Wearing compression stockings during airplane flights that last 7 hours or longer appears to reduce the risk of asymptomatic deep vein thrombosis, results of a Cochrane Library Review indicate.
In a review of 10 trials including a total of 2,637 passengers, 50 passengers developed symptomless deep vein thrombosis (DVT). Of them, 47 were not wearing compression stockings and 3 were wearing stockings, Mike Clarke, Ph.D., director of the UK Cochrane Center in Oxford, and his colleagues wrote.
“Wearing stockings might reduce the incidence of this outcome from a few tens per thousand passengers, to two or three per thousand,” they wrote. “Passengers who wear stockings will also experience less edema in their legs. However, this review is unable to identify whether these effects of wearing stockings translate into effects on outcomes such as death, pulmonary embolus, and symptomatic DVT.”
The researchers searched the Cochrane Centre Register of Controlled Trials, Medline, and other resources to locate randomized, controlled trials on the impact of compression stockings, compared with no stockings, on the incidence of DVT in passengers on flights lasting at least 4 hours.
Ten trials were identified: nine that involved 2,821 passengers and compared wearing stockings on both legs with not wearing them, and one trial that involved 35 passengers and compared wearing a stocking on one leg for the outbound flight with wearing one on the other leg for the return flight. All flights lasted at least 7 hours, and most stockings used in the trials were below the knee (Cochrane Database Syst. Rev. 2006;2:CD004002).
Of the nine trials involving 2,821 passengers, seven recruited a total of 1,548 passengers who were considered to be at low to medium risk of developing DVT, whereas the other two trials recruited 1,273 passengers who were considered to be at high risk.
Complete follow-up data were available for 2,637 passengers. Among these, 50 developed a symptomless DVT that was detected by either ultrasound or D-dimer testing and fibrinogen testing. Of these 50 passengers, 47 were not wearing compression stockings, and 3 were wearing stockings.
The overall incidence of symptomless DVT was 2.43% in the two trials of passengers considered to be at high risk vs. 1.45% in the seven trials of passengers considered to be at low or medium risk.
Six of the trials also showed that compression stockings significantly reduced leg edema in those who wore them.
“This review shows that the question of the effects on symptomless DVT of wearing versus not wearing compression stockings in the types of people studied in these trials should now be regarded as answered,” Dr. Clarke and his associates concluded.
“Further research may be justified to investigate the relative effects of different strengths of stockings or of stockings compared to other preventative strategies,” they added.