Long-term space missions may make liftoff harder for male astronauts

Study suggests galactic cosmic radiation could damage below-the-belt tissues

Male astronauts who spend prolonged periods in space may suffer permanent erectile dysfunction, new research has found.

A NASA-funded study by researchers at Florida State University (FSU) and Wake Forest University of Medicine, published on Wednesday, suggests that long-term exposure to the hazards of space have serious effects on the tissues that make up male sex organs.

"During deep space missions, astronauts are exposed to high levels of galactic cosmic radiation (GCR) and microgravity which are associated with increased risk of oxidative stress and endothelial dysfunction," the team wrote in its paper. Both issues "are causative factors in the pathogenesis of erectile dysfunction, although the effects of spaceflight on erectile dysfunction have been unexplored."

Those of us stuck on the ground are largely protected from GCR, though we are still exposed to a bit of it that manages to make its way through the atmosphere. Astronauts, even those on the ISS, are shielded from GCR but still end up being exposed to far more than humans on Earth.

GCR is a unique form of radiation composed of high-energy protons, plus high charge and energy ions. It spreads through biological tissue differently than terrestrial radiation, the researchers note. This, they wrote, "triggers unique, more severe biological damage."

One such form of damage is to the vascular endothelium, which makes up the inner lining of veins, arteries and capillaries. Exposure to GCR leads to "decreases in NO [nitric oxide - a signaling molecule and key part of achieving erection] levels, greater incidences of apoptosis [cell death], and morphological changes including cell shrinkage, wider gaps between cell junctions and detachment from the basement membrane."

All that "negatively affect[s] endothelium-dependent vasodilation." I.e., it becomes harder to achieve an erection.

To investigate the extent of the damage, the boffins exposed 86 adult male rats to four weeks of simulated microgravity and GCR. The rats were given around a year to recover from their experience, then examined.

"Findings indicate that simulated spaceflight exerts a long-term impairment of neurovascular erectile function, which exposes a new health risk to consider with deep space exploration," the researchers said in their paper.

The researchers opined their work is the first of its sort and suggest sexual function in male astronauts could be impaired "for the remainder of [their] sexual health space following return to Earth from prolonged deep space exploration."

"With manned 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," suggested FSU's Dr. Justin La Favor, one of the study’s authors.

There is a potential solution, however, in the form of antioxidant treatments for erectile tissue. "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," La Favor noted.

Determining the potential damage to human reproduction is critical as long-term space exploration is planned, the team said. Future work, they noted, should also investigate the impacts of space flight on female sexual function as well, which wasn't part of this study. ®

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