I don’t take long plane flights all that often, but when I do, I make sure to book an aisle seat. I need the room to stretch my legs and get up whenever I want, without having to bother a slumbering seatmate.
I’m also partly motivated by recent studies that suggest that sitting too long in a cramped airplane seat can cause deep vein thrombosis (DVT), potentially deadly blood clots that form in the legs and can migrate to the heart or brain. I know someone who died of DVT an hour after getting off a long flight, while she was driving herself home from the airport.
But now in a new set of guidelines on blood clots, the American College of Chest Physicians says that the risk for most airline travelers is low. On short flights, there appears to be no increased risk of DVT, and on long flights (more than four hours), the risk increases only slightly to once every 4,600 flights. Overall, however, the absolute risk of a blood clot among healthy passengers is “very, very low,” says Dr. Gordon Guyatt, professor of medicine at McMaster University and the chair of the panel that wrote the new guidelines.
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Blood clots can form during inactivity because the leg muscles that normally push blood back to heart aren’t being used. That results in blood pooling in the veins in the leg, increasing the risk of clotting. That’s why getting up periodically during a long flight isn’t a bad idea. The guidelines found that flights lasting longer than eight hours are riskiest.
The new advice is based on a review of research and other data on DVT, and also suggests that sitting in the window seat appears to increase DVT risk. But, says Guyatt, that risk is likely due to the fact that window-seat occupants are less likely to move around during the flight. “There is nothing magical about sitting in the window seat. It’s just that you move less,” he says.
Guyatt says the research review also found no evidence that sitting in the cramped coach cabin carries a higher risk of clots than sitting in business or first class. “We found no support for ‘economy class syndrome,’” he says.
The panel also found little support for the belief that drinking lots of water and avoiding alcohol can keep clots from forming. There are good reasons to stay hydrated at 30,000 feet, but preventing DVT isn’t one of them. Still, drinking enough liquids does force you get up to use the bathroom, which isn’t a bad thing.
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The factors that did seem to be linked to a slightly higher risk of developing clots included medical issues such as being an active cancer patient, having circulation disorders, having had a recent surgery or broken bone, being obese, having limited mobility and having had previous blood clots. Pregnant women and those taking birth control pills may also be more prone to blood clots since they tend to have hormone levels that may promote the condition.
Not all of these groups are at equal risk, however, and Guyatt considers cancer patients and those with circulatory disorders to be the most vulnerable, and advises them to discuss with their doctors whether compression stockings, which can promote circulation in the legs, or anti-clotting drugs are worth using on flights lasting longer than two hours. So far, more studies have documented the benefits of the stockings than they have the anti-clotting agents.
For anyone in the higher risk groups, including women who are pregnant or on the pill, getting up and walking around periodically is not a bad idea. You can also flex and extend your ankles while in your seat, in order to get the calf muscles moving. And that goes for any situation in which you’ll be sitting for long stretches, whether it’s on a plane, train, bus, in a car or at your office desk.
So, despite the nickname “economy class syndrome,” the panel concludes that simply flying coach isn’t as important as your medical history before you board the plane — at least when it comes to blood clots. For healthy people who don’t fall into the high-risk categories, but still fear the risk of clots, Guyatt says, “the most important message is to forget about it.”
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Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.