Study shows how to reduce the risk of thrombosis in female astronauts

Hyperaxion May 18, 2020

After a case occurred at the International Space Station, scientists assess how professionals who take contraceptives on space missions can prevent the condition.

A study of female astronauts, published in early May in the journal Aerospace Medicine and Human Performance, proposes guidelines for female astronauts for the prevention of deep vein thrombosis (DVT) in space missions.

Study shows how to the reduce risk of thrombosis in female astronauts
(Credit: Creative commons).

The issue came to light after the unusual case of an unidentified astronaut being diagnosed and treated with a blood clot during a flight on the International Space Station in 2019. The concern that such an occurrence will happen again fell mainly on women astronauts, who use combined contraceptive pills (which contains estrogen and progesterone) to avoid having periods while on space. These drugs are risk factors for the development of DVT.

Fortunately, when analyzing data on the health condition of 38 female astronauts who participated in space missions between 2000 and 2014, the researchers found no association between the use of combined contraceptives, space flights and the development of thrombosis.

Still, the authors of the study led by Varsha Jain, a visiting researcher at King’s College London, UK, made some suggestions to reduce the risks.

According to the sample of astronauts who participated in the study, the average age of a woman who goes into space is 44.6 years – an age at which, on Earth, the use of combined contraceptives would not be recommended, because of the risks of developing a clot.

Even so, these drugs are indicated for astronauts to interrupt the menstrual cycle, since hygiene conditions in space are quite limited. “When taken continually the pill can stop women from having periods in space, which is difficult given that washing water is limited and changing sanitary products while floating in space is challenging,” explains Varsha Jain, in an article published in The Conversation.

NASA astronaut Cady Coleman, Expedition 26 flight engineer.
NASA astronaut Cady Coleman, Expedition 26 flight engineer. (Credit: NASA).

Because of the need to use the pill, the researchers recommended some precautionary measures. Instead of taking combined pills, astronauts could take progesterone pills, which considerably lowers the risk of DVT.

Still, estrogen plays an important role in regulating the body of astronauts, as it is associated with properties that protect bones. Bone and muscle loss are a problem faced by these professionals. Therefore, the researchers recommend that, if necessary, astronauts use smaller and safer doses of estrogen, in addition to the pill.


The researchers also have guidelines for astronauts in general, men or women. According to them, the ideal would be more rigorous blood tests on the candidates during the selection phase for space missions, to assess what are the real risks of developing DVT.

Some pre-mission training exercises for space flights should also be reviewed. “Activities during pre-mission training – for example long-haul travel or diving exercises to simulate the space environment – may transiently increase the risk of a blood clot developing,” says Jain. “We therefore recommend that the timings of these events should be reviewed so that they do not occur in close succession, therefore inadvertently increasing the overall risk of developing a blood clot.”

Astronaut Peggy Whitson at the International Space Station in 2016.
Astronaut Peggy Whitson at the International Space Station in 2016. (Credit: NASA).

In a press release, Virginia Wotring, an associate professor at the International Space University and co-author of the research, stresses the importance of further studies with female astronauts, as most of them investigate only the effects of space travel on men. “[That’s because] most of the astronauts were male. That has changed, and now we need to understand how the spaceflight environment impacts female physiology,” she argues.

The study was carried out in partnership with members of the Baylor College of Medicine and the Lyndon B. Johnson Space Center, in the United States, and the International Space University, based in France.


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