Experts refer to it as "economy class syndrome," yet it can affect anyone in any class of aircraft. Deep vein thrombosis (DVT) occurs when blood clots in one or more veins.
It can happen at any moment, but long-haul flight passengers are at a higher risk since they sit for extended periods of time, according to Dr. Pinakin V. Parekh, a consultant cardiologist at Singapore's Harley Street Heart and Vascular Centre.
While the risk of DVT is often associated with air travel, it's important to note that prolonged periods of immobility in any setting can increase the likelihood of developing blood clots. This includes long car rides, train journeys, or even extended periods of sitting at a desk. The key factor is the lack of movement, which can impede blood circulation and potentially lead to clot formation. Awareness of this risk in various situations can help individuals take preventive measures, regardless of their mode of transportation or daily activities.
"Theoretically people who are in better classes of air travel — business class, first class — have more space to move about, stretch their legs," according to him. "So it's all about real estate in the plane."
However, Parekh is quick to point out that so-called "economy class syndrome" does not discriminate based on where you seat or how frequently a person flies.
"I've had patients who travel even in business class also develop DVT," according to him. Further, "it can be the only flight of your life, if you decide not to move."
What raises the hazards.
Deep vein thrombosis commonly develops in the legs. According to the Mayo Clinic, symptoms include discomfort, swelling, skin color changes, and a feeling of warmth, but other patients show no signs at all.
According to the medical facility, people who are obese, over the age of 60, use birth control pills or hormone replacement therapy, or smoke are more likely to develop deep vein thrombosis.
Recent studies have also highlighted additional risk factors for DVT that are often overlooked. Dehydration, for instance, can significantly increase the risk of blood clot formation. When the body is dehydrated, blood becomes more concentrated and viscous, making it more prone to clotting. This is particularly relevant during air travel, as the low humidity environment in aircraft cabins can lead to faster dehydration. Additionally, certain genetic factors can predispose individuals to a higher risk of DVT. Mutations in genes related to blood clotting, such as Factor V Leiden, can increase the likelihood of developing blood clots, even in otherwise healthy individuals.
However, flying is not without risks, according to Parekh.
"For one in every 5,000 flights that are flown, one patient ... can develop DVT just by the risk of air travel," he claimed.
Long-haul flight passengers are at higher risk, although deep vein thrombosis can occur on shorter journeys, he added.
"People used to define long haul flights as eight hours," he informed me, "but there's some data to suggest that even four hours now is considered long enough."
Alok Tapadia, a 52-year-old former banker, claimed he acquired deep vein thrombosis during a four-hour journey from Singapore to Hong Kong.
He stated that he plays badminton three times a week, so he recognized something was amiss when he grew breathless while walking up a flight of stairs after arriving in Hong Kong.
"One of the escalators had stopped working," he explained, so he took the stairs. "I had to stop for a while, and I was wondering what's happened to me."
It wasn't until he returned to Singapore, still breathless and with an elevated heart rate, that he sought medical attention.
He said physicians told him a clot had gone to the pulmonary artery, which connects his heart and lungs.
He claimed his initial scan revealed an enlarged heart, which happens when the heart pumps too hard. According to Tapadia, a second scan resulted in his immediate admission to the hospital's intensive care unit.
The physicians discovered that he had been "massively" short on oxygen and that his lungs were entirely obstructed, he added.
Doctors described the scenario as "critical, because there was so much pressure on the heart that it could have, you know, gone into an arrest or gone into a more critical stage any moment," Tapadia stated.
The case of Alok Tapadia underscores the importance of prompt medical attention when experiencing unusual symptoms after travel. Many individuals may dismiss shortness of breath or fatigue as mere jet lag or travel exhaustion, potentially delaying crucial diagnosis and treatment. Medical professionals emphasize that any persistent or concerning symptoms following a flight, particularly breathlessness, chest pain, or swelling in the legs, should be evaluated immediately. Early detection and intervention in cases of DVT or pulmonary embolism can significantly improve outcomes and prevent life-threatening complications.
Blood thinners did not dissolve the clot quickly enough, he claimed. So his physicians eventually turned to cardiac catheterization, which included threading a catheter through his blood veins near his heart to destroy the blood clot from the inside, according to Tapadia.
Tips to Reduce DVT
According to the Mayo Clinic, deep vein thrombosis can progress to pulmonary embolism, a potentially fatal consequence in which a blood clot breaks free and becomes lodged in a blood vessel in the lung.
According to Parekh, when a clot enters the lungs, symptoms such as dyspnea and chest pains may occur. The danger of deep vein thrombosis cannot be entirely eliminated. However, there are measures to limit the risks of flying, he argues.
The Mayo Clinic recommends drinking plenty of water, standing and strolling around the plane during the flight, rotating your ankles while sitting, and wearing support stockings.
Parekh offers a simple recommendation for flyers: take an aisle seat.
The technique "encourages you to walk up and start walking much more easily because when you're all the way inside the row, you're always worried you're disturbing the guy next to you," Parekh writes.
In addition to these preventive measures, some airlines have begun implementing innovative approaches to reduce the risk of DVT among passengers. Some long-haul flights now feature in-flight exercise programs, where cabin crew lead passengers through simple stretching routines at regular intervals. Other airlines have introduced seat designs that encourage subtle movements and better circulation, even when passengers remain seated. While these initiatives are promising, experts stress that they should complement, not replace, individual preventive actions such as regular movement and hydration during flights.
More than a year later, Tapadia said he's back to his typical living pattern, which includes traveling and badminton, though he's adjusted some of his travel routines, beginning with the airport.
He now walks through the airport rather than using the travelator, he explained. Furthermore, he wanders up and down the aisles while flying, he explained. He recommends travelers to monitor their health and any warning indications.
"This kind of an episode really shakes you up," he told me.
