Venous thromboembolism in passengers following a 12-h flight: a case-control study

There has recently been great interest in the possible relationship between air travel and venous thromboembolism (VTE). Based on a case-control survey, we measured the frequency of VTE, associated risk factors (RFs), and factors influencing the onset of pulmonary embolism (PE) or deep vein thrombosis (DVT).

The study was conducted over 1 yr. A questionnaire was sent to physicians. Patients with a diagnosis of VTE were included, provided they had traveled from France to Reunion Island.

Over 46 cases, 33 patients showed DVT and 13 PE. RFs for VTE were present in 38 patients (82%). On comparing RFs between study and control groups, we found no differences in age, gender, alcohol, sleep-inducing drug consumption, seat allocation, or estroprogestative treatment. RFs were significantly higher in the VTE group at p < 0.005: history of previous VTE (OR 63.3), recent trauma (OR 13.6), presence of varicose veins (OR 10), obesity (OR 9.6), immobility during flight (9.3), and cardiac disease (OR 8.9). For patients with DVT or PE, no differences were observed in comparing RFs. The PE group was older and mortality occurred only in this group. The number of displacements during flight (p < 0.009) and complete immobility (p < 0.001) were strongly related with onset of PE. Delay of symptoms was less than 24 h in 69% of PE cases compared with 21% of DVT cases (p < 0.004).

Long-duration air travel VTE is associated with other underlying thromboembolic RFs. Low mobility during flight is a striking modifiable RF of developing PE. Travelers with RFs for VTE should be advised to increase their mobility.