Flying, while a marvel of modern transportation, comes with its share of health concerns. Among these, the risk of blood clots during long journeys has been a persistent worry for travelers since the dawn of the jet age. Often, the advice to wear compression socks accompanies these warnings. But are compression socks truly essential for every traveler, or is the science more nuanced?
“Using compression socks is absolutely okay,” states Dr. Joshua Beckman, a vascular medicine expert at UT Southwestern Medical Center in Dallas. However, he points out that scientific evidence doesn’t definitively quantify their benefits for air travelers. This raises the question: how effective are compression socks, really, and for whom are they most beneficial?
Compression socks, also known as graduated compression stockings, are designed to apply pressure at the ankle, gradually decreasing as they move up the leg. This graduated compression is intended to aid blood circulation, encouraging blood flow from the legs back to the heart. This mechanism is particularly relevant when considering the risks associated with prolonged immobility during travel.
Deep vein thrombosis (DVT), a condition involving blood clot formation in a deep vein, often in the leg, affected an estimated 666,000 individuals in the U.S. in 2020 alone, according to the American Heart Association’s recent data. Pulmonary embolism (PE), a more serious condition where a clot travels to the lungs, hospitalized an additional 432,000 people. Collectively, these conditions, known as venous thromboembolism (VTE), contributed to nearly 81,000 deaths in 2021. Symptoms of DVT can include leg pain, swelling, and warmth to the touch, while PE may manifest as shortness of breath, coughing, and chest pain.
Long-haul flights are known to increase the likelihood of VTE by 1.5 to four times, according to a comprehensive review in the Cochrane Database of Systematic Reviews (2021 update). Despite this increased risk, it’s crucial to remember that the absolute risk of developing dangerous blood clots from flying remains low. A 2007 study in the Journal of Internal Medicine estimated only 4.8 cases of severe pulmonary embolism per million flights exceeding 12 hours. For flights longer than four hours, the risk of DVT within four weeks was approximately 1 in 4,600 flights.
Dr. Eri Fukaya, a vascular medicine specialist at Stanford University, emphasizes that flying can indeed create a “perfect storm” for clot formation. However, she highlights that pre-existing risk factors play a more significant role. Individuals who are older, smokers, obese, or have a family history of blood clots are at a higher baseline risk of VTE. Similarly, those with a history of clots, recent cancer treatment, or estrogen use also face elevated risk.
Dr. Fukaya uses the analogy of a bucket to illustrate risk accumulation. Individuals with multiple risk factors have a “bucket” that is already partially filled. Air travel, in this context, might be the factor that causes the “bucket” to overflow, triggering a blood clot. Immobility during long flights, coupled with dehydration from reduced water intake (to avoid frequent bathroom trips), further contributes to this risk by slowing blood flow and potentially thickening the blood.
Despite these risks, the relatively low incidence of flight-related blood clots makes definitive studies challenging, as Dr. Beckman points out. He cites a 2022 study in the American Journal of Obstetrics and Gynecology: Maternal-Fetal Medicine, focusing on pregnant and postpartum women—a high-risk group. While the study showed a slightly increased VTE risk for women who flew compared to non-flyers (0.07% vs. 0.05%), the difference was minimal. These minute risk differences underscore the difficulty in conclusively proving the effectiveness of compression socks in preventing blood clots in the general flying population. The risk is so low that demonstrating a statistically significant reduction with compression socks requires extremely large study groups.
A Cochrane review analyzed data from 2,918 participants across 12 trials. It found strong evidence that compression stockings reduce the risk of asymptomatic DVT during flights exceeding four hours. However, the review couldn’t draw conclusions about the impact on death, pulmonary embolism, or symptomatic DVT because these severe outcomes were not observed in the study participants.
Current guidelines from the American Society of Hematology do not generally recommend compression socks for low-risk travelers on short flights. For longer flights, they are suggested only for individuals identified as being at high risk of blood clots.
While studies in hospital settings demonstrate the effectiveness of compression socks in preventing blood clots post-surgery, their benefit for non-surgical patients on bed rest is less clear, according to Dr. Beckman. He argues that if establishing a clear benefit is difficult even for hospitalized, bedridden patients, proving efficacy for healthy, mobile travelers is even more challenging.
Nevertheless, both experts agree that if a physician recommends compression socks for an individual, those recommendations should be strictly followed. However, for general travelers concerned about blood clots, Dr. Beckman’s primary advice is straightforward: “Get up and walk every couple of hours. Drink plenty of water.”
Dr. Fukaya echoes this advice and adds simple exercises that can be performed while seated. She recommends flexing calf muscles and rotating ankles in large circles, in both directions. She also suggests removing shoes and wiggling toes to further promote blood circulation.
For those who already use and find comfort in compression socks, there’s no need to discard them. Dr. Fukaya, a personal advocate for compression socks, wears them regularly. She highlights their long history of use and their ability to stimulate calf muscles during movement and reduce swelling. “I wear them almost every day,” she shares, noting that her legs feel noticeably better when wearing them.
While compression socks are generally safe, Dr. Fukaya cautions individuals with peripheral artery disease and poor circulation to use them with care. For others, experimenting with different types to find what works best is encouraged. The market offers a wide range of compression socks, from athletic to medical-grade. Medical-grade socks are categorized by pressure levels (mmHg), but Dr. Fukaya finds these ratings less critical, as actual pressure varies with leg size and rating standards are not strictly regulated. She suggests a “mild, medium, or spicy” approach, recommending starting with a medium compression and adjusting based on comfort. Trying a sock on one leg only and comparing the feeling to the other leg after travel can also be a practical way to assess personal benefit. Knee-high socks are generally preferred over thigh-high versions, and it’s crucial not to roll down knee-high socks if they are slightly too long, as this can create a tourniquet effect.
In conclusion, while compression socks are harmless and may offer a degree of benefit, especially for high-risk individuals and those who find them comfortable, the most impactful measures for preventing blood clots during travel remain consistent: regular movement and adequate hydration. As Dr. Beckman aptly puts it, travelers have many health concerns to consider, and it’s important to focus on the most evidence-based and effective strategies for safe and healthy journeys. Perhaps, instead of solely relying on compression socks, focusing on staying active and hydrated during flights should be the primary focus for most travelers.
