London, Apr 7: People infected with SARS-CoV-2, the virus that causes COVID-19, have an increased risk of developing serious blood clots for up to six months after the infection, even in mild cases, according to a study published in The BMJ.
The 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 a bleeding event up to two months.
They also show a higher risk of events in patients with underlying conditions, patients with more severe COVID-19, and during the first pandemic wave compared with the second and third waves.
The researchers from Umea University in Sweden noted that these results support measures to prevent thrombotic events, especially for high risk patients, and strengthen the importance of vaccination against COVID-19.
Using national registries in Sweden, they identified more than one million people with confirmed SARSCoV-2 infection between February 1, 2020 and May 25, 2021, matched by age, sex, and county of residence to more than four million people who had not had 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 -- before and long after COVID-19 diagnosis -- and compared it to the rates in different time intervals after COVID-19 diagnosis.
They then calculated the rates of deep vein thrombosis, pulmonary embolism, and bleeding 1-30 days after COVID-19 diagnosis in the COVID-19 group and compared them to the corresponding rates in the control group.
The results show that compared with the control period, risks were significantly increased 90 days after COVID-19 for deep vein thrombosis, 180 days for pulmonary embolism, and 60 days for bleeding.
After taking account of a range of potentially influential factors, the researchers found a five-fold increase in risk of deep vein thrombosis, a 33-fold increase in risk of pulmonary embolism, and an almost twofold increase in risk of bleeding in the 30 days after infection.
This means that a first deep vein thrombosis occurred in 401 patients with COVID-19 and 267 control patients, the researchers said.
A first pulmonary embolism event occurred in 1,761 patients with COVID-19 and 171 control patients, and a first bleeding event occurred in 1,002 patients with covid-19 and 1,292 control patients, they said.
The researchers found that the risks were highest in patients with more severe COVID-19 and during the first pandemic wave compared with the second and third waves, which they said could be explained by improvements in treatment and vaccine coverage in older patients after the first wave.
Even among mild, non-hospitalised COVID-19 patients, the researchers found increased risks of deep vein thrombosis and pulmonary embolism.
No increased risk of bleeding was found in mild cases, but a noticeable increase was observed in more severe cases.
This is an observational study, so the researchers cannot establish cause, and they acknowledge several limitations which might have affected their findings.
For example, they said VTE may have been underdiagnosed in patients with COVID-19, testing for the disease was limited, especially during the first pandemic wave, and information on vaccination was not available.
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Jaipur, Mar 28: Young Riyan Parag showed why he is considered a precocious talent as he struck a stunning 84 not out off 45 balls to set up a 12-run win for Rajasthan Royals against Delhi Capitals in their IPL match here on Thursday.
Sent in to bat, RR were reduced to 36 for 3 in the eighth over but the 22-year-old Parag single-handedly took the home side to 185 for 5 with a magnificent unbeaten knock studded with seven fours and six sixes.
Parag, who was promoted to number 4 by the team management this season and made 43 in the previous match, took 25 runs off veteran South African pacer Anrich Nortje with scores of 4, 4, 6, 4, 6, 1 in the final over to hit his highest T20 score.
Chasing 186 for a win, DC could only manage 173 for 5 in 20 overs though South African youngster Tristan Stubbs (44 not out off 23 balls) kept them in the hunt till the final over from which they needed 17 runs.
Avesh Khan conceded just four runs to help RR win their second consecutive match.
South African pacer Nandre Burger and Yuzvendra Chahal took two wickets apiece to also contribute in the RR win.
"Definitely disappointed. The best thing to do from here is to learn from it. The bowlers did well through the 15-16 overs. But the batters did well at the death, hopefully we do better in the next game," DC skipper Rishabh Pant said.
DC were reduced to 34 for 2 in the fourth over with Burger taking two wickets in three balls in a fine display of fast bowling.
Burger, who was brought in as Impact Sub for Shimron Hetmyer, dismissed opener Mitchell Marsh (23 off 12 balls) and Ricky Bhui (0) in the fourth over.
DC captain Rishabh Pant came out to bat at the fall of Bhui's wicket and along with senior batter David Warner built the innings without taking too much risk. Delhi were 89 for 2 at the halfway stage.
Warner was the more aggressive one as he got the boundaries to keep DC in the hunt. The senior Australian batter fell one run short of his fifty courtesy a brilliant diving catch by Sandeep Sharma off the bowling of Avesh in the 12th over.
Warner and Pant were involved in a crucial 67-run partnership for the third wicket.
Playing in his 100th IPL match and 14 months after a horrible car crash, Pant tried to build the innings with occasional boundaries. But he got out for a 26-ball 28 as Chahal induced a faint lower edge for Sanju Samson to do the rest behind the stumps in the 14th over.
The asking rate shot up to more than 13 runs an over and DC needed 66 from the last five overs.
Stubbs kept DC in the game with two consecutive sixes off Ravichandran Ashwin in the 17th over, but in the end the Delhi side were short by 12 runs.
They needed 34 runs from the final two overs which they could not get. It was DC's second consecutive loss.
Earlier, Parag shared 54 and 52 runs respectively with Ravichandran Ashwin (29) and Dhruv Jurel (20) after RR made a shaky start.
Royals captain Samson struck three consecutive boundaries in the fourth over bowled by pacer Mukesh Kumar before nicking a Khaleel Ahmed delivery two overs later to Pant to get out for 15.
RR were 30 for 2 by then as Mukesh had given DC their first breakthrough with the wicket of Yashasvi Jaiswal (5).
The Royals were in more trouble after wrist spinner Kuldeep Yadav literally forced his captain Pant to take a review, which later proved to be successful, to dismiss Englishman Jos Buttler for an LBW decision.
Ashwin came out to bat at number five and he lofted a Kuldeep delivery for a six to help RR reach 58 for 3 at halfway stage. He gave Nortje even a harsher treatment with two sixes in the next over that yielded 15 runs.
Ashwin, however, holed out to Tristan Stubbs near the boundary ropes for a 19-ball 29.
Parag then made his presence felt, striking two boundaries and a six off Ahmed to take RR past 100 in the 15th over.