Microgravity Alters Blood Clotting in Women, Study Reveals
A recent study by Simon Fraser University (SFU) and the European Space Agency (ESA) indicates that even a few days in simulated microgravity can subtly alter blood clotting mechanisms in women. The research, which involved 18 female participants, found that while blood took longer to begin clotting, the resulting clots formed more rapidly and were stronger and more stable. These findings prompt further investigation into potential health risks for female astronauts during extended space missions.
While blood took longer to begin clotting, the resulting clots formed more rapidly and were stronger and more stable.
Background to the Research
The study was initiated following an incident in 2020 where a female astronaut on the International Space Station (ISS) developed an unexpected blood clot in her jugular vein. Historically, space-health research has predominantly focused on male participants.
As the number of women participating in space missions increases, there is a growing need to understand gender-specific physiological responses to spaceflight. This research aims to address potential health monitoring requirements for female astronauts.
Study Design and Key Findings
The SFU and ESA-sponsored VIVALDI I dry immersion study involved 18 female participants who underwent five days of continuous simulated microgravity using a dry immersion tank. Rotational thromboelastometry (ROTEM), a diagnostic method, was used to measure blood clotting responses.
Key observations from the study included:
- Coagulation time, the period before blood clots began to form, was longer.
- Once initiated, clots formed more rapidly.
- After formation, the strength and stability of the clots were greater, making them potentially more difficult to break down.
Analysis of participants' blood also indicated that menstrual hormones had no discernible effect on blood coagulation within the study's context. The research also supports existing evidence of a greater risk of venous thromboembolism in women and identified hypercoagulability as a potential underlying mechanism.
Implications for Spaceflight
While the observed changes were not considered clinically concerning after only five days in simulated microgravity, researchers state they necessitate further investigation for longer space missions. Andrew Blaber, a professor of biomedical physiology and kinesiology and senior author, noted that the combination of slower initiation, faster formation, and stronger clots was not inherently dangerous in the short term.
However, lead author Tiffany Stead indicated that these changes raise concerns regarding the formation of blood clots in space, particularly due to the limited availability of emergency medical care during missions.
On Earth, gravity typically causes blood clots to form in the legs. In microgravity, the absence of gravitational force leads to blood pooling in the head, and sometimes a reversal of blood flow, which increases the likelihood of clot formation.
Professor Blaber explained that in space, blood clots are more prone to forming in the jugular vein. Clots from this location have a shorter distance to travel to vital organs such as the lungs or heart, potentially causing serious medical events, including pulmonary embolism, heart attack, or stroke. These considerations are relevant for crews on long-duration missions, such as those planned for NASA's Artemis Program to the Moon and future expeditions to Mars.
Response and Ongoing Research
In response to the 2020 incident, space agencies have implemented regular jugular vein ultrasound scans for astronauts on the ISS. Professor Blaber's team is currently analyzing comparable data from male dry immersion studies to further understand gender-specific responses and inform future medical monitoring and countermeasures for spaceflight.
The study findings were published in the journal Acta Astronautica.