Sweating Over Economy-Class Tickets?
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The data, says Scurr, point to the effectiveness of elastic stockings to reduce risk of blood clots after surgery. He writes, "our findings strongly suggest that stockings also protect against symptomless DVT after air travel."
Scurr further indicates that his numbers may be conservative because ultrasound detects from 79% to 99% of calf vein thrombosis. "Our data may have underestimated the true rate of calf vein thrombosis by as much as 30%," he writes. But others have their own opinion about the study.
"Potentially flawed study," says Jack Hirsh, MD, director of the Hamilton Civic Hospital Research Center at McMaster University in Ontario.
Hirsh has run some epidemiological numbers of his own: "In the general population, a 20-year-old has a 1/5,000 risk per year; an 85-year-old has a 1/100 risk because of age and other illnesses; middle-aged people fall somewhere in the middle, from 1/1,000 to 1/500 per year -- if they don't fly," Hirsh tells WebMD. "Flying may increase thrombosis by 1/25."
The bottom line is that there is a "very low risk, even if you are flying," says Hirsh.
Who is at risk of DVT? Those who have family history or multiple episodes of thrombosis, as well as patients with active cancer, Hirsh tells WebMD
So why did Scurr get such high numbers? "They were looking for silent clots, and what they found were very small [ones] that were of no risk to anyone," says Hirsh. "These teeny-weeny clots are absolutely meaningless. It's even possible that if we were to look in our legs after lying in bed for eight hours we would find them."
Hirsh's bottom-line message: "In the otherwise healthy individual, the risk of clotting is very low," he tells WebMD. "It's a very uncommon event."
If you are still concerned and want to hedge your bets, Hirsh offers suggestions: Practice isometric exercises -- muscle contractions -- for five minutes every half hour, or do them for one minute every 10 minutes. "Those numbers are just pulled out of the air," he says. "The point is, contracting your muscles frequently pushes blood up towards your heart."