Fourteen out of every 1,000 Covid-19 patients admitted to hospital have a stroke, a study suggests.
A team of researchers from Cambridge University’s Stroke Research Group analysed 61 published studies that covered more than 100,000 patients who had been admitted to hospital with the virus.
The rate of Covid-19 patients experiencing a stroke is higher in older people, according to the analysis published in the International Journal of Stroke.
It is also higher in those with severe infection and pre-existing vascular conditions, the research suggested.
Scientists have considered whether Covid-19 increases the risk of stroke or whether the association is a result of the virus being widespread in those who are already more likely to have a stroke.
The study’s first author Dr Stefania Nannoni, from the department of clinical neurosciences at the University of Cambridge, said: “The picture is complicated.
“For example, a number of Covid-19 patients are already likely to be at increased risk of stroke.
“And other factors such as the mental stress of Covid-19 may contribute to stroke risk.
“On the other hand, we see evidence that Covid-19 may trigger – or at least be a risk factor for – stroke, in some cases.
“Firstly, SARS-CoV2 more so than other coronaviruses – and significantly more so than seasonal flu – appears to be associated with stroke.
“Secondly, we see a particular pattern of stroke in individuals with Covid-19, which suggests a causal relationship in at least a proportion of patients.”
Just over 12 out of every 1,000 Covid-19 patients who were admitted to hospital suffered an acute ischemic stroke, where the blood supply is stopped because of a clot, according to the research.
Brain haemorrhage was less common, occurring in 1.6 out of every 1,000 cases.
Most of these patients had been admitted with Covid-19 symptoms and suffered strokes a few days later.
“Given that patients admitted to hospital with symptoms of stroke might have mild Covid-19-related respiratory symptoms, or be completely asymptomatic, we recommend that all patients admitted with stroke be treated as potential Covid-19 cases until the results of screening in the hospital are negative,” said Dr Nannoni.
Covid-19 patients who experienced a stroke were 4.8 years older than those who did not, on average.
They were, on average, six years younger than non-Covid-19 stroke patients.
Unsurprisingly, pre-existing conditions also increased the risk of stroke.
Patients with high blood pressure were more likely to experience stroke than patients with normal blood pressure, while both diabetes and coronary artery disease also increased risk.
Patients who had a more severe infection were also more likely to have a stroke.
Covid-19-associated strokes were also more severe and had a high mortality.
There was no significant difference seen between smokers and non-smokers, nor was one seen between the sexes.
Researchers say there may be several possible mechanisms behind the link between Covid-19 and stroke.
Professor Hugh Markus, who leads the Stroke Research Group at Cambridge, said: “Even though the incidence of stroke among Covid-19 patients is relatively low, the scale of the pandemic means that many thousands of people could potentially be affected worldwide.
“Clinicians will need to look out for signs and symptoms of stroke, particularly among those groups who are at particular risk, while bearing in mind that the profile of an at-risk patient is younger than might be expected.”