Their study finds even flying in business class can put people at increased risk of developing dangerous blood clots during long flights.
The link between blood clots (venous thromboembolism) and prolonged sitting was first described during World War II, when doctors noticed a rise in fatal pulmonary embolisms among people who slept in deck chairs in London air raid shelters. The association was further described in 1954, when blood clots were first identified among air and car travelers. It wasn't until 1977, however, that the term "economy class syndrome" was coined. The theory was that sitting in the cramped seats typical of the economy class section of an aircraft made it harder for people to move around during long flights, thus making it easier for blood clots to develop.
This study looked at 878 air travelers who completed at least 10 hours of air travel over six weeks. All took flights lasting at least four hours. The mean total duration of air travel during the study was 39 hours.
Participants underwent blood tests before and after the study to check for a marker of blood clotting. Results showed nine out of the 878 developed venous thromboembolism, four of whom also had a pulmonary embolism. Among the group, two passengers sat exclusively in business class.
Preventative measures were also common among the affected group: five reported using aspirin and four wore compression stockings. While several did have pre-existing conditions putting them at increased risk for blood clots, others had no risk factors at all.
Thus researchers conclude that according to their study venous thromboembolism is a potentially important health problem to many long distance air travelers, including those without recognized risk factors.