Risk of blood clots remains for almost a year after COVID-19 infection, study suggests
Press release issued: 20 September 2022
COVID-19 infection increases the risk of potentially life-threatening blood clots for at least 49 weeks, according to a new study of health records of 48 million unvaccinated adults from the first wave of the pandemic.
The findings suggest that the COVID-19 pandemic may have led to an additional 10,500 cases of heart attacks, strokes and other blood clot complications such as deep vein thrombosis in England and Wales in 2020 alone, although the excess risk to individuals remains small and reduces over time.
The research – involving a large team of researchers led by the Universities of Bristol, Cambridge, and Edinburgh, and Swansea University – shows that people with only mild or moderate disease were also affected. The authors suggest that preventive strategies, such as giving high-risk patients medication to lower blood pressure, could help reduce cases of serious clots.
Researchers studied de-identified electronic health records across the whole population of England and Wales from January to December 2020 to compare the risk of blood clots after COVID-19 with the risk at other times. Data were accessed securely and safely via the NHS Digital Trusted Research Environment for England, and the SAIL Databank for Wales.
In the first week after a COVID-19 diagnosis, people were 21 times more likely to have a heart attack or stroke, conditions which are mainly caused by blood clots blocking arteries. This dropped to 3.9 times more likely after 4 weeks.
‘Association of COVID-19 with major arterial and venous thrombotic diseases: a population-wide cohort study of 48 million adults in England and Wales’ by Jonathan A.C. Sterne et al. in Circulation [open access]