THE incidence of deep vein thrombosis (DVT) – dangerous blood clotting – among passengers flying on long-haul routes appears to be much lower than earlier estimates, according to the largest DVT survey of air travellers.
The survey also reinforced claims that passengers in economy class seats were no more likely to develop DVT than those in more roomy business class cabins.
And while further research is needed to confirm the survey’s findings, it suggested that in-flight exercises such as stretching toes and drinking plenty of water make no difference to whether a passenger suffers from DVT.
Professor Barry Jacobson, head of the surgical research unit at the University of Witwatersrand, Johannesburg, and organiser of the study, said his research indicated less than 1% of passengers face the risk of developing DVT. Earlier studies suggested a much higher rate of between three and 10%.
Prof Jacobson said his survey last year, which involved blood sampling and clinical tests before and after flying, was the largest carried out into DVT. But he acknowledged that a much larger sample would need to be tested to ascertain the exact incidence of DVT.
“Our sample size was statistically drawn up to see whether people in business class seats were any more or less likely to develop DVT than those in economy class seats,’’ he said.”
The research showed there was no difference between the two.
“But it also suggested a relatively low incidence of DVT of 1% maximum, although another study involving a larger sample will be needed to establish the exact rate.’’
The study was partly paid for by drugs companies developing blood-thinning drugs and involved the support of South African Airways, which gave 5,000 free air miles to passengers who volunteered to take part.
The suggestion of a lower-than-expected DVT rate will be welcomed by the airlines, which face legal action from the families of passengers who have died from blood clotting after long-haul flights.
Recently relatives of DVT victims seeking damages failed to overturn a British court ruling that blocked their case.
Prof Jacobson’s study found a relatively high level after flying of the D-dimer protein, which is used as a marker for small blood clots. He said the level was raised significantly in around 10% of the passengers.
He said more research would have to be done to establish any link between the protein and fatal DVT clots.
“The mass hysteria is not realistic, but something is going on,’’ Prof Jacobson said. – © Telegraph Group Ltd, London