Long Trips Double Risk of Developing Blood Clots

Travelers who don't move around during long trips double their risk of developing a dangerous blood clot, the World Health Organization says. Deep-vein thrombosis is usually associated with air travel, but train, bus, and car passengers who sit for 4 hours or longer also risk the formation of clots, which usually afflict the lower legs and, more dangerously, the lungs.

The risk is greater for frequent fliers but overall relatively small: About one person out of 6,000 will suffer from the circulatory woes associated with long-haul travel. The statistics are part of a report released today that's been in the works since shortly after the 2001 death of an English woman who had recently returned home from Australia. (More travel stories.)