Where You Put on Pounds May Influence Clot Risk

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MONDAY, Oct. 26 (HealthDay News) -- The location of excess body fat appears to affect the risk of dangerous blood clots in veins, although that location differs in men and women, a new Danish study indicates.

The 10-year study found that bigger hips are associated with an increased risk of venous thromboembolism (VTE) in women but not men, while a wider waistline was associated with increased risk in men, according to a report published online Oct. 26 in the journal Circulation.

Obesity in general is an established risk factor for VTE, which occurs when a blood clot blocks a vein. When VTE happens in a leg, it is known as deep vein thrombosis. In a lung, it is a pulmonary embolism. A particularly deadly form of VTE, thromboembolism, occurs when a clot travels from a leg to a lung.

Researchers at Aarhus University Hospital followed more than 57,000 Danish men and women, aged 50 to 64 when the study started, assessing the relationships between body mass, fat distribution and VTE. The initial analysis showed that waist circumference was associated with VTE risk in both men and women.

"When hip circumference was adjusted for waist circumference, the association between hip circumference and VTE was eliminated for men but was still significant for women," the report said. "In contrast, when waist circumference was adjusted for hip circumference, the association between waist circumference and VTE was eliminated for women but was still significant for men."

"Further studies are needed to explain the associations," they wrote.

The Danish study results echoes those of an American study reported earlier this year, said Lyn Steffen, an associate professor of epidemiology at the University of Minnesota School of Public Health, and a leader of that study.

The Minnesota group followed more than 20,000 people for more than 12 years and found an association between VTE risk and metabolic syndrome, a constellation of risk factors including obesity, high blood pressure, insulin resistance and high blood cholesterol. A heightened risk of VTE was attributed to obesity.

"The message here is that obesity is a risk factor for venous thrombosis," Steffen said. "The effect of obesity in women might be the same as in men, but just is not measured in waist circumference."

It's possible that obesity increases the likelihood of developing blood clots, and it also might have a negative effect on the endothelium, the delicate lining of blood vessels, Steffen said.

"There is information that obesity contributes to inflammation, and it is associated with the metabolic syndrome, which predisposes to stroke," said Dr. Amytis Towfighi, an assistant professor of clinical neurology at the University of Southern California. "There may be similar effects in thrombotic disease, as well as mechanisms that are not well understood at this point."

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SOURCES: Lyn Steffen, Ph.D, associate professor, epidemiology, University of Minnesota School of Public Health, Minneapolis; Amytis Towfighi, M.D., assistant professor, clinical neurology, University of Southern California, Los Angeles; Oct. 26, 2009, Circulation, online