Since the early days of air travel, the possibility of developing dangerous blood clots during flights has been a concern for travelers. Over time, wearing compression socks has become a frequently suggested preventative measure. But are compression socks truly essential for flying, or is it just another travel myth?
According to Dr. Joshua Beckman, a vascular medicine expert at UT Southwestern Medical Center, using compression socks is “perfectly fine.” However, he points out that scientific evidence doesn’t definitively quantify their benefits for air travelers. This raises the question: should compression socks be a mandatory item in your carry-on, or is their effectiveness overstated?
Compression socks, also known as graduated compression stockings, are designed to apply pressure that is strongest at the ankle and gradually decreases up the leg. This compression is intended to aid blood circulation by encouraging blood flow from the legs back to the heart.
Deep vein thrombosis (DVT), a condition where blood clots form in large veins, typically in the legs, affected an estimated 666,000 people in the U.S. in 2020, according to the American Heart Association. Pulmonary embolism (PE), a related condition where a clot travels to the lungs, led to 432,000 hospitalizations. Together, DVT and PE constitute venous thromboembolism (VTE), which was linked to nearly 81,000 deaths in 2021.
Symptoms of DVT can include leg pain, swelling, and skin warmth, while PE may manifest as shortness of breath, coughing, and chest pain.
Research indicates that long-haul flights can increase the likelihood of VTE by 1.5 to four times, as highlighted in a 2021 Cochrane Database of Systematic Reviews study.
Despite this increased risk, it’s important to note that dangerous blood clots remain relatively uncommon in air travel. A 2007 study in the Journal of Internal Medicine estimated approximately 4.8 cases of severe pulmonary embolism per million flights exceeding 12 hours. The risk of DVT within four weeks after a flight of at least four hours was estimated at 1 in 4,600 flights.
Dr. Eri Fukaya, a vascular medicine specialist at Stanford University, explains that flying can create a confluence of factors conducive to clot formation. However, she emphasizes that individual risk factors play a more significant role.
Factors such as older age, smoking, obesity, and a family history of blood clots elevate VTE risk. Individuals with a history of clots, recent cancer treatment, or estrogen use are also at increased risk.
Dr. Fukaya uses an analogy of a bucket to illustrate risk accumulation. Individuals with pre-existing risk factors have a fuller “bucket,” making them more susceptible to the additional risk posed by air travel. For those with already high risk levels, flying might be the trigger that causes the “bucket to overflow.”
Prolonged immobility in cramped airplane seats is a contributing factor. Furthermore, passengers may reduce their fluid intake to avoid frequent bathroom trips, potentially leading to dehydration, which can thicken the blood.
However, Dr. Beckman stresses that the risk of developing severe blood clots solely due to flying is so low that conducting definitive studies is challenging.
He cites a 2022 study in the American Journal of Obstetrics and Gynecology: Maternal-Fetal Medicine, which examined VTE risk in pregnant and postpartum women, a high-risk group. While women who flew had a slightly elevated risk compared to non-flyers, the difference was minimal – 0.07% versus 0.05%, respectively.
These small numbers highlight the difficulty in definitively proving the effectiveness of compression socks in preventing blood clots in air travelers. “If the risk is really low, and you go from really low to really, really low, you can’t have enough people in a study to actually figure it out,” Beckman explains.
The Cochrane review, analyzing data from 2,918 participants across 12 clinical trials, found strong evidence that compression stockings reduce the risk of asymptomatic DVT during flights longer than four hours. However, the review couldn’t draw conclusions about the impact on death, pulmonary embolism, or symptomatic DVT due to the absence of these events in the trials.
The American Society of Hematology guidelines do not recommend compression socks for low-risk travelers on short flights. They suggest considering them for longer flights only for individuals at high risk of blood clots.
Hospital studies have demonstrated the effectiveness of compression socks in preventing blood clots in post-surgical patients, according to Dr. Beckman. However, their benefit for non-surgical, bedridden patients is less conclusive. He argues that if establishing a clear benefit is difficult even for hospitalized, ill patients, it’s even more challenging to prove their effectiveness for healthy, mobile individuals traveling by plane or car.
Nevertheless, Dr. Beckman emphasizes that if a doctor recommends compression socks for any reason, it’s crucial to follow that advice.
For travelers concerned about blood clots, Dr. Beckman’s primary recommendation is to “get up and walk every couple of hours. Drink lots of water.”
Dr. Fukaya concurs, adding that seated passengers should perform simple exercises like flexing calf muscles and rotating ankles in large circles, both clockwise and counterclockwise. She also suggests removing shoes and wiggling toes to further stimulate blood flow.
If you already use compression socks and find them comfortable, there’s no need to discard them.
Dr. Fukaya, despite the limited definitive scientific evidence for air travel specifically, is a personal advocate for compression socks and wears them regularly.
She notes that compression therapy has historical roots and that compression socks can stimulate calf muscles during movement and help reduce swelling.
“I wear them almost every day,” Fukaya states, explaining that her personal experience led her to believe in their benefits, noting that “my legs feel a lot better wearing them.”
While individuals with peripheral artery disease and poor circulation should use compression socks cautiously, Dr. Fukaya encourages others to experiment and find what works best for them.
The market offers a wide variety of compression socks, including those marketed for athletes and medical-grade options. Medical-grade socks are categorized by pressure levels measured in millimeters of mercury, but Dr. Fukaya considers these ratings less critical. She points out that actual pressure can vary based on leg size and that sock ratings lack standardization.
She likens choosing compression levels to ordering food spice levels, suggesting starting with a “medium” compression level and adjusting based on comfort.
Dr. Fukaya even suggests a practical test: “You could wear it on one leg and not the other and see if one leg feels better than the other at the end of travel.” She recommends knee-high socks over thigh-high versions but cautions against rolling down knee-high socks if they are too long, as this can create a tourniquet effect.
Dr. Beckman concludes that compression socks are acceptable for those who like them. However, he emphasizes that focusing on general healthy travel habits, such as staying hydrated and moving around, is more crucial for safe travel. He also humorously points out that sunscreen might be a more essential item to remember for overall health protection.
Ultimately, while compression socks might offer a slight risk reduction for some travelers, particularly those at higher risk of blood clots, simple measures like staying hydrated and moving regularly during flights remain the most broadly recommended and evidence-based strategies for minimizing VTE risk.
