Since I was a child, I have had an interest in everything related to space. The concept of humans traveling outside of Earth’s orbit was mind blowing and 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 life. But my passion for space has always been on my mind.
In 2020, before I entered the pharmacy school, a colleague sent me an article in the New England Journal of Medicine about a group of doctors summoned by NASA to assist in prescribing a treatment regimen for an astronaut who developed thrombosis in the 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 treatment regimen was prescribed for the astronaut within days of diagnosis: subcutaneous injections of enoxaparin every day for approximately 42 days, followed by oral apixaban twice daily for the rest of the flight. The regimen was split this way because initially there was a limited supply of anticoagulant available aboard the ISS and no anticoagulant-reversing agent; apixaban was to be sent at a later time.
As an aspiring healthcare professional, I have realized that astronauts require medical attention before, during and after space flights and will likely require specific countermeasures to protect them from potentially damaging stressors in this extreme environment. With the growing interest in commercial space flight tourism, coupled with NASA’s desire for extended travel 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 started wondering if there was a career opportunity for me in this field and to what extent this area of study existed.
Current research on health in space
Although scientists have been collecting data for several decades, the implications of long space travel are largely unknown.
In 2019, NASA published a study titled “The NASA Twins Study: A Multi-Dimensional 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 during space flight for more than 6 months. In this study, two identical twin astronauts were subjected to over 300 different samples in order to generate space data before flight, during flight and after flight. One of the twins was sent to the ISS for 12 months, while the other twin remained on Earth during this time period; both astronauts were 50 years old at the time.
Scientists observed the following changes:
- Cardiovascular fluids move to the upper body and head during flight, with increased cardiac output, systolic output, and thickness of the carotid intima media, but a decrease in mean arterial pressure and blood volume
- There was evidence of an increase in inflammation, indicated by an increase in the release of cytokines and chemokines, as well as an inconsistent increase in biomarkers of oxidative stress in the vascular system; furthermore, the adaptive, innate and natural killer cell-mediated immune response was altered
- Overall body mass was reduced by 7% and a reduction in urine volume occurred
- Markers of bone resorption and formation increased by 50-60% during the first 6 months of flight, but then decreased in the last 6 months until just before landing
- There was evidence of retinal edema formation, indicated by increased choroid thickness and increased severity of the choroidal folds; this finding is consistent with previous studies, which have since coined the term spaceflight-associated neuro-ocular syndrome, or SANS for short.
- Alterations to the microbiome have occurred, but not to a level of significance or concern; Alterations in DNA methylation and telomere length were also observed
- Cognitive efficiency, as measured by cognitive speed and accuracy through a computerized cognitive test, remained unchanged during the flight, but was significantly reduced after the flight
Although the exact etiology of these physical and biological changes has not been confirmed, several hypotheses exist. For example, the combined effect of weightlessness, cosmic radiation, and isolation is thought to cause some of these changes. A plethora of other physiological changes or health-related situations that can be affected by space flight have not been 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 hopes of adequately preparing our species for extended travel 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 of which I am particularly intrigued is the logistical and operational challenges faced when approaching the safe use of drugs and storage in space. Medication dosage may need to be adjusted due to the pharmacokinetic and pharmacodynamic changes occurring in humans due to the myriad of physiological alterations we have seen so far in studies. Additionally, the stability and shelf life of drugs are altered while in space, possibly due to accelerated degradation from exposure to cosmic radiation.
There are countless health-related avenues to consider when thinking about future space missions. While every aerospace medicine colleague and mentor I have met at conferences and organizations thus far has been brilliant, welcoming and encouraging, the need for more healthcare professionals and scientists to investigate 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.