A new study has found that as much as 10 per cent of travellers may develop deep vein thrombosis (DVT) on long haul flights.

The finding came from a study, carried out by Lister Hospital in London, of the effectiveness of elastic compression stockings in preventing DVT during extended air travel.

Dr John H. Scurr and his colleagues studied 89 men and 142 women, who were over 50 years of age and with no previous history of thromboembolic problems. Participants were randomised to wear below the knee graduated, elastic compression stockings or no stockings during flights that lasted longer than eight hours.

The study participants were evaluated, using ultrasound and blood analyses, within 48 hours of returning to the UK.

None of the 115 subjects who wore the compression stockings developed DVT whereas 10 per cent of those who did not wear the stockings developed symptomless DVT in the calf.

However, four participants with varicose veins who wore the compression stockings developed super ficial thrombophlebitis (Lancet, 2001; 357: 1485-9).

In an editorial accompanying the study report, doctors from McMaster University in Hamilton, Ontario in Canada, disputed the findings, questioning the 100 per cent risk reduction figure, and noting that the risk of DVT found in this study was anywhere from 40 to 150 times greater than seen in previous studies (Lancet, 2001; 357: 1461-2).