In 2005, NASA astronaut John Phillips reported a worrying symptom: On board the International Space Station (ISS), his vision had changed. Orbiting 254 miles above Earth, the world had become blurry.
Phillips was the canary in the coal mine. NASA tested other astronauts' vision, finding that the majority suffered similar changes. In fact, they appeared to have changes in the structure of their eyes.
We have been venturing into space for half a century, but there is still so much we don't know about how microgravity alters our bodies. But as we prepare for longer journeys to return humans to the Moon and possibly send them to Mars, it is now more imperative than ever to hone in on these effects — and find ways to mitigate them.
Perhaps no organ is more important to our future in space than our brains. But a new study, published Tuesday in the journal Radiology, reveals that long-duration spaceflight may fundamentally alter the amount of fluid in the brain. It could also affect brain volume, the results suggest.
These changes appear to last beyond the return to Earth — so the damage may be permanent.
How spaceflight changes the brain
For the study, the researchers took MRI brain scans of 11 astronauts (ten men and one woman) before and after they ventured into space onboard the ISS. The researchers then followed up with the astronauts at several intervals in the year after their return to Earth to see if there were any longterm effects.
The results show expansions in the astronauts' combined brain and cerebrospinal fluid volumes following their time in space. Cerebrospinal is the clear fluid that surrounds the brain and spinal cord, helping to protect them from shock.
The fluid volume increase remained a year after the astronauts' return to Earth.
"What we identified that no one has really identified before is that there is a significant increase of volume in the brain's white matter from preflight to postflight," Larry Kramer, from the University of Texas Health Science Center at Houston and lead author of the study, said in a statement.
"White matter expansion in fact is responsible for the largest increase in combined brain and cerebrospinal fluid volumes postflight."
The MRI scans also showed changes in the astronauts' pituitary glands. This is a pea-sized gland in the brain that regulates vital body functions because it controls most other hormone-secreting glands. The astronauts' pituitary gland appeared to have shrunk during their time in space, becoming both smaller in volume and shorter in length.
The researchers believe that these changes have to do with being in a microgravity environment. In this environment, gravity no longer acts to pull bodily fluids down, so instead fluids may redistribute towards astronauts' heads.
Microgravity's hidden toll — Previous studies suggest that spending lengthy periods in a microgravity environment can also take a toll on astronauts’ motor skills, cognitive abilities, and eye sight. All of these affects may be related to the change in fluid volume seen in this study's participants' brains.
So, what does this mean for humanity's plans to visit Mars? Thankfully, all hope is not lost.
It is important to note that one of the reasons why we don't yet know the full toll life in space might exact on the body and brain is because there simply isn't enough research out there to make any firm conclusions. Few of these kinds of studies have ever been conducted thus far, and there is an obvious shortage of subjects to participate in any that do happen.
At the same time, research like this doesn't just offer a gloomy prospect — it also opens the door to mitigating these effects. If scientists can work out what life in microgravity does and doesn't do to humans, then they can also perhaps work out how to prevent any negative consequences of spaceflight.
For example, the researchers behind this new study suggest creating a source of artificial gravity to help counter these brain changes, using a very large centrifuge, a machine used in labs that spins an object around a fixed axis thereby applying a strong force. But instead of putting test tubes in the centrifuge, they would put people, and it would force them into a sitting position.
These methods could also be applied on Earth for patients suffering from hydrocephalus, a condition where fluids accumulate in the brain, according to the researchers.
Astronauts on long-duration spaceflight missions may develop changes in ocular structure and function, which can persist for years after the return to normal gravity. Chronic exposure to elevated intracranial pressure during spaceflight is hypothesized to be a contributing factor, however, the etiologic causes remain unknown.
To investigate the intracranial effects of microgravity by measuring combined changes in intracranial volumetric parameters, pituitary morphologic structure, and aqueductal cerebrospinal fluid (CSF) hydrodynamics relative to spaceflight and to establish a comprehensive model of recovery after return to Earth.
Materials and Methods
This prospective longitudinal MRI study enrolled astronauts with planned long-duration spaceflight. Measures were conducted before spaceflight followed by 1, 30, 90, 180, and 360 days after landing. Intracranial volumetry and aqueductal CSF hydrodynamics (CSF peak-to-peak velocity amplitude and aqueductal stroke volume) were quantified for each phase. Qualitative and quantitative changes in pre- to postflight (day 1) pituitary morphologic structure were determined. Statistical analysis included separate mixed-effects models per dependent variable with repeated observations over time.
Eleven astronauts (mean age, 45 years ± 5 [standard deviation]; 10 men) showed increased mean volumes in the brain (28 mL; P < .001), white matter (26 mL; P < .001), mean lateral ventricles (2.2 mL; P < .001), and mean summated brain and CSF (33 mL; P < .001) at postflight day 1 with corresponding increases in mean aqueductal stroke volume (14.6 μL; P = .045) and mean CSF peak-to-peak velocity magnitude (2.2 cm/sec; P = .01). Summated mean brain and CSF volumes remained increased at 360 days after spaceflight (28 mL; P < .001). Qualitatively, six of 11 (55%) astronauts developed or showed exacerbated pituitary dome depression compared with baseline. Average midline pituitary height decreased from 5.9 to 5.3 mm (P < .001).
Long-duration spaceflight was associated with increased pituitary deformation, augmented aqueductal cerebrospinal fluid (CSF) hydrodynamics, and expansion of summated brain and CSF volumes. Summated brain and CSF volumetric expansion persisted up to 1 year into recovery, suggesting permanent alteration.