Since I was a child, I had an interest in everything related to space. The concept of humans traveling beyond Earth’s orbit was mind-blowing and inspired me to pursue a career in aerospace engineering. After my first semester of 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, before I entered the Faculty of Pharmacy, a colleague sent me an article in New England Journal of Medicine about a group of doctors called in by NASA to help prescribe a therapeutic regimen for an astronaut who developed thrombosis in his 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 to the astronaut within days of the diagnosis: subcutaneous injections of enoxaparin daily for about 42 days, followed by oral apixaban twice daily for the remainder of fields. The regimen was divided in this way because initially there was a limited supply of anticoagulant on board the ISS and no anticoagulant; apixaban was to be sent at a later date.
As an aspiring health professional, it occurred to me that astronauts need medical attention before, during, and after spaceflight and will likely need 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 to better understand human health and biology following prolonged exposure to the space environment is imperative.
I began to wonder if there was a career opportunity for me in this field — and to what extent this field of study even existed.
Current health research in space
While scientists have been collecting data for several decades, the effects of extended space travel are largely unknown.
In 2019, NASA published a study titled “The NASA Twins Study: A Multidimensional Analysis of a One-Year Human Spaceflight.” This study is the only body of literature that documents the biological and physiological changes that occur in humans during spaceflight longer than 6 months. In this study, two identical twin astronauts were subjected to over 300 different samples to generate pre-flight, in-flight and post-flight space data. One of the twins was sent to the ISS for 12 months, while the other twin remained on Earth during that time period; both astronauts were 50 years old at the time.
Scientists observe the following changes:
- Cardiovascular fluids shift to the upper body and head during flight, with increased cardiac output, stroke volume, and carotid intima-media thickness, but decreases in mean arterial pressure and blood volume
- There is evidence of increased inflammation as indicated by increased release of cytokines and chemokines, as well as inconsistent increases in biomarkers of oxidative stress in the vasculature; in addition, the adaptive, innate, and killer cell-mediated immune response is altered
- Total body mass was reduced by 7% and there was a decrease in urine volume
- Markers of bone resorption and formation increased 50-60% during the first 6 months of flight but then decreased during the last 6 months until just before landing
- There are data on the formation of retinal edema, expressed by increased choroidal thickness and increased severity of choroidal folds; this finding is consistent with previous studies that have since coined the term spaceflight-associated neuro-ocular syndrome, or SANS for short
- Changes in the microbiome have occurred, but not to a degree of significance or concern; changes in DNA methylation and telomere length were also observed
- Cognitive performance, as measured by cognitive speed and accuracy using a computerized cognitive test, was unchanged during flight but was significantly reduced after flight
Although the exact etiology of these physical and biological changes has not been confirmed, several hypotheses exist. For example, the combined effects 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 may be affected by spaceflight were not considered in this study—from intracranial pressure to mental health to trauma and countless others—but are currently being investigated elsewhere. Several organizations and institutions around the world are collaborating to learn more about the short- and long-term health effects of spaceflight in hopes of properly preparing our species for extended journeys beyond low-Earth orbit.
Uncharted Territory: Many questions remain
Researchers have barely scratched the surface of health and healthcare in space, especially after extensive space exploration. As a pharmacology student, one area I am particularly intrigued by is the logistical and operational challenges I face when approaching the safe use and storage of drugs in space. Drug dosing may need to be adjusted as a result of the pharmacokinetic and pharmacodynamic changes that occur in humans due to the myriad physiological changes we have witnessed in studies to date. In addition, the stability and shelf life of drugs change while in space, possibly due to accelerated degradation from exposure to space radiation.
There are countless health-related options to consider when thinking about future space missions. Although every aerospace medicine colleague and mentor I have met at conferences and organizations so far has been bright, welcoming and encouraging, the need for more healthcare professionals and scientists researching this field 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 on board is now: space medicine could 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.