NASA funds blood clot risk studies

blood draw
Giving blood to measure clot formation and breakdown factors (Beth Taylor photo)

Life’s circumstances can inspire research project ideas. For example, after running the Boston Marathon, a female athlete flew back home to Seattle and developed a blood clot or venous thrombosis. The runner’s sister, who is an exercise scientist in kinesiology, started searching for answers.

Initial literature reviews in 2010 showed that Associate Professor Beth Taylor, the exercise scientist, might be on to something. Studies seemed to suggest that a combination of risk factors, which includes flying long distances after endurance exercise and using estrogen-based oral contraceptives, had the potential to make women more susceptible to blood clots. As a result, several UConn research projects ensued with Taylor as one of the investigators.

Blood clot risk factors in women

NASA Connecticut Space Grant Consortium supplied some of the funding. Kinesiology 4th year doctoral candidate Amanda Zaleski received a $20,000 fellowship from them to test the hypothesis that active women in flight are at risk for blood clots.

NASA is especially interested in what flying, with its cabin pressure, confined spaces, compression of veins and reduced movement, does to the body. In addition, the agency has a goal to examine any evidence of barriers or workplace challenges negatively impacting women, who are at or want to work for NASA.

Amanda Zaleski
Amanda Zaleski

Zaleski said, “Estrogen-based oral contraceptives increase the risk of a venous thrombosis fivefold, while travel more than four hours coupled with endurance activity increases the risk two-and-a-half times.” While this is not detrimental to a majority of individuals, certain factors, such as oral contraceptives, can tip this balance.

Taylor calls this the “perfect storm hypothesis.” She said, “While it isn’t a public health epidemic, it’s concerning because the implications of a blood clot are substantial. If the blood clot travels to the lungs (a pulmonary embolism), mortality risk is 20%. And, an athlete who has a blood clot is at about a 30% greater risk of having another one.”

Research into the issue helps exercise physiologists in their goal of augmenting the benefits and diminishing the risks of exercise for the individual, according to Taylor.

This particular research study looked at flying plus other risk factors, such as being active, which is defined as getting 150 minutes or more of moderate exercise per week, and the use of oral contraceptives. Therefore, the problem of blood clots could affect marathoners and other athletes, members of the military, flight crews, aviation personnel and future commercial space travelers.

Compression socks as an intervention

Because blood clots can lead to serious problems, Zaleski also pursued funding for corollary research into preventative techniques. In 2015, she received an American College of Sports Medicine NASA Space Physiology Grant for a study called “The Effect of Compression Socks on Blood Clot Risk During Travel in Oral Contraceptive Using Women.”

compression socks
Compression socks awaiting owners. Some runners wore them to study the effect of compression socks on blood clot risk; others did not. (Beth Taylor photo)

“Compression socks were chosen as the most logical intervention because they are accessible, low-risk and low-cost,” Zaleski said. Other methods that might combat blood clots in the legs and maintain the hemostatic balance during flight include walking in the plane, maintaining hydration and stretching one’s legs, but these measures might be more difficult for researchers to quantify.

Methods for both studies

In both studies, the investigators enlisted subjects who flew to participate in marathons. Doing the studies in nearby Hartford and Boston gave the research team relative easy access to a large sample that met their parameters. This is an important group to concentrate on because marathon running has increased in popularity during the last two decades and a growing number of athletes travel long distances to and from competitive events, according to Zaleski.

Methods included performing blood tests before the flight to the Northeast, on landing, after the marathon and after flying home. The marathon field studies are what Zaleski calls “intense data collection,” and they require a great deal of collaboration and field orchestration. Another challenge is variable conditions with the possibility of pouring rain or freezing temperatures and dehydrated subjects.

In the compression sock study, researchers were trying to measure travel-induced blood clot risk and looked at two groups of subjects plus a control. They were 1) women not using oral contraceptives (the control group), 2) women using oral contraceptives and 3) women taking oral contraceptives and wearing compression socks on both flights to and from the marathon. However, the subjects did not wear the supplied socks during the marathon or on any training runs the week before the marathon.

What was found?

Some of life’s circumstances turn out better than expected. For example, news from Taylor’s sister shows that she made a full recovery from the blood clot and continues to participate in endurance events.

At other times, it is harder to determine the final outcome of events. In the first study of active women who fly, the findings seem like good news, but Zaleski cautions that the results need to be confirmed by a much larger study.

She explains, “Contrary to our hypothesis, women on oral contraceptives did not appear to have an increased risk of blood clot when traveling to and competing in endurance events. This was surprising given that both oral contraceptives and travel alone are often cited as and shown to be independent risks for blood clots.”

Occasionally in research, as in life, expectations are not met the way people think they should be. This can motivate researchers to explore other possible solutions.

For instance, the compression socks worn during a flight seemed to disrupt the hemostatic balance, which could promote blood clots. This led the researchers to wonder if compression sock use during the marathon instead of while travelling to and from the marathon might be more beneficial to the athletes. The timing of compression sock use for mitigating potential thrombotic risk associated with air travel to and from athletic events is a topic that needs more study.

Besides Taylor and Zaleski, Department of Kinesiology Distinguished Professor Linda Pescatello (major advisor) and doctoral students in kinesiology Lauren Corso, Gregory Panza and Yin Wu were involved in one or more of these studies.

By Patsy Evans