The association between air travel and deep vein thrombosis: systematic review & meta-analysis.

BACKGROUND: Air travel has been linked with the development of deep vein thrombosis (DVT) since the 1950s with a number of plausible explanations put forward for causation. No systematic review of the literature exploring this association has previously been published. METHODS: A comprehensive search was undertaken (Data bases searched were: MEDLINE, EMBASE, Cochrane Library) for studies that estimated both the incidence and the risk of DVT in air travellers relative to non-air travellers. RESULTS: In total 254 studies were identified but only six incidence studies and four risk studies met inclusion criteria justifying their use in a systematic review. Incidence of symptomatic DVT ranged from (0%) in one study to (0.28%) which was reported in pilots over ten years. The incidence of asymptomatic DVT ranged from (0%) to (10.34%). Pooled odds ratios for the two case control studies examining the risk of DVT following air travel were 1.11 (95% CI: 0.64-1.94). Pooled odds ratios for all models of travel including two studies of prolonged air travel (more than three hours) were 1.70 (95% CI: 0.89-3.22). CONCLUSION: We found no definitive evidence that prolonged (more than 3-hours) travel including air travel, increases the risk of DVT. There is evidence to suggest that flights of eight hours or more increase the risk of DVT if additional risk factors exist.