Since the dawn of air travel, the concern about blood clots during flights has been a topic of discussion. Often, this concern comes with recommendations to use Travel Support Hose, also known as compression socks.
However, the necessity of packing travel support hose isn’t as straightforward as it might seem.
According to Dr. Joshua Beckman, a vascular medicine expert at UT Southwestern Medical Center, “It’s perfectly fine to use them.” However, he points out that scientific evidence doesn’t definitively quantify the extent to which travel support hose benefit travelers.
Travel support hose, or graduated compression stockings, apply pressure that is strongest at the ankles and gradually decreases up the leg. This compression is designed to aid blood circulation, encouraging blood flow from the legs back to the heart.
In the U.S., it’s estimated that 666,000 individuals were hospitalized for deep vein thrombosis (DVT) in 2020, based on recent data from the American Heart Association. DVT occurs when a blood clot develops in a major vein, typically in the leg. Furthermore, 432,000 people were hospitalized for pulmonary embolism, a condition where a clot travels to the lungs. Collectively, these conditions are known as venous thromboembolism, or VTE, and were linked to nearly 81,000 deaths in 2021.
Symptoms of DVT may include leg pain, swelling, or skin warmth. Pulmonary embolism symptoms can manifest as shortness of breath, coughing, and chest discomfort.
Research indicates that long-distance flights can increase the likelihood of VTE by 1.5 to 4 times, as noted in a Cochrane Database of Systematic Reviews study.
Despite this increased risk, it’s important to recognize that serious blood clots remain uncommon. 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 of a flight lasting at least four hours was found to be 1 in 4,600 flights.
Dr. Eri Fukaya, a vascular medicine specialist at Stanford University, suggests that air travel can create a confluence of factors that might promote clot formation. However, she emphasizes that other pre-existing conditions are more significant.
Individuals at higher VTE risk include older adults, smokers, those with obesity, or those with a family history of blood clots. This also applies to individuals with a prior history of clots, recent cancer treatment, or estrogen use.
Dr. Fukaya uses an analogy of a bucket filling with water to explain risk factors. People with more risk factors have a fuller bucket, making them more susceptible to overflow – in this case, a blood clot – when exposed to triggers like air travel.
Prolonged immobility, common during long flights in confined spaces, elevates risk. Additionally, reduced hydration among air travelers, who may limit fluid intake to avoid frequent bathroom breaks, can thicken the blood, further contributing to the risk.
However, Dr. Beckman reiterates that the risk of developing severe blood clots solely due to flying is still very low, making it difficult to study definitively.
He mentions a 2022 study in the American Journal of Obstetrics and Gynecology: Maternal-Fetal Medicine focusing on pregnant and postpartum women, a high-risk group for VTE. While the study showed a slightly higher risk of VTE in women who flew compared to those who didn’t (0.07% vs. 0.05%), Dr. Beckman emphasizes the difference was “very tiny.”
These small numbers illustrate the challenge in determining whether travel support hose effectively prevent 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 analyzed data from 2,918 participants across 12 clinical trials. It found strong evidence that travel support hose reduce the risk of asymptomatic DVT during flights exceeding four hours. However, the review couldn’t draw conclusions about the impact on death risk, pulmonary embolism, or symptomatic DVT due to the absence of these outcomes in the trials.
Guidelines from the American Society of Hematology do not recommend travel support hose for low-risk individuals on short flights. They suggest considering them for longer flights only for those at higher risk of blood clots.
Studies in hospital settings have demonstrated the effectiveness of compression socks in preventing blood clots in post-surgical patients, according to Dr. Beckman. However, the benefits are less clear for non-surgical patients on bed rest. He argues that if establishing a clear benefit is challenging even for hospitalized, bedridden individuals, demonstrating the effectiveness for healthy, mobile travelers is even more difficult.
Nevertheless, Dr. Beckman stresses that if a doctor recommends travel support hose for any reason, it’s crucial to follow that advice.
For travelers concerned about blood clots, Dr. Beckman’s primary advice is to “get up and walk every couple of hours. Drink lots of water.”
Dr. Fukaya adds to this, suggesting seated exercises such as flexing calf muscles and rotating ankles in large circles, both clockwise and counterclockwise. She also recommends removing shoes to wiggle toes, as these movements promote blood circulation.
And for those already using and comfortable with travel support hose? There’s no need to discard them.
Dr. Fukaya, while acknowledging the limited definitive proof of benefit for flight-related clots specifically, is personally a proponent of travel support hose and wears them regularly.
She notes compression’s long history, dating back to ancient times, and explains that travel support hose stimulate calf muscles during movement and can help minimize swelling.
“I wear them almost every day,” Dr. Fukaya states, explaining she started to better understand her patients’ experiences and found her legs felt better with them.
Individuals with poor circulation from peripheral artery disease should exercise caution with travel support hose, Dr. Fukaya advises. However, for most others, experimenting to find what works best is reasonable.
The market offers a wide array of travel support hose, from those marketed to athletes to medical-grade options. Medical-grade socks are categorized by pressure in millimeters of mercury, but Dr. Fukaya finds these ratings less critical. She points out pressure varies with leg size, and rating standardization is lacking.
“It’s kind of like going to a restaurant and saying, ‘Do you want mild, medium or spicy?'” Fukaya analogizes, recommending starting with a medium compression level and adjusting based on comfort.
“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 suggests. Dr. Fukaya prefers knee-high versions over thigh-high ones. If knee-high socks are slightly too long, avoid rolling them down, as this can create a tourniquet effect.
Ultimately, both Dr. Beckman and Dr. Fukaya agree that travel support hose are acceptable for those who find them comfortable. However, for overall safe travel, Dr. Beckman emphasizes other priorities, like sunscreen.
“There are so many things that people have to think about” for health protection, he concludes. “It’s also important to get them to not have to think about things they don’t need to think about.”
