Space flight may increase erectile dysfunction among astronauts

Extended bouts in space could raise men’s risk of erectile dysfunction due to the effects of microgravity and cosmic radiation, according to experiments in rats.

The coming decades may see the return of crewed missions beyond Earth orbit. The US, for example, hopes to have astronauts walking on the moon again by 2025 and even aspires to set up a permanent base there. Meanwhile, talks of sending the first people to Mars have been ongoing for years.

But being in space may have some strange effects on our health. Previous research shows that microgravity reduces astronauts’ heart rates and blood pressure, with some even developing vision problems.

Now, Justin La Favor at Florida State University and his colleagues have found that space flight may lead to erectile dysfunction.

The team first simulated microgravity in rats via so-called hindlimb unloading. This involved lifting the back legs of 43 male rats and tilting them to a 30-degree angle, keeping them in this position for four weeks. A further 43 male rats were free to behave as normal in cages.

Within both groups of rats, different animals were exposed to varying amounts of a cosmic radiation simulation, made up of protons and ions: high levels, low levels or none at all.

Around a year later, the researchers looked for signs of erectile dysfunction in the rats. They determined this by measuring their oxidative stress, when antioxidant levels in the body are low, which has been linked to erectile dysfunction. Endothelial dysfunction, a narrowing of the blood vessels, has also been linked to the condition.

Exposing the rats to any amount of radiation led to much greater levels of oxidative stress and narrower blood vessels in the erectile tissue around their penises, compared with the animals with no radiation exposure.

The rats that only experienced microgravity also had these increased risk factors, but to a lesser extent than those that just had radiation exposure.

Microgravity and cosmic radiation exposure could impair astronauts’ erectile function long after they land back on Earth. However, hindlimb unloading is an imperfect simulation of what people experience in space, the authors write in their paper.

Treating the rats with antioxidants could help reverse some of these negative impacts, the authors write, but this hasn’t yet been tested.

“The major takeaway is that when these astronauts do return to Earth, they should be aware of and monitored for their sexual health,” says La Favor.