Since I was a child, I’ve had an interest in anything and everything space-related. The concept of humans traveling outside of Earth’s orbit was mind-blowing, and it inspired me to pursue a career in aerospace engineering. After my first semester in college, I realized that medicine was a more compelling career choice, because I wanted to work directly with people and improve lives. But my passion for space was always in the back of my mind.
In 2020, prior to entering pharmacy school, a colleague sent me an article in the New England Journal of Medicine about a group of physicians summoned by NASA to assist in prescribing a therapeutic regimen for an astronaut who had developed a thrombosis in her left internal jugular vein during a mission aboard the International Space Station (ISS). A health incident like this had never been documented before, and a therapeutic regimen was prescribed for the astronaut within days of the diagnosis: subcutaneous enoxaparin injections every day for about 42 days, followed by oral apixaban twice a day for the remainder of the flight. The regimen was split up this way because there was initially a limited supply of anticoagulant available aboard the ISS, and no anticoagulation-reversal agent; apixaban had to be sent up at a later date.
As an aspiring healthcare professional, it dawned on me that astronauts require medical attention before, during, and after space flights, and will likely require specific countermeasures to protect them from potentially harmful stressors in this extreme environment. With increased interest in commercial spaceflight tourism, coupled with NASA’s desire for extended trips to the moon and Mars, the need for a greater understanding of human health and biology after prolonged exposure to a space environment is imperative.
I began to wonder if there was a career opportunity for me in this field — and to what extent this area of study even existed.
Current Research on Health in Space
While scientists have been gathering data for several decades, the implications of extended trips to space are largely unknown.
In 2019, NASA published a study titled, “The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight.” This study is the only piece of literature that documents the biological and physiological alterations that occur in humans in spaceflight longer than 6 months. In this study, two identical twin astronauts were the subjects of over 300 different samples in order to generate preflight, inflight, and post-flight space data. One of the twins was sent to the ISS for 12 months, while the other twin stayed on Earth during this time period; both astronauts were 50 years old at the time.
Scientists observed the following changes:
- Cardiovascular fluids shift to the upper body and head during flight, with an increased cardiac output, stroke volume, and carotid intima-media thickness, but a decrease in mean arterial pressure and blood volume
- There was evidence of increased inflammation, indicated by an increase in cytokine and chemokine release, as well as an inconsistent increase of biomarkers of oxidative stress in the vasculature; in addition, the adaptive, innate, and natural killer cell-mediated immune response were altered
- Overall body mass was reduced by 7%, and there was a reduction in urine volume
- Markers of bone resorption and formation were increased by 50-60% during the first 6 months of flight, but then decreased during the last 6 months until immediately before landing
- There was evidence of retinal edema formation, signified by increased choroidal thickness and increased severity of choroidal folds; this finding is consistent with previous studies, which have since coined the term space-flight associated neuro-ocular syndrome, or SANS for short
- Microbiome alterations occurred, but not to a level of significance or concern; alterations in DNA methylation and telomere length were also observed
- Cognitive efficiency, measured by cognitive speed and accuracy through a computerized cognitive test, were unchanged during flight, but were significantly decreased post-flight
While the exact etiology of these physical and biological changes haven’t been confirmed, several hypotheses exist. For example, the combined effect of weightlessness, cosmic radiation, and isolation are thought to cause some of these changes. A plethora of other physiological changes or health-related situations that can be impacted by space flight were not considered in this study — from intracranial pressure to mental health to trauma, and countless others — but are currently being explored elsewhere. Several organizations and institutions around the world are collaborating to learn more about the short- and long-term health impacts of space flight in the hopes of properly preparing our species for extended trips outside of lower earth orbit.
Uncharted Territory: Many Questions Remain
Researchers have barely scratched the surface of health and healthcare in space, especially after prolonged space exploration. As a pharmacology student, one area I am especially intrigued by is the logistical and operational challenges faced when approaching safe medication use and storage in space. Medication dosing may need to be adjusted as a result of the pharmacokinetic and pharmacodynamic changes that occur in humans due to the myriad of physiological alterations we have witnessed in studies thus far. In addition, the stability and shelf-life of medications are altered while in space, likely due to accelerated degradation from cosmic radiation exposure.
There are countless health-related avenues to consider when thinking about future missions to space. While every aerospace medicine colleague and mentor I have met through conferences and organizations so far have been bright, welcoming, and encouraging, the need for more healthcare professionals and scientists investigating this area is essential. Especially for any medical students or early-career professionals with a dual passion for healthcare and space, I implore you to consider exploring this field. The time to get involved is now: aerospace medicine could very well be the next big thing in healthcare.
Tom Diaz is a PharmD candidate at the University of North Carolina at Chapel Hill, graduating in 2024.