Title: Venous thromboembolism in long-distance air travellers
Abstract: Authors' reply Sir—In response to Andrea Klauser and colleagues, we suggest that air traveller's thrombosis should only have been called economy class syndrome in the first place if it had been established that travelling in economy class was associated with an increased risk of venous thromboembolism compared with travelling in other classes. This was not the case, since the original report by Cruickshank and colleagues1Cruickshank SM Gorlin R Jennett B Air travel and thrombotic episodes: the economy class syndrome.Lancet. 1988; 2: 497-498Abstract PubMed Scopus (215) Google Scholar reported the details of three individuals with venous thromboembolism (VTE) associated with air travel, one of whom travelled in business class. Thus we advocate the neutral term air traveller's thrombosis or, more specifically, air-travel-related venous thrombo-embolism. The possibility that travellers in business class might have been at greater risk if they had been older was not the case in our series. The mean age of the 160 business-class passengers was 49·8 years, and that of the 718 economy-class passengers 48·9 years (difference 0·9 years, 95% CI –1·0 to 3·0, p=0·36). We concur with the view that the differential risk of VTE between business-class and economy-class travellers requires investigation, although such analysis would probably require a case-control approach owing to the large number of individuals needed for a clinical trial, as highlighted by Klauser and colleagues. The primary objective of the New Zealand Air Traveller's Thrombosis study was to determine the frequency of VTE in long-distance air travellers, not to compare the relative risk between short-haul and long-haul travellers, as suggested by John Miller. This latter issue has been studied by Lapostolle and colleagues,2Lapostolle F Surget V Borron SW et al.Severe pulmonary embolism associated with air travel.N Engl J Med. 2001; 345: 779-783Crossref PubMed Scopus (361) Google Scholar who showed that the risk of pulmonary embolism significantly increased with flights longer than 6 h, with the risk rising a further threefold after 12 h. Consistent with these findings, we observed that all participants with a VTE had a total duration of air travel of more than 24 h. As we explicitly stated, our findings are not necessarily applicable to most air travel which involves flights of shorter duration. We concur with Frédéric Lapostolle and colleagues' view that further research on risk factors associated with air traveller's thrombosis and the efficacy of preventive strategies is required. In terms of the potential role of risk factors, a case-control approach is the preferred epidemiological method, as undertaken by Martinelli and colleagues.3Martinelli I Taioli E Battaglioli T et al.Risk of venous thromboembolism after air travel: interaction with thrombophilia and oral contraceptives.Arch Intern Med. 2003; 163: 2771-2774Crossref PubMed Scopus (139) Google Scholar These researchers reported that, when thrombophilia or oral contraceptive use is present in air travellers, the risk of VTE increases around 15-fold. Analysis of the efficacy of preventive measures such as aspirin, low-molecular-weight heparin, or graduated compression stockings will require a large randomised clinical trial in high-risk individuals. Alternatively, it might be possible to nest an observational study of risk factors within a randomised trial of a preventive strategy to answer more than one question at once. Only with information from such studies will it be possible to make clear recommendations about appropriate risk assessment and prophylactic measures. Venous thromboembolism in long-distance air travellersSir—R J Hughes and colleagues (Dec 20/27, p 2039)1 report a proportional level of risk in travellers of all classes and recommend that the term economy class syndrome should be renamed traveller's thrombosis or air-travel-related venous thromboembolism. Full-Text PDF Venous thromboembolism in long-distance air travellersSir—The lack of a control group of short-haul flyers in R J Hughes and colleagues' article1 invalidates its conclusions. The authors have offered no evidence of whether the rate of clots among short-haul flyers (or any other comparison group) is the same, greater, or less than the rate among long-haul flyers. Therefore, they have offered no evidence that long-haul flying is the cause of the clots seen. It might be that short-haul flying (or a myriad of other behaviours, including sitting in one place for too long on land) poses an equal or greater risk. Full-Text PDF Venous thromboembolism in long-distance air travellersSir—One of the main points emphasised by R J Hughes and colleagues1 is the need for control groups in future studies on thromboembolic events associated with air travel. In studies without control groups, interpretation of the results can lead to unfounded conclusions. For example, among the nine patients with thrombo-embolic events after air travel that Hughes and colleagues studied, six were women, four wore compression stockings, and five took aspirin. In view of these results, one could erroneously conclude that wearing compression stockings and taking aspirin are risk factors for thromboembolic events. Full-Text PDF
Publication Year: 2004
Publication Date: 2004-03-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 2
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