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OC Users at Increased Risk for VTE When Flying?
The media have reported that women on the pill are at higher risk, but the data are not convincing.
Prolonged air travel has been associated with venous thromboembolism (VTE; i.e., pulmonary embolism or deep-vein thrombosis). These researchers examined other risk factors for VTE, including oral contraceptive (OC) use and thrombophilia, among air travelers.
A total of 210 consecutive patients (103 women) presenting with first episodes of VTE at a thrombosis center in Italy were matched with 210 controls of the same age, sex, and education level. Nearly half of the patients had no transient risk factors for VTE (e.g., surgery, immobilization). Thirty-one VTE patients and 16 controls reported air travel in the preceding month, with flights 
8 hours reported by 11 patients and 4 controls.
VTE was 3 times more likely to occur in those who had flown long distances than in those who had not. Further, VTE was 16 times more likely to occur in flyers with thrombophilia than in nonflyers without thrombophilia. Eight VTE patients and 1 control had both flown in the past month and used OCs. VTE risk was 14 times higher among OC users who had flown than among nonusers who had not flown; risk was 23 times higher after adjustment for age and BMI. However, the confidence intervals for these odds ratios were very wide (1.7-117.5 and 2.6-211.2, respectively).
Comment: The media interpreted these data as showing that OC users are at higher risk for VTE when flying. However, only 8 cases and 1 control had flown during OC use, and the confidence intervals for the odds ratios were extremely wide. The reported association between OC use and increased VTE risk when flying is not convincing. Nevertheless, although we don't know whether conventional recommendations, such as remaining hydrated with nonalcoholic fluids and performing leg exercises, are sufficient to decrease VTE risk during air travel, such measures aren't harmful and appear to be prudent for all flyers.
— Diane E. Judge, APN/CNP
Published in Journal Watch Women's Health February 11, 2004
Citation(s):
Martinelli I et al. Risk of venous thromboembolism after air travel: Interaction with thrombophilia and oral contraceptives. Arch Intern Med 2003 Dec 8/22; 163:2771-4.
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