Travel Raises Risk of Blood Clots Threefold

We all know how exciting it is to go on a well-needed vacation, but it has been shown that traveling long distances by bus, train, car, or plane could nearly triple a person’s risk of developing blood clots in the leg veins and lungs. According to recent research published online in the Annals of Internal Medicine, for each two-hour increase in travel time, the risk of getting a clot, also known as venous thromboembolism, increased approximately 18 percent. For the people who travel by plane, the risk rose approximately 26 percent for every two-hour increase in time spent in the air.

According to lead author, Divay Chandra, the review looked at 14 previous studies, which included 4,055 cases, and is the largest and most comprehensive review to find that travel increases the risk of developing blood clots. There are more than 200,000 new cases of venous thrombeombolism occurring each year in the U.S. with a 30 percent risk of death within 30 days, according to the American Heart Association.

Chandra, who is also a fellow in the division of pulmonary, allergy and critical care medicine at the University of Pittsburgh Medical Center, stated, “People who travel, particularly if they travel long distances, they should be aware of these symptoms. They should not be ignored.”

According to the U.S. Department of Health and Human Services, symptoms of a blood clot include, but are not limited to, redness of the skin, pain or soreness in the legs and arms, swelling in the legs or arms or warm spots on the legs. To avoid clots, travelers should drink plenty of water and stop to walk occasionally while on route to help prevent the development of clots.

Studies that were previously conducted have reported conflicting results on whether long-distance travel was actually linked to blood clots. To resolve this question, Chandra and her colleagues at Harvard Medical School compared 14 studies that looked at the rate of blood clots in people that travel to the people who did not travel. Combining the results, the researchers found double the number of blood clots in the group that traveled. According to Chandra, 6 out of the 14 studies did not use the best study design because the comparison group of the people who did not travel had been previously selected for testing to see if they already had clots. Excluding the results from those six studies, they found that the risk of developing a blood clot approximately tripled for the travelers. The researchers also saw that the risk was also higher for those who traveled by plane when compared with those who took ground transportation, however, the increase was not statistically significant.

The analysis drew its conclusions by going over the results of the studies conducted and reported the relative risks, rather than on the number of cases. To help illustrate exactly how high the odds could be for any one traveler, the article cited a previous study estimating that one blood-clot case occurred for every 4,600 airplane flights.

According to the NIH, the blood clots that form in the legs could be fatal if they were to break loose and move to other parts of the body, which includes the lungs. According to the American Heart Association, approximately 20 percent of those that suffer from a clot in the lungs, or pulmonary embolism, suffer sudden death.

Physicians are still researching exactly why traveling could cause blood clots, and some suspect that the lack of mobility may discourage the flow of blood and enable clots to form. Future studies will be need to show if travelers could lower their risks by drinking fluids, stopping to walk along the way or taking other measures before they start on their trip, Chandra said.

People that are considered to be at a high risk for blood clots, which include smokers, cancer patients and those who have suffered from clots before, should speak with their physician and may need to take blood thinners before trying to make a long trip.