Covid-19: associated with a higher risk of developing thrombosis and embolism - Health

A person who has had COVID-19 is at increased risk of developing a serious blood clot within six months of having the illness.

This is one of the main conclusions of a recent study carried out in Sweden and published in the specialized magazine British Medical Journal (BMJ).

The research also found that people with severe covid, especially those who had to be hospitalized, and those infected during the first wave had the highest risk of clots.

The study does not state that covid-19 was the cause of these clots, but it does identify infection as a risk factor for developing thrombi, that is, blood clots inside a blood vessel.

To reach these conclusions, the researchers tracked the health status of more than one million people who tested positive for COVID between February 2020 and May 2021 in Sweden, and compared them with four million people of the same age and gender. who had not tested positive.

According to the authors of the research, their findings highlight the importance of getting vaccinated.

the findings

The study showed that after a covid-19 infection the risk of:

Develop Deep venous thrombosis (DVT), which are blood clots in the leg, within three months.
Develop pulmonary embolism, which are blood clots in the lungs, within six months.
Internal bleeding, such as strokewithin a period of two months.

Comparing the risks of blood clots after covid-19 with the normal level of risk, they found that:

4 in 10,000 covid patients developed DVT, compared to 1 in 10,000 people who did not have covid.
About 17 in 10,000 Covid patients had a blood clot in the lung, compared to less than one in 10,000 who did not have Covid.

The study argues that the increased risk of blood clots was higher in the first wave of the pandemic, likely because treatments improved over the following months and older patients started getting vaccinated in the second wave.

That result was “expected”, according to Dr. Inmaculada Roldán Rabadán, cardiologist of the Cardiovascular Thrombosis Group of the Spanish Society of Cardiology, in statements collected by the Science Media Center Spain portal.

“So we had fewer tools to manage the disease,” he explains.

The risk of a blood clot in the lung in people who were severely ill with covid was shown to be 290 times higher than normal, and seven times higher than normal after mild covid.

Mild covid was not found to increase the risk of internal bleeding.

“Good reason to get vaccinated”

Blood clots can also occur even after getting vaccinated, but the risk is much lower, according to a study led by the University of Oxford in August 2021.

“For unvaccinated people, that’s a very good reason to get vaccinated: the risk is much higher than the risk of the vaccines,” says Anne-Marie Fors Connolly, a researcher at the Department of Clinical Microbiology at Umea University in Sweden and lead author of the study.

Frederick K Ho, a professor of public health at the University of Glasgow who was not involved in the study, argues that although the risk of blood clots increases after vaccination, “the magnitude of the risk remains smaller and persists for a shorter period than that associated with infection.

Covid and clots

The study does not prove that covid is the cause of blood clots.

With this type of study “we can only determine if there is an association between covid-19 and blood clots or bleeding,” Fors Connolly tells BBC Mundo.

The expert adds that to establish a causal relationship, other types of studies would be necessary.

“The data is clear in showing that there is an association (between covid-19 and clots), but what is not totally clear is how that association works,” Jon Gibbins, director of the Cardiovascular Research Institute, tells BBC Mundo. and Metabolic at the University of Reading, who was not involved in the research.

“Further efforts are needed to determine whether this is due to a long-standing inflammatory condition or some form of long-standing immune dysfunction,” Gibbins adds.

Still, researchers believe the clots could be caused by the virus’s direct effect on the layer of cells lining the blood vessels, an exaggerated inflammatory response to the virus, or the body forming blood clots at inappropriate times.

Frederick K Ho says this study “reminds us of the need to remain vigilant for complications associated with even mild covid infection, including thromboembolism.”

For her part, Dr. Roldán Rabadán concludes that this research “is highly relevant for the management of the disease in the future.”

*With information from Philippa Roxby and Carlos Serrano.

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