WHO Research into global hazards of travel (WRIGHT) project
Final report of Phase I
The objectives of the WRIGHT (WHO Research Into Global Hazards of Travel) project 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.
To address these objectives, several studies were performed during Phase I of the WRIGHT project. Additional proposed studies related to the effect of preventive interventions were deferred to Phase II.
The findings of the epidemiological studies indicate that the risk of VTE approximately doubles after a long-haul flight (>4 hours) and also with other forms of travel where travellers are exposed to prolonged seated immobility. The risk increases with the duration of the travel and with multiple flights within a short period.
The risk also increases significantly in the presence of other known risk factors of VTE. The risk factors identified as contributors to the increased risk of travel-related VTE were obesity, extremes of height, use of oral contraceptives and the presence of prothrombotic blood abnormalities.
The absolute risk of VTE per more than four-hour flight, in a cohort of healthy individuals was 1 in 6000.