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Deep Vein Thrombosis Health Center

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Being Tall, Obese May Boost Risk of Blood Clots

Risk Highest for Men, but Researchers Don't Know Why Height Plays a Role

Risk of Blood Clots: Short vs. Tall, Obese vs. Not continued...

Compared to the short, normal-weight men:

  • Obese, tall men had a 5.28 times higher risk of clots
  • Normal-weight and tall men -- with tall defined as at least 5 feet, 11.7 inches -- had a 2.57 times higher risk
  • Obese, short men had a 2.11 times higher risk.

Women were defined as short if they were 5 feet 2.6 inches or less. Normal-weight again was defined as having a BMI below 25; obesity was defined as a BMI of 30 or higher.

Compared to short, normal-weight women:

  • Obese, tall women -- anyone more than 5 feet, 6 inches -- had a 2.77 times higher risk of clots
  • Obese, short women had a 1.83 times higher risk
  • Normal-weight, tall women had no increased risk

Behind the Link

Exactly why the link between height, obesity, and blood clots occurs is not known, Braekkan says. In taller people, the blood must be pumped a longer distance. That may cause reduced blood flow in the legs and raise clot risk.

Obesity is linked with constant low-grade inflammation, and that may make blood more prone to clot, the researchers speculate.

''It may be that tall people have more venous valves," Braekkan says. "Venous clots often originate in the area around a venous valve pocket. Height is to a high degree genetically determined. Though it seems unlikely, it cannot be ruled out that height and unrecognized venous clot risk factors have shared genetics."

Advice for Tall, Obese Men and Women

''The most important [advice] is to stay slim or lose weight when obese," Braekkan says. Doctors should take into account body height and weight when considering a patient's risk for blood clots, Braekkan says.

Ravi Dave, MD, a staff cardiologist at Santa Monica-UCLA Medical Center & Orthopaedic Hospital in Santa Monica, Calif., agrees. A tall, obese person should take extra precautions to avoid blood clots, he tells WebMD. That is especially true, he says, if they are in situations that raise the risk, such as taking a long airplane flight.

"Wear loose clothing, try for an aisle seat, get up and walk around," he says. Smoking also increases the risk, he says.

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