Deep space travel may mean astronauts can’t get it up back on Earth
Adding to the growing research into the effects of long-haul spaceflights on the human body, researchers have found that the weightlessness and radiation exposure accompanying deep space travel can cause long-lasting erectile dysfunction. With crewed space missions planned for the near future, the findings highlight the importance of considering astronauts’ sexual health.
The allure of space and discovering (and possibly inhabiting) other planets has captivated humans for many years. To prove the point: there are currently 77 space agencies globally, 16 with launch capabilities, and a new record for the number of people in space at once – 20 – was achieved in May 2023.
But do we know enough about the effects deep space travel has on the body? Researchers have already examined some health risks associated with space travel, namely that it may negatively affect the brain, immune system, joints and cells. With the growing interest in crewed space missions, a new study has gotten personal, investigating the effects of long-duration spaceflight on a male’s ability to attain and maintain an erection.
Penile erection is a vascular event controlled by the autonomic nervous system. Parasympathetic pathways are ‘pro-erectile.’ Incoming signals activate connector nerve cells to stimulate nearby parasympathetic neurons, which transmit erection-inducing signals from the sacral spine to the penile blood vessels. Conversely, sympathetic pathways are ‘anti-erectile.’ Disruption of these neurovascular signaling pathways can result in erectile dysfunction (ED).
The vascular endothelium plays an important role in regulating penile vascular tone and promoting erection, mainly through the production of nitric oxide (NO), which relaxes the smooth muscle and increases blood flow to the corpus cavernosum of the penis.
The researchers simulated four weeks of spaceflight in 86 adult male rats, including weightlessness and exposure to varying levels of deep space galactic cosmic radiation (GCR), from zero to 1.5 gray (Gy), using the GCR simulator at the NASA Space Radiation Laboratory. The animals’ penile blood vessels and corpus cavernosum were studied following 12 to 13 months of recovery from the weightlessness and CGR exposures. The vessels and tissue were tested for their ability to constrict in response to drugs and electrical stimulation, and levels of NO metabolites were measured.
The results demonstrated that, even after a prolonged recovery period, nerve-mediated vascular reactivity was negatively altered by relatively low doses of CGR exposure. The radiation significantly impaired endothelial function and tissue relaxation and reduced NO metabolism byproducts, suggesting dysfunction of the NO pathway critical for normal erectile function. The researchers also noted increased levels of oxidative stress and reactive oxygen species (ROS) in the corpus cavernosum.
The vascular alterations were observed to a lesser extent following simulated weightlessness, primarily through increased oxidative stress. Acute treatment of corpus cavernosum tissue with antioxidants improved relaxation responses in the radiation-exposed rats.
“With [crewed] missions to outer space planned for the coming years, this work indicates that sexual health should be closely monitored in astronauts upon their return to Earth,” said Justin La Favor, corresponding author of the study. “While the negative impacts of galactic cosmic radiation were long-lasting, functional improvements induced by acutely targeting the redox and nitric oxide pathways in the tissues suggest that the erectile dysfunction may be treatable.”
The study was published in The FASEB Journal.