Blood clots in the legs are more common and more dangerous than many people realize. This condition, called venous thrombosis, happens when blood thickens and forms a blockage inside a vein, usually in the legs.
If part of the clot breaks off and travels to the lungs, it can cause a life‑threatening emergency known as a pulmonary embolism. Although heart attacks and strokes often receive more public attention, clots in the veins are also a major cause of death around the world.
Scientists in Sweden have now discovered new genetic clues that may explain why some people are much more likely to develop these clots. Researchers from Lund University studied thousands of people and identified three specific gene changes that raise the risk of venous blood clots.
People who carried several of these genetic variants had a much higher chance of developing the condition, in some cases up to 180 percent higher than those without them. This discovery helps explain why clots can happen even in people who appear otherwise healthy.
Blood clots can form in two main types of blood vessels: arteries and veins. Arteries carry oxygen‑rich blood from the heart to the body, while veins carry blood back to the heart. Clots in arteries usually happen when fatty buildup inside the vessel wall breaks open, causing the body to react as if there is an injury.
These clots can block blood flow to the heart or brain, leading to heart attacks or strokes. Venous clots are different. They often form when blood flow becomes slow, such as during long periods of sitting, illness, or recovery after surgery.
Age, body weight, and even height can affect the risk. As people grow older, the blood vessels and circulation system change, making clots more likely. Obesity also increases risk because extra body weight can slow blood flow and change the balance of clotting substances in the body.
Interestingly, tall people may also face a higher risk because blood has a longer distance to travel from the legs back to the heart, which can lead to slower circulation.
Lifestyle factors play a role as well. Sitting for long periods, such as on long flights or during long workdays, can reduce blood movement in the legs. Pregnancy also raises the risk because the body naturally increases clotting ability to prevent bleeding during childbirth. Diet may matter too.
Some research suggests that diets high in heavily processed foods could slightly increase risk, while diets rich in plant foods and healthy fats may help protect against clots. For example, fishermen who eat a lot of omega‑3 fatty acids from fish have been found to have a lower risk.
Genetics, however, can strongly influence a person’s chances of developing a clot. One well‑known inherited condition is called Factor V Leiden, which affects many people of European background. It changes how the body controls clotting, making clots more likely to form.
The new Swedish study adds to this knowledge by identifying three additional gene variants, known as ABO, F8, and VWF, that also increase risk. Unlike Factor V Leiden, these gene changes are found in people all over the world, meaning the findings could help doctors globally.
To make this discovery, researchers examined data from about 30,000 people who participated in a long‑term health study. They looked at genes involved in blood clotting and compared them with medical records showing who had developed clots.
The results showed that each of the three gene variants raised risk by 10 to 30 percent, and having several of them together greatly increased the danger.
Understanding genetic risk could help doctors decide how to prevent future clots. For example, people with higher genetic risk might benefit from longer treatment with blood‑thinning medicine after a clot or during high‑risk situations. It may also encourage earlier screening and lifestyle changes.
Even though genetics cannot be changed, many steps can lower the risk of venous blood clots. Staying physically active, maintaining a healthy weight, avoiding smoking, and moving regularly during long trips can all help keep blood flowing smoothly.
Recognizing the warning signs, such as leg swelling, pain, or redness, is also important so treatment can begin quickly.
This research shows that blood clots are not caused by one single factor. Instead, they result from a combination of genetics, lifestyle, and health conditions. By learning more about these hidden risks, scientists hope to prevent more cases and save lives in the future.
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