Long‐haul flights and deep vein thrombosis: a significant risk only when additional factors are also present

Abstract

Summary. To address the association between travel and deep vein thrombosis (DVT) we examined the risk factors for DVT in 568 consecutive patients with suspected DVT attending King's College Hospital in London. No significant link between DVT and long-haul travel was demonstrable in this cohort, with an odds ratio of 1AE3 (CI 0AE6-2AE8). Risk of DVT was only increased in long-haul travellers if one or more additional risk factors were present, with an odds ratio of 3AE0 (CI 1AE1-8AE2). Such individuals may benefit from prophylactic measures to minimize risk.Keywords: deep vein thrombosis, airline flights, long-haul travel, risk factors, thromboprophylaxis.The link between travel and venous thrombo-embolism (VTE) remains a contentious one (Cruickshank et al, 1988;Hirsh & O'Donnell, 2001). Two previous French casecontrol studies provided evidence for the link between travel and venous thrombosis, with odds ratios of 4AE0 (Ferrari et al, 1999) and 2AE3 (Samama, 2000), respectively, in subjects undertaking long-distance travel by air and ground transportation. A further Dutch study, however, failed to show a relationship between venous thrombosis and travel (Kraaijenhagen et al, 2000). This case-control study used subjects presenting with similar symptoms in whom venous thrombosis was excluded as controls. For air travel the odds ratio (OR) and 95% confidence interval (CI) was 1AE0 (CI 0AE3-1AE4) and for any travel was 0AE7 (CI 0AE3-1AE4). Of note, only 17 of all 788 (2AE2%) participants and 4 of 186 (2AE2%) patients with confirmed DVT had a recent history of plane travel. The debate regarding flight-related risk was reopened by a recently published randomized trial which suggested that symptomless DVT might occur in up to 10% subjects following long-haul flights (Scurr et al, 2001). To address the association between travel and thrombosis we examined the risk factors for DVT in our patient population. PATIENTS AND METHODSWe prospectively determined risk factors for VTE in a cohort of 568 consecutive outpatients with clinically suspected DVT attending the DVT Clinic at King's College Hospital in south London. Referrals originated from the hospital's emergency department as well as primary care. Camberwell has an ethnically diverse population and is not located in close proximity to an airport. A medical history was taken at presentation using a standardized proforma with questions regarding travel and known risk factors for VTE comprising hormonal therapies, surgery, malignancy, immobilization, pregnancy, obesity, previous thrombosis and significant family history. A full travel history was taken and details recorded of air or surface journeys of more than 3-h duration in the preceding 4 weeks. In view of the ongoing debate regarding the relevance of short periods of travel, we also selected those subjects who undertook longhaul flights (greater than 8 h) for detailed study. The diagnosis of DVT was confirmed using duplex ultrasonography. We calculated the OR and CI for each subgroup. RESULTSFive hundred and sixty-e...

Effect of leg exercises on popliteal venous blood flow during prolonged immobility of seated subjects: implications for prevention of travel‐related deep vein thrombosis

“…In 1954 Homans reported a case of DVT that occurred in a physician after a 14-h flight, thereby associating VTE and longterm immobility from confined seating with air travel [2]. Studies have shown that asymptomatic lower limb DVT may arise in up to 10% of long-distance travelers depending on patient baseline risk of VTE [3,4], and that 4-20% of patients presenting with VTE have traveled within a few weeks prior to the event [5][6][7][8].…”

Hypercoagulability: Too Many Tests, Too Much Conflicting Data

“…27 Still, controlled studies have conflicting results on the magnitude of the risks (some even showing no risk increase at all), and it is unclear which factors contribute to risk. [28][29][30][31] In 2002, a large research project initiated by the World Health Organization (WHO) was launched to further elucidate these issues. The project is aptly named the WRIGHT study (WHO Research into Global Hazards of Travel).…”

Relation between Air Travel and Venous Thromboembolism

“…Nonetheless, the number of those who had not had a flight but had prolonged road or rail travel was higher; 77% of the cases (26) . In fact, the majority of these case controlled studies have found no link between travel, in general, and the development of VTE (6,24,34,44,57,58,64,82) . A descriptive study on the rate of occurrence of fatal PE estimated the rate at 0.5 per million and 1.3 per million occurring among travelers taking flights of more than 3 hours and more than 8 hours, respectively (58) .…”

“…If the condition has to be associated with travel, it must have occurred up to eight weeks after the travel (46) . In eleven case controlled studies, it has been reported that the risk of VTE cases related to travel is more evident in individuals with preexisting risk factors (6,19,24,26,34,44,51,57,58,64,82) . In most of these studies, traveling for at least three hours was associated with increased risk of thrombosis.…”