World Health Organisation Study

Background

The Problem

In the early 2000s there was much publicity about the possible link between long-haul air travel and deadly blood clots. Reports of passengers developing clots after long flights were mounting since media coverage of the death of a young woman from a blood clot shortly after she disembarked from a flight from Australia to London 30 September 2000.

Passengers on long-haul flights can be subjected to long periods of inactivity, a cramped seated position and a tendency to become dehydrated. These conditions can cause a number of circulatory problems, ranging from swollen ankles and tired aching legs, to more serious medical conditions such as deep vein thrombosis.

Deep vein thrombosis is a potentially fatal condition which occurs in hospital patients who are immobilised for long lengths of time as well as in passengers on long-haul flights or long-distance coach rides. The probability of thrombosis increases in individuals with underlying coagulation disturbances including clotting factor abnormalities and hyper-viscosity syndromes. Exercises that stimulate the deep venous plexus of the calf especially in the situations noted above may reduce the incidence of deep vein thrombosis.

In March 2001, the World Health Organisation medical experts and airline representatives meeting in Switzerland, said there is a likely link between long-haul flights and deep vein thrombosis.

After nearly 50 years of mass air transit, it was only then that the problem would be thoroughly investigated and in April 2002, the World Health Organisation launched a four-year study into the possible links between air travel and deep vein thrombosis.

In 2007 the World Health Organisation published its findings on the comprehensive study (the WRIGHT) project, whose objectives were to confirm that the risk of venous thromboembolism (VTE) is increased by air travel and to determine the magnitude of risk, the effect of other factors on the risk and to study the effect of preventive measures on risk.

World Health Organisation

Conclusion

‘The findings of the epidemiological studies indicated that the risk of VTE approximately doubles after a long-haul flight (>4 hours). The data also showed that this increased risk applied to other forms of travel (such as car, bus or train) where travellers are exposed to prolonged seated immobility. The risk increased with the duration of the travel, and with multiple flights within a short period.

The findings of Phase 1 of the WRIGHT project demonstrated that the increased risk of VTE observed in long-haul travellers is due mainly to prolonged immobility.