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Blood clots in the veins – particularly those that break off and travel to the lungs – can be fatal and have become increasingly so. Yet many adults know little about their risks or the growing evidence that healthy habits can help prevent clots.

"A key barrier in the United States is that awareness of this disease is not very good," Dr. Mary Cushman said of the condition known as venous thromboembolism.

VTE includes two types of clots: deep vein thrombosis, called DVT, usually in the leg, and pulmonary embolism, or PE, which is when a DVT breaks free and lodges in the lungs, where they often are fatal. There were roughly 370,000 PE and 857,000 DVT events in the United States in 2016, the last year for which statistics were available, according to .

Obesity and a lack of physical activity have long been associated with a higher risk for blood clots, along with family history, certain genetic factors and prior episodes of clotting.

Cushman, medical director of the Thrombosis and Hemostasis Program at the University of Vermont Medical Center in Burlington, has spent years researching the impact of obesity and other lifestyle factors on these clots.

Her work shows some of that risk can be lowered through lifestyle changes. Her , published last month in the journal Arteriosclerosis, Thrombosis, and Vascular Biology, measured the impact of seven metrics for cardiovascular health on people at high genetic risk for VTE. It found a strong association between two of those metrics – higher physical activity and ideal body weight – and a lower incidence of clots in people at high genetic risk.

"The size of the impact of physical activity and having a normal weight on reducing the risk of clots in those at high genetic risk was even more than I had imagined it might be," Cushman said. "If you have a high genetic risk for VTE and you did one to three bouts a week of physical activity (enough to work up a sweat), you'd have a 28% lower risk of developing clots. And, if your body mass index was less than 25, compared to someone who was obese (a BMI greater than 30), you'd have a 45% lower risk."

The seven metrics, known as the 91ÊÓƵ's Life's Simple 7, also include smoking status, total cholesterol, diet score, blood pressure and fasting glucose.

"Not all of these habits confer the same benefit," said Dr. Peter Henke, a vascular surgeon who was not involved with the recent study.

"If you have a known family history of VTE, or if you have had a clot in the past, the message here is that for the most part, you can modify your risk for having a future clot," said Henke, the Leland Ira Doan Professor of Vascular Surgery at the University of Michigan in Ann Arbor. "If you know you are at high risk, it is an impetus to adopt these seven lifestyle habits, which, frankly, everyone should adopt anyway."

PE and DVT kill up to 100,000 Americans each year, according to the . A study published in August in the found death rates for pulmonary embolism for the overall population, which had been falling, began rising over the past decade, with the biggest increases seen in those under 65.

Cushman encourages people to learn the symptoms of VTE. They include swelling, pain or tenderness in the legs, red streaks or other skin discoloration, and skin that feels warm to the touch. Symptoms of pulmonary embolism include shortness of breath, rapid breathing, chest pain, a rapid heart rate or lightheadedness.

And find out your family history, she said. "If you have a close relative who had a clot, then your risk is twice as high as other people. The more first-degree relatives you have who had clots – those are parents, children or siblings – the higher your risk."

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