一项新的研究表明，感染新冠肺炎病毒会增加患严重血栓的风险。

一个由瑞典、英国和芬兰研究人员组成的国际团队将2020年2月至2021年5月期间瑞典100多万确诊病例与400万检测呈阴性的对照患者进行了比较。

根据周三发表在《BMJ》杂志上的结果，他们发现，在感染新冠肺炎病毒三到六个月后，患者被诊断出腿部或肺部有血栓的风险增加。

具体来说，在新冠肺炎感染后的三个月内，患者患深静脉血栓的风险增加了4%，深静脉血栓是一种在大腿或小腿深处形成的血栓。

患者患肺栓塞的风险也增加了17%，肺栓塞是一种在血管中形成的凝块，会在感染病毒后长达六个月的时间里传播到肺动脉。

该团队表示，他们的结果增加了越来越多的证据，表明新冠肺炎和严重的血栓之间存在联系，同时增加了关于这种风险可能持续多久的新信息。

“目前的发现具有重大的政策含义，”作者写道，并补充说，该报告“加强了预防新冠肺炎疫苗接种的重要性。”

他们还表示，研究结果表明，新冠肺炎患者——“特别是高危患者”——应该服用抗凝药物，这些药物有助于防止这些血栓。

在研究期间，该小组在新冠肺炎患者中发现了401例DVT，而在阴性患者中发现了267例。

同时，在病毒患者中有1，761例PE，而对照患者中有171例。

如果新冠肺炎患者有基础疾病，有严重的病毒病例，或者在2020年初第一波疫情期间感染，他们患血栓的风险更高。

然而，不仅仅是血栓的风险。该研究还发现，在新冠肺炎感染后长达两个月的时间里，任何类型的出血风险都会增加。

该小组指出存在局限性，包括该研究是观察性的，而不是随机对照试验。

此外，研究人员认识到，新冠肺炎患者的凝血功能可能诊断不足，而且患者的疫苗接种情况也不清楚。

丹尼尔奈顿/盖蒂图片社

在参加开幕夜比赛之前，一名球迷在新冠肺炎测试场擦拭...

尽管新冠肺炎病毒感染后出现血栓的风险已被充分证实，但还不知道是什么生物机制在起作用。但是，有理论。

一个研究来自密歇根大学医学和美国国家心肺血液研究所的研究表明，来自新冠肺炎感染的“流氓”抗体会导致血细胞失去抗凝血特性。

另一个研究耶鲁大学医学院的研究人员认为，由于病毒引起的炎症，内皮细胞(排列血管的细胞)产生特定的蛋白质，导致血栓。

作者写道:“新型冠状病毒感染增加静脉血栓栓塞或出血的风险是否比呼吸道感染(如流感)更大，还有待确定，而且是否应该延长新冠肺炎后的[抗凝药物]期限。”

COVID-19 infection increases risk of serious blood clots 3 to 6 months later: Study

Being infected with COVID-19 raises the risk of developing serious blood clots, a new study suggests.

An international team of researchers from Sweden, the United Kingdom and Finland compared more than 1 million people in Sweden with a confirmed case of the virus between February 2020 and May 2021 to 4 million control patients who tested negative.

They found three to six months after contracting COVID-19, patients were at increased risk of being diagnosed with blood clots in their legs or lungs, according to results published in the journal BMJ on Wednesday.

Specifically, patients had a 4% raised risk of deep vein thrombosis, a blood clot that forms deep in the thigh or the lower leg, up to three months after a COVID-19 infection.

Patients also had a 17% heightened risk of developing a pulmonary embolism, a clot that develops in a blood vessel and travels to a lung artery, up to six months after having the virus.

The team said its results add to a growing body of evidence about the link between COVID-19 and serious blood clots, while adding new information about how long the risk might last.

"The present findings have major policy implications," the authors wrote, adding that the report "strengthens the importance of vaccination against COVID-19."

They also said the findings suggest that COVID-19 patients -- "especially high-risk patients" -- should take anticoagulation medicine, which are medications to help prevent these clots.

During the course of the study period, the team saw 401 cases of DVT among the COVID-19 patients, compared to 267 cases among the negative patients.

Meanwhile, there were 1,761 cases of PE among virus patients in comparison with 171 cases among the control patients.

COVID-19 patients were at higher risk of blood clots if they had underlying conditions, had a severe case of the virus or if they were infected during the first wave of the pandemic in early 2020.

However, there wasn't just a risk of blood clots. The study also found an increased risk of any kind of bleeding up to two months after a COVID-19 infection.

The team noted there were limitations, including that the study was observational rather than a randomized controlled trial.

Additionally, the researchers recognized that clotting in COVID-19 patients may be underdiagnosed and information about patients' vaccination status was not available.

Despite the risk of blood clots following COVID-19 infections being well-documented, it's unknown what biological mechanisms are at play. However, there are theories.

Onestudyfrom Michigan Medicine and the U.S. National Heart, Lung and Blood Institute suggested "rogue" antibodies from a COVID-19 infection cause blood cells to lose their anti-clotting properties.

Anotherstudyfrom Yale School of Medicine suggested specific proteins are produced by endothelial cells -- cells that line blood vessels -- due to inflammation from the virus and lead to blood clots.

"It remains to be established whether SARS-CoV-2 infection increases the risk of venous thromboembolism or bleeding more than it does for respiratory infections, such as influenza, but also whether the period of [anticoagulation medicine] after COVID-19 should be extended," the authors wrote.