CANBERRA, Australia (Reuters) --Long-haul air travel does increase the chance of a person developing deep vein thrombosis (DVT).
However, the risk of dying in a car remains 100 times greater, according to an Australian study.
The study, conducted by the Australian Department of Health and Aging, found there was a small but heightened risk of developing DVT -- or so-called "economy class syndrome" - in the two weeks after a long distance flight.
DVT involves the formation of blood clots, potentially up to a foot (30 cm) in length, which can cause death if they invade the lungs or brain.
"The report showed that normally healthy people were at very low risk of DVT after long-haul flights while passengers with conditions such as cardiovascular disease, obesity, cancer or who are pregnant, would be at slightly greater risk," Australia's chief medical officer, John Horvath, said in a statement.
Horvath said the study, based on anonymous data about passenger arrivals and hospital admissions in Western Australia state, found a 12 percent increase in the background risk of suffering from DVT after traveling on one long flight per year.
"For an average middle-aged traveler, this means DVT would occur only once in 40,000 flights, with a death about once in two million flights," he said. "For young people the average risk would be much smaller."
He concluded that the annual risk of dying in a car accident was 100 times greater than the extra risk of dying from complications of DVT after a long-haul flight.
But he said airlines and prospective passengers should be alerted to the findings of the study that provided a significant contribution to public health information and policy development.
During recent court action victims have blamed cramped aircraft cabins for their blood clots and argued that airlines have known of the risks for years but failed to warn people.
But a British court agreed with the airlines, which claimed DVT was not an accident so if a passenger developed with the condition on a routine flight the carrier cannot be blamed.
DVT made international headlines and airlines came under pressure to do more to prevent the condition after a 28-year-old British woman died from the condition about three years ago after a 20-hour flight from Australia to London.
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