Most people are now aware of the possibility of getting long COVID after getting COVID-19. However, recent studies indicate that the virus may increase your risk of blood clots, and that risk may persist above average for a year after the virus has been treated.
That is the main finding of a sizable new study that was released in the publication Circulation. 48 million individuals registered in the National Health System of Great Britain between January 2020 and the day COVID-19 vaccines became available in December 2020 were the subject of the study’s analysis. The researchers discovered 1.4 million diagnoses of COVID-19, and 10,500 of those patients experienced problems with blood clots.
The risk of developing an arterial blood clot, which can cause a heart attack or stroke by obstructing blood flow to the heart or brain, increased nearly 22 times in the first week following a COVID-19 diagnosis, according to the researchers. By the second week, the risk had decreased somewhat but remained high—less than four times higher than in the case of a person who was virus-free.
The risk was 33 times higher in the first week following a COVID-19 diagnosis for blood clots that form in the veins, such as deep vein thrombosis and pulmonary embolism. It was about eight times higher three to four weeks after a person was diagnosed. Between 27 and 49 weeks later, the risk was still 1.8 times higher compared to individuals who had never received COVID-19.
No matter how severe a person’s COVID-19 infection was, there was still a risk, but it was greater in hospitalized patients. Patients who were Black and Asian also had higher clot risks.
The clots were generally uncommon. In the 49 weeks following a COVID-19 diagnosis, the risk of developing an arterial clot was 0.5% overall, and the risk of developing a venous clot was 0.25%. (To translate that into actual health problems, it resulted in an additional 3,500 cases of pulmonary embolism, deep vein thrombosis, or other vein-related illnesses, as well as an additional 7,200 heart attacks or strokes.)
Why does COVID-19 put you at greater risk for blood clots?
There are a few theories as to why this connection might exist, but the study didn’t investigate this; it simply found an association.
One major one is that the virus can lead to bodily inflammation. Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security and an infectious disease specialist, claims that COVID causes an inflammatory response that can increase blood clotting and harm vascular structures. Therefore, “a heightened risk of clotting can persist,” he claims.
According to Thomas Russo, M.D., professor and director of infectious diseases at the University at Buffalo in New York, it’s also possible that the virus itself causes an increased risk of blood clots. He claims that it “seems to be part of the pathophysiology of this virus.”
According to Dr. Russo, medical professionals have known “since the start of this pandemic” that people who contract COVID have a higher propensity to clot their blood. He claims that early on, because of blood clots, “we were seeing these terrible situations of people with black fingers and toes, and damage to a variety of organs.”
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Can other infections cause this to occur?
According to medical professionals, other infections can increase the risk of blood clots. Dr. Adalja emphasizes that the connection between shingles and an elevated risk of heart attacks is “well described.”
According to Dr. Russo, “These clots have also been associated with the flu.” They are more frequent with COVID, though.
Blood clot warning signs
Blood clotting is typical in certain situations, such as after a cut. According to Medline Plus, blood clots can be problematic if they develop into a blockage or spread to other parts of the body like the lungs or brain. Depending on where in the body a dangerous clot is, different symptoms may be present. According to Medline Plus, these might be
- Stomach pain
- Nausea
- Vomiting
- Sudden or gradual pain in your arm, along with swelling, tenderness, and warmth
- Shortness of breath
- Pain with deep breathing
- Rapid breathing
- An increased heart rate
- Trouble speaking
- Vision problems
- Seizures
- Weakness on one side of the body
- A sudden, severe headache
- Chest pain
- Sweating
- Shortness of breath
- Pain in the left arm
How to prevent blood clots after having COVID-19
Dr. Adalja emphasizes how uncommon this risk is. But according to Dr. Russo, it’s still a good idea to at least be knowledgeable about the possibility of blood clots and the symptoms they can present with.
Whether you have COVID or not, Dr. Russo advises getting the entire COVID-19 immunization series, including any boosters you may be eligible for. This serves as yet another justification for trying to avoid contracting COVID, he says.