Results of recent studies suggest that the risk of developing deep vein thrombosis (DVT) or 'Economy Class Syndrome' during a long-haul flight is extremely small. However they also show that frequent travelers, seniors, those who are overweight or obese, and women taking birth control pills are at significantly higher risk of developing the condition. Results of a five-year long study by Dr Esteban Perez-Rodriguez of Ramon y Cajal Hospital in Madrid, Spain, revealed that 0.39 cases of lung blood clot - the most serious kind of travel-related DVT - occurred for every 1 million passengers on flights of six to eight hours. On flights of eight hours or more the risk rose to 1.65 per million passengers. Meanwhile results of another study by Dr Ida Martinelli and colleagues at the University of Milan, Italy, revealed that certain populations were at significantly increased risk of developing Economy Class Syndrome. Clots were twice as common in people who had recently been on another flight, and 14 times as common in women who were taking birth control pills but were not frequent travelers.  A third study by German researchers showed that being old, overweight, or having varicose veins also increased the risk of developing blood clots. Dr Thomas Schwarz and colleagues at the University of Dresden Medical School in Germany found that the average age of passengers who developed clots was 66.

SOURCE/REFERENCE: Arch Intern Med. 2003;163:2759-2764, 2766-2770, 2771-2774.