People infected with COVID-19 have an increased risk of serious blood clots for up to 6 months.
London:
According to a study published in The BMJ, people infected with SARS-CoV-2 have an increased risk of developing severe blood clots up to six months after infection, even in mild cases.
Researchers found an increased risk of deep vein thrombosis – a blood clot in the leg – up to three months after COVID-19 infection, pulmonary embolism – a blood clot in the lung – up to six months, and bleeding events up to two months.
They show a higher risk of events in patients with underlying conditions, in patients with more severe COVID-19, and during the first pandemic wave compared to the second and third waves.
Researchers from Ume University in Sweden noted that these results support measures to prevent thrombotic events, especially for high-risk patients, and reinforce the importance of vaccination against COVID-19.
Using national registries in Sweden, they identified more than one million people with confirmed SARSCoV-2 infections between February 1, 2020 and May 25, 2021, up to four million according to age, gender and county of residence. Matched more people than those who didn’t. A positive SARS-CoV-2 test result.
The researchers first calculated the rates of deep vein thrombosis, pulmonary embolism, and bleeding in COVID-19 individuals during a control period — both before and long after a COVID-19 diagnosis — and compared it with those after COVID-19. rates at different time intervals. 19 Diagnosis.
They then calculated the rates of deep vein thrombosis, pulmonary embolism, and hemorrhage in the COVID-19 group 1–30 days after COVID-19 diagnosis and compared them with the respective rates in the control group.
The results showed that there was a significantly increased risk of 90 days post-COVID-19 for deep vein thrombosis, 180 days for pulmonary embolism and 60 days for hemorrhage, compared to the control period.
Taking into account a range of potentially influencing factors, the researchers found that there was a five-fold increase in the risk of deep vein thrombosis, a 33-fold increase in the risk of pulmonary embolism, and a nearly two-fold increase in the risk of bleeding over 30 days. Is. after infection.
This means that the first deep vein thrombosis occurred in 401 patients with COVID-19 and 267 control patients, the researchers said.
The first pulmonary embolism event occurred in 1,761 patients with COVID-19 and 171 control patients, and the first bleeding event in 1,002 patients with COVID-19 and 1,292 control patients, they said.
The researchers found that the risk was highest in patients with more severe COVID-19 and during the first pandemic wave, compared to the second and third waves, which they said followed the first wave of treatment and vaccines in older patients. Could be explained by the improvement in coverage. ,
Even in mild, non-hospitalized COVID-19 patients, researchers found an increased risk of deep vein thrombosis and pulmonary embolism.
No increased risk of bleeding was found in mild cases, but a significant increase was observed in more severe cases.
This is an observational study, so the researchers cannot establish causation, and they acknowledge a number of limitations that may affect their conclusions.
For example, he said VTE may have been underdiagnosed in patients with COVID-19, that testing for the disease was limited, especially during the first pandemic wave, and vaccination information was not available.
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