Lengthy travel may not increase blood clot risk

NEW YORK (Reuters Health) - You've seen all of the warnings about blood clots forming on long plane trips if you sit still, but a new study suggests that such inactivity may not actually increase the risk of clots.

On the other hand, the findings suggest that keeping your whole body, or a single limb, immobile due to paralysis or injuries could put you at risk of blood clots that may spread to the lungs and cause serious harm or death.

Dr. Jeffrey Kline, from the Carolinas Medical Center in Charlotte, North Carolina, and co-authors studied 7940 emergency department patients who were evaluated for blood clots between 2003 and 2006.

They report in the Annals of Emergency Medicine that 545 patients were diagnosed with venous blood clots within 45 days, and 1394 had at least one reason for immobility. Those included being bed-bound, travel of more than 8 continuous hours in the previous week, and paralysis due to brain injury or disease.

Compared with patients with no immobility, immobility of a limb was most strongly linked with a blood clot, closely followed by paralysis due to brain injury or disease.

Although travel was the most frequently observed reason for immobility, there was no evidence that it was linked to blood clots.

Dr. Kline's team believes that "many experts would assert a risk exists between (blood clots) and air travel," but they note that no study has specifically examined this issue.

SOURCE: Annals of Emergency Medicine, August 2009.