Blood clots are a serious health problem that affect millions of people around the world every year.
Some blood clots can block blood flow in important parts of the body and lead to life-threatening conditions such as heart attacks, strokes, or pulmonary embolism.
Now, researchers in Sweden have discovered three important genetic variants that may greatly increase the risk of dangerous blood clots forming in the legs.
The new study was carried out by scientists from Lund University in Sweden. The researchers found that certain gene variants can strongly raise the risk of venous thrombosis, a condition where blood clots form inside veins, usually in the legs.
In some people, having several of these risky genes increased the chance of blood clots by as much as 180 percent.
Blood clots can develop in arteries or veins, but the two types are very different. Arteries carry oxygen-rich blood away from the heart to the rest of the body. Veins carry blood back to the heart after oxygen has been used by the body.
Arterial clots often happen when fatty plaque inside blood vessels breaks apart. The body reacts as if there is an injury and forms a clot. These clots can suddenly block blood flow to the heart or brain, causing heart attacks or strokes.
Venous blood clots usually form for another reason. In the veins, blood moves more slowly, especially in the legs where blood must travel upward against gravity to return to the heart.
If blood flow becomes too slow, the body’s clotting system can become activated and create a blockage inside the vein. This condition is called venous thrombosis.
Sometimes part of the clot can break away and travel to the lungs. This causes a dangerous condition called pulmonary embolism, which can make breathing difficult and may become fatal if not treated quickly.
Although venous thrombosis is a major cause of death worldwide, experts say it often receives less public attention than heart attacks and strokes. In Sweden alone, more than 10,000 people develop venous thromboembolism every year.
Doctors have known for a long time that certain factors increase clot risk. Age is one important factor because blood circulation often becomes slower as people get older.
Obesity is another major risk because excess body weight can affect blood flow and increase pressure inside veins. Physical inactivity also raises risk because muscles help pump blood through veins during movement.
Interestingly, height also appears to play a role. Taller people may have a higher chance of developing blood clots because blood must travel a longer distance from the legs back to the heart. This can lead to slower blood flow in leg veins.
Researchers are also learning more about how diet may influence clotting. Some studies suggest that eating large amounts of ultra-processed foods could slightly raise clot risk, while healthier diets rich in plant foods may help lower it.
Scientists have also noticed that commercial fishermen appear to have a lower risk of blood clots, possibly because they eat more fish rich in omega-3 fatty acids.
Long periods of sitting or lying down are another important danger. Blood clots are more likely to form during long airplane flights, after surgery, or during illness that keeps people in bed for long periods. Pregnancy can also increase clot risk because the body naturally increases clotting ability to reduce bleeding during childbirth.
To lower risk during these situations, doctors may prescribe blood-thinning medications. Some people may also benefit from wearing compression stockings to improve blood flow in the legs.
Genetics are another major part of the story. One of the best-known inherited clotting mutations is called Factor V Leiden. About 10 percent of people in Sweden carry this mutation. It causes resistance to a natural protective protein called activated protein C, which normally helps prevent excessive clotting.
Scientists believe this mutation may have been helpful in ancient times because it reduced bleeding after injury or childbirth. However, in today’s world, where many people sit for long periods and live less active lifestyles, it may increase the risk of dangerous blood clots.
In the new study, researchers analyzed data from 30,000 people who participated in the Malmö Kost Cancer study. They examined 27 genes linked to the body’s clotting system.
The team discovered that three genetic variants called ABO, F8, and VWF were linked to a higher risk of venous thrombosis. Each gene increased risk by around 10 to 30 percent.
However, when several risk genes appeared together, the danger became much greater. People carrying five risk genes had a 180 percent higher risk of developing blood clots.
Unlike Factor V Leiden, which is mostly found in people of European ancestry, these newly identified variants are found in populations around the world. This means the findings could help improve clot prevention globally.
The researchers now hope to study whether doctors should use genetic information to decide how long patients need blood-thinning treatment after developing a clot.
The study also highlights how important healthy lifestyle habits are for preventing blood clots.
Staying active, avoiding long periods of sitting, maintaining a healthy weight, stopping smoking, exercising regularly, and eating a healthy diet may all help lower risk. Vaccinations may also play a role because infections can sometimes increase clotting risk.
The findings offer new insight into why some people are more likely to develop dangerous blood clots than others. By understanding both genetic and lifestyle risks, doctors may eventually create more personalized ways to prevent and treat venous thrombosis.
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