Ever since I was a kid, I’ve been interested in anything and everything related to space. The concept of humans traveling outside Earth’s orbit was mind-blowing and inspired me to pursue a career in aerospace engineering. After my first semester in college, I realized medicine was a more compelling career choice because I wanted to work directly with people and improve lives. But my passion for space has always been in the back of my mind.
In 2020, before entering pharmacy school, a colleague sent me a article in the New England Journal of Medicine about a group of doctors summoned by NASA to help prescribe a therapeutic regimen for an astronaut who developed left internal jugular vein thrombosis while on a mission aboard the International Space Station (ISS). A health incident like this had never been documented before, and the astronaut was prescribed a therapeutic regimen within days of the diagnosis: subcutaneous injections of enoxaparin daily for approximately 42 days, followed by apixaban orally twice daily for the remainder of the flight. The diet was split this way because there was initially a limited supply of anticoagulant available aboard the ISS, and no anticoagulation-reversal agent; apixaban should have been sent at a later date.
As an aspiring medical professional, I understood that astronauts needed medical care before, during, and after spaceflight, and would likely need specific countermeasures to protect them from stressors. potentially harmful in this extreme environment. With increased interest in commercial space tourism, coupled with NASA’s desire to extend trips to the Moon and Mars, the need for a better 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 field of study even existed.
Current research on health in space
While scientists have been collecting data for several decades, the implications of extended space travel are largely unknown.
In 2019, NASA published a study titled, “The NASA Twins Study: A Multidimensional Analysis of Year-Long Human Spaceflight.” This study is the only literature that documents the biological and physiological alterations that occur in humans during spaceflight longer than 6 months. In this study, two identical twin astronauts were subjected to more than 300 different samples to generate spatial data before the flight, in flight and after the flight. One of the twins was sent to the ISS for 12 months, while the other twin remained on Earth for that period; both astronauts were 50 years old at the time.
Scientists observed the following changes:
- Cardiovascular fluids move up the body and head during flight, with an increase in 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 increased release of cytokines and chemokines, as well as an inconsistent increase in biomarkers of oxidative stress in the vasculature; additionally, the adaptive, innate, and cell-mediated natural killer immune response was impaired
- Overall body mass was reduced by 7% and there was a reduction in urine volume
- Markers of bone resorption and formation increased by 50-60% during the first 6 months of flight, but then decreased over the last 6 months until immediately before landing.
- There were signs of retinal edema formation, signified by increased choroidal thickness and increased severity of the choroidal folds; this finding is consistent with previous studies, which have since coined the term neuro-ocular syndrome associated with space flight, or WITHOUT for short
- Microbiome alterations have occurred, but not at a significant or concerning level; alterations in DNA methylation and telomere length have also been observed
- Cognitive efficiency, measured by cognitive speed and accuracy using a computerized cognitive test, did not change during the flight, but decreased significantly 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 may be impacted by spaceflight were not considered in this study – from Intracranial pressure at Mental Health at traumaand countless others – but are currently being explored elsewhere. Several organizations and establishments from 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 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, I am particularly intrigued by the logistical and operational challenges encountered when approaching the safe use and storage of drugs in space. Medication dosage may need to be adjusted due to 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 drugs are altered in space, likely due to accelerated degradation due to exposure to cosmic radiation.
There are countless health-related avenues to consider when considering future space missions. While all of the aerospace medicine colleagues and mentors I have met at conferences and organizations so far have been brilliant, welcoming and encouraging, the need for more medical professionals and scientists studying this field is essential. Especially for medical students or early career professionals with a dual passion for healthcare and space, I implore you to consider exploring this field. Now is the time to get involved: aerospace medicine could very well be the next big revolution in healthcare.
Tom Diaz is a PharmD candidate at the University of North Carolina at Chapel Hill, graduating in 2024.
