When a 28-year-old British woman collapsed at London's Heathrow airport in September after a trip to Australia and later died, allegedly from a deep vein thrombosis (DVT) causing an embolism, the controversy over whether long flights increase the risk of DVT (known as "economy-class syndrome") again attracted the spotlight.

A 1998 study in Aviation Space and Environmental Medicine reported that of 134 patients hospitalized with DVT, 33 had traveled by plane within the previous 31 days; among these, eight (24%) developed symptoms during air travel or on the day of arrival, and 27 (82%) did so within 15 days.

But not everyone agrees that long flights are the cause of DVT among travelers. Dutch researchers who published a study in the October 28 issue of Lancet are among the dissenters. Of 788 patients (mean age, 62), a quarter were confirmed to have DVT. The travel habits of this group were compared to those of a control group consisting of the remaining 602 patients. The researchers found no association between travel (by plane, car, bus, train, or boat) and increased DVT risk.

Although there is still doubt about a link between DVT and long flights, travelers can follow guidelines to ensure a safe flight. The Mayo Clinic Heart Book (William Morrow & Co, 2000) recommends wearing comfortable clothing and shoes; frequently stretching legs, even while sitting; not crossing legs; walking at least once per hour; avoiding alcohol; staying hydrated; and taking aspirin, if appropriate.