Pulmonary embolism after a long-haul flight

The relation between long-haul flights (LHF) and venous thromboembolic disease is well established. Nonetheless, the incidence of pulmonary embolisms after these flights is probably underestimated because of the difficulties in case ascertainment. Reunion Island appears to present the ideal geographic conditions for accurately assessing this incidence. We aimed to assess the incidence of pulmonary embolisms in people who had recently taken a LHF to Reunion Island. We conducted a retrospective multi-center descriptive study and included all cases of pulmonary embolisms diagnosed between January 1, 2015, and January 30, 2017 (according to the hospitals' discharge summary database) in the island's four public hospitals within 30 days after taking an LHF to Reunion. We took different delays of diagnosis to calculate the incidence. We have considered the time to diagnosis at 1 month as significant according to the time applied in the Geneva score for risk factors. The study included 45 patients landing on Reunion over a 2-year period. The total number of passengers arriving by LHF during this period was 1,223,001. The incidence of pulmonary embolism after an LHF was thus calculated at 36.8 per million travelers at 1 month. The incidence for PE diagnosed, after 15 days was 29.4 per million travelers, and after 7 days, it was 21.9 per million travelers. The male/female ratio was 0.67. The mean interval between the flight and symptom onset was 7 days. In our population, the incidence of pulmonary embolisms after LHFs in our study is clearly higher than that reported in the literature (36.8 vs 4.8). Our exhaustive data collection probably explains this difference. A case-control study appears necessary to analyze the risk factors for pulmonary embolism after a LHF.