Covid-19 increases risk of severe blood clots by one year: study

Infection with SARS-CoV-2 increases the risk of developing potentially life-threatening blood clots for at least 49 weeks, according to a UK study.

The research, recently published in the journal Circulation, found that in the first week after being diagnosed with COVID-19, people were 21 times more likely to have a heart attack or stroke, conditions mainly caused by blood clots in the arteries.

After 4 weeks, the probability was reduced to 3.9 times, according to the study.

The team, led by researchers from the Universities of Bristol, Cambridge, Edinburgh and Swansea, UK, also studied conditions caused by blood clots in the veins, such as deep vein thrombosis and pulmonary embolism, the latter of which can be fatal.

They found that in the first week of diagnosis, people were 33 times more likely to develop blood clots in their veins, and after 4 weeks, they were 8 times more likely.

While the risk of developing blood clots after COVID-19 remained for the entire duration of the study, from week 26 to week 49, the likelihood of blood clots decreased to 1.3 times in the arteries and 1.8 times in the veins.

“We are reassured that the risk is dropping very rapidly especially for heart attacks and strokes, but finding that it has been high for some time highlights the long-term effects of COVID-19 that we are just beginning to understand,” said Jonathan Stern, who shared in leadership of the study.

The researchers also found that people with mild or moderate illness who were not admitted to hospital were also affected, although the increased risk was not as high as those with severe illness requiring hospitalization.

We showed that even people who were not hospitalized had a higher risk of developing blood clots in the first wave, although the risk to individuals is still small, said Angela Wood, another study co-leader.

Researchers studied de-identified electronic health records across all residents of England and Wales from January to December 2020 to compare the risk of blood clots after COVID-19 with risks at other times.

The data was collected in 2020, before mass vaccination was launched in the UK, and before the most recent outbreaks of COVID-19 such as Delta and Omicron.

The study authors suggest that preventive strategies, such as giving medications to lower blood pressure to high-risk patients, can help reduce the incidence of dangerous clots.

said William Whiteley, who co-led the study.

Researchers are now studying data beyond 2020 to understand the impact of vaccination and the impact of newer variables.

(The title and image for this report may have been reworked only by the Business Standard staff; the rest of the content is automatically generated from a shared feed.)