Scientists in Sweden have identified three genetic changes that can greatly increase a person’s risk of developing blood clots in the legs, a condition known as venous thrombosis.
The discovery gives researchers a better understanding of why some people are more likely than others to develop these potentially dangerous clots and may eventually help doctors identify people who need extra protection.
Blood clots are a serious health problem around the world. They can develop in either arteries or veins, but these clots form in different ways and lead to different health problems.
Arterial blood clots usually happen when fatty deposits called plaque build up inside blood vessels and eventually break apart. The body treats this as an injury and forms a clot. If this clot blocks blood flow to the heart, it can cause a heart attack. If it blocks blood flow to the brain, it can lead to a stroke.
Venous blood clots, however, usually develop in the deep veins of the legs. They occur when blood moves too slowly and begins to collect in the veins. This slower blood flow activates the body’s clotting system and can cause a blockage inside the vein.
A clot in the leg is known as deep vein thrombosis. If part of the clot breaks off and travels to the lungs, it can cause a pulmonary embolism, a life-threatening condition that can make breathing difficult and may lead to death if not treated quickly.
Although venous thrombosis receives less public attention than heart attacks and strokes, it is a major cause of illness and death. In Sweden alone, more than 10,000 people develop this condition each year. Similar cases occur throughout the world, affecting people of all ages, although the risk rises with age.
Several factors can increase the chance of developing blood clots in the legs. Older adults are at higher risk because blood circulation tends to slow down with age. Being overweight is also an important risk factor because excess body weight can slow blood flow and change the levels of certain clotting substances in the body.
Tall people also appear to have a greater risk. Scientists believe this is because blood must travel a longer distance from the legs back to the heart, making it easier for blood to pool in the leg veins.
Lifestyle habits also play a role. Eating large amounts of ultra-processed foods may slightly increase the risk, while diets rich in fruits, vegetables, whole grains, and other plant-based foods may offer some protection.
Interestingly, one study found that commercial fishermen had a lower risk of blood clots, possibly because they consume more fish that contain omega-3 fatty acids.
Periods of prolonged inactivity can also trigger blood clots. Sitting for many hours on long flights, staying in bed after surgery, or recovering from an illness can all slow blood flow in the legs.
Pregnancy also increases risk because the body naturally produces more clotting factors and reduces some protective proteins to prepare for childbirth. Doctors sometimes prescribe blood-thinning medicines in these situations to help prevent dangerous clots.
Genes are another important piece of the puzzle. One well-known genetic mutation is called Factor V Leiden. It is found in about 10% of people in Sweden and is particularly common among people with European ancestry.
This genetic change interferes with one of the body’s natural anti-clotting mechanisms. Scientists believe it may have been beneficial in ancient times because it reduced the risk of severe bleeding, but in today’s less active lifestyle, it can increase the chance of harmful clots.
In the new study, researchers from Lund University examined genetic information from about 30,000 participants in the Malmö Diet and Cancer Study. They analyzed 27 genes involved in blood clotting and discovered that three genes called ABO, F8, and VWF significantly increased clotting risk.
Each of these genetic variants raised the risk by about 10% to 30%. People who carried five clotting-related risk genes had almost twice the risk of developing venous thrombosis compared with those who carried fewer risk genes.
Unlike Factor V Leiden, which is largely limited to European populations, these three newly identified genetic variants are found in people around the world. This means the findings could have global importance and may help doctors improve risk assessments for many different populations.
The researchers now hope to determine whether people with multiple clotting-risk genes might benefit from longer use of blood-thinning medications after experiencing a blood clot. In the meantime, there are practical steps people can take to lower their risk.
Staying physically active, avoiding sitting for long periods, maintaining a healthy weight, eating a balanced diet, quitting smoking, wearing compression stockings when recommended, and following medical advice can all help reduce the chances of developing dangerous blood clots.
The study shows that blood clots result from a complex combination of genetics, lifestyle, and other health factors. Understanding both inherited and everyday risks may help people take preventive action and protect themselves from one of the world’s major causes of illness and death.
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