recommended at present is that some people will have had a haemorrhagic (bleeding) stroke, and aspirin can make the bleeding worse.
For people who've had a full stroke, an urgent brain scan is usually performed to exclude bleeding as a cause and check it's safe to proceed with anti-clotting treatment. The risk of transient symptoms being caused by bleeding is much smaller, but it is possible.
Until official guidelines are produced – NHS England are reportedly considering the report's findings – current advice still stands. If you are experiencing the symptoms of a stroke, the most important thing is to call for an ambulance immediately.
The new study included thousands of people from high-quality RCTs, so the results are likely to be reliable, although there are some limitations.
Most of the studies included were conducted 20 or 30 years ago, and the medical treatment of stroke has improved since then, so the results might be different if the trials were run again now.
People who have had a stroke nowadays are more likely to be treated urgently, although too many people with minor strokes or TIAs don't seek help quickly enough.
This analysis would be stronger if the studies included had more people randomised to aspirin treatment within hours or days of their stroke or mini stroke.
However, this would be likely only to strengthen the effects seen with aspirin, and it's unlikely that trials involving more people treated quickly would undermine the main results.
The key point is not to ignore the symptoms of a stroke or TIA, but to treat it as a medical emergency, as you would do a heart attack, and call 999 for help.