Long-distance travel can lead to potentially fatal blood clots in some people and the risk grows in tandem with the length of the trip.
Several high-profile deaths have brought attention to the risk of venous thromboembolism (VTE) among travellers, particularly those on long-haul flights. VTE is a blood clot that forms within a vein. Thrombosis is a specific medical term for a blood clot that remains in the place where it was formed. Symptoms of a blood clot in the leg include pain, warmth, swelling and redness in the limb. If the clot travels to the lungs, it may cause sudden shortness of breath, chest pain or a cough that produces blood.
Researchers from America analysed 14 previous studies involving 4,055 American patients of venous thromboembolism (VTE) to estimate the risk for VTE in travellers and to determine whether a dose-response relationship existed. Factors like dehydration and hours of sitting in cramped conditions were considered to find out the reason for blood clots.
Some of the studies compared VTE patients with a control group of people who had been referred for possible VTE symptoms, but were found to not have a clot. In other studies, the control group consisted of healthy people from the general population (which are more likely to capture the true VTE risk associated with travel).
It was found that travel was associated with a nearly three-fold risk of VTE than non-travellers. The risk increased along with the duration of the trip - rising 18% for every two hours of any type of travel, and by 26% for every two hours of air travel. Certain people are at risk of blood clots including cancer patients, people who have recently had major surgery such as a joint replacement and women on birth control pills.
The researchers suggested that people who travel long distances should be aware of the risk of blood clots and recognise the symptoms. Symptoms of a blood clot in the leg include pain, warmth, swelling and redness in the limb. To reduce the risk of VTE, long-distance travellers should periodically move around and stretch their legs and drink plenty of water to stay hydrated.