Issue date: 03 December 2002

Scientists at the University of the West of England have carried out a study which analyses the risk to long-haul air travellers of suffering from pulmonary embolism (PE) and venous thromboembolism (deep vein thrombosis - DVT).

Their study, published in the American journal, Aviation, Space and Environmental Medicine in December concludes that the risk of long haul air passengers suffering from these conditions is currently overstated.

Epidemiologists Dr Derek Pheby and Dr Ben Codling of the University of the West of England say that in the general population PE tends to be under diagnosed as a cause of death. Dr Pheby says, “We set out to establish a clearer picture of the role of PE in mortality in the general population and thereby to establish the level of risk of fatal PE among long-haul passengers arriving in the UK.

“Working with data from Gloucester Royal Hospital Histology Database, we re-examined nearly 4000 post mortem examinations. The age distribution in Gloucester was suitable for this study, as it is very similar to that of England and Wales as a whole. From this data we worked out age-specific mortality rates for PE for the whole country. Using civil aviation authority data we were able to calculate the expected number of deaths from these conditions in long haul passengers arriving in the UK.”

Derek Pheby says, “Our review of numbers of deaths involving PE in Gloucester suggest that they are much more common in the general population than is generally perceived. Based on our calculations we estimate that about 6.55 deaths would occur annually among long-haul arrivals in the UK. However information currently published about the number of deaths actually occurring in passengers are only estimates, although our figure does lie within the range of those estimates. It is also consistent with the observation of the House of Lords Select Committee on Science and Technology that states: ‘If there is an increased risk of DVT solely from flying, it is small.’*

“Some deaths are bound to occur on flights simply because of the number of people and the length of time involved in flying, but there is no evidence to suggest a significant excess over expected numbers. Clearly there are risk factors present in any long journey which can predispose to the development of DVT. There is no evidence of flight-associated increase in risk factors for PE, and indeed in our view these appear to be no greater than is found in the general population.”

“This study has demonstrated that PE is very much more frequently implicated as a cause of death in the general population than is generally realised. The frequency of deaths among long-haul air travellers is not markedly greater than among comparable populations and PE as a cause of death is relatively rare. Nevertheless there are risk factors for DVT associated with long distance travel.”

The researchers say they would still advise sensible precautions particularly for those who may have a predisposition to DVT, “In our view, those going on a long-haul flight should avoid leg discomfort while seated, and avoid alcohol and caffeine-containing drinks, before and during flight. They should not take sleeping pills and should have only short periods of sleep. People in whom specific risk factors have been identified should take professional medical advice.”


Editor’s notes

*House of Lords Select Committee on Science and Technology Fifth Report. London: House of Lords; 2000

Pulmonary Embolism at Autopsy in a Normal Population: Implications for Air Travel Fatalities by D F H Pheby and B W Codling is published in Aviation, Space and Environmental Medicine, Vol. 73, no. 12 pages 1208-1214.

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