In space, even breathing can become a mission challenge. A new analysis of nearly two decades of medical logs from 71 International Space Station (ISS) crew members finds that sinus and nasal issues are among the most common health complaints in orbit – affecting 85 percent of astronauts.
Most dealt with at least one bout of congestion, and those who ventured outside the station on spacewalks reported even more trouble.
Spacewalks appeared to pile on, with those who performed them logging more complaints than their stay inside peers.
The study also shows that astronauts leaned on common over-the-counter remedies, but it is not clear that Earth-based solutions always translate well in orbit.
Astronauts’ health troubles in space
The work was led by Dr. Masayoshi Takashima, chair of the Department of Otolaryngology at Houston Methodist.
His team pulled de-identified events and medication records from NASA’s Lifetime Surveillance of Astronaut Health (LSAH) program to map symptoms across long missions.
Microgravity is to blame for breathing issues in space. In weightlessness, about two liters of fluid shift from the legs toward the head – a headward push that makes faces puffy and noses stuffy.
That shift is not just cosmetic. It raises pressure in head and neck vessels and can narrow the nasal airway, which explains why many astronauts feel congested early in flight.
What the ISS data shows
Across nearly 40 years of cumulative mission time, the logs captured 754 ear, nose, and throat events. General nasal congestion dominated the count, and 60 of the 71 astronauts reported at least one sinonasal event during their mission.
Medication records showed heavy use of decongestants. Pseudoephedrine was recorded 95 times, and oxymetazoline spray 51 times, with congestion listed as the top indication.
Astronauts whose records mentioned spacewalking logged, on average, 9.19 more sinonasal events than those without such mentions.
“Astronauts are typically among the fittest individuals on the planet, yet this study shows that even they experience substantial sinonasal complaints in space. Imagine what happens when civilians with preexisting conditions start traveling to space,” said Dr. Takashima.
Sinus pressure in suits
Extravehicular activity (EVA) means stepping into a spacesuit that operates at lower pressure than the station cabin. The current U.S. suit runs at about 4.3 psi on 100 percent oxygen, a setup that requires careful pre-breathing to manage decompression risk.
Russia’s Orlan suit runs higher, around 5.8 psi, and uses a different approach to operations and maintenance.
Pressure shifts place stress on the Eustachian tube, the small airway that equalizes pressure between the middle ear and the throat.
When it fails to open properly, barotrauma can follow. This can cause ear pain, muffled hearing, and a feeling of fullness – symptoms the study found often occurred around spacewalk days.
Space meds for astronauts
On airplanes back home, a single 120 mg dose of pseudoephedrine taken before flight reduces the rate of ear barotrauma compared with a placebo.
A head-to-head trial found that oxymetazoline nasal spray performed little better than a placebo for that same problem. This raises a fair question about its role as a go-to prophylaxis for spacewalks.
Space adds uncertainty because medication use is often self-treated and inconsistently recorded, and because drug behavior can change off-planet.
Reviews of space pharmacology note that absorption, distribution, and elimination may shift in microgravity. The data are still limited, which complicates dosing decisions for common drugs like decongestants.
“This is about maintaining peak performance,” said Dr. Takashima. “If you’re not sleeping well because you can’t breathe, your cognitive function, reaction time and mission performance can suffer, and those things are absolutely critical in space.”
Sinus relief in space
One countermeasure aims lower, not higher. Thigh cuffs called Braslet M sequester blood in the legs, reducing headward shifts and easing congestion early in flight.
Station life also means living with airborne particles that linger longer because there is little sedimentation. The ISS relies on HEPA-class filtration and regular vacuuming to keep particle counts down around vents.
Better documentation would help too. Studies show crew members are allowed to self treat common ailments and often do, which makes it hard to judge real-world effectiveness of decongestants or antihistamines in flight.
The future of astronaut health
As commercial flights and lunar work increase, pre-flight screening for nasal obstruction and treatable sinus disease becomes practical risk management.
NASA’s astronaut medical standards already call for ongoing selection and recertification to ensure medical conditions are compatible with mission tasks.
Future protocols could lean more on objective measures for congestion, standardized reporting for meds, and tailored prophylaxis before EVAs.
There is a need to evaluate different astronaut suit pressure settings, optimize pre-breathe protocols, and compare oral and topical interventions, focusing on meaningful outcomes such as sleep quality and reaction time in orbit.
The study is published in the journal Laryngoscope Investigative Otolaryngology.
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