A new study has shown that spending long periods of time is not advisable as it not only leads to muscle atrophy and reductions in bone density but it could have long last negative effects on the brain.
According to the study by Ludwig Maximilian University of Munich (LMU) that was carried out in Russian cosmonauts there are differential changes in the three main tissue volumes of the brain remain detectable for at least half a year after the end of their last mission.
It remains unclear whether and to what extent the neuroanatomical changes so far observed persist following return to normal gravity, they said.
The study was carried out on ten cosmonauts, each of whom had spent an average of 189 days on board the International Space Station (ISS). The researchers used magnetic resonance tomography (MRT) to image the brains of the subjects both before and shortly after the conclusion of their long-term missions.
In addition, seven members of the cohort were re-examined seven months after their return from space.
The MRT scans performed in the days after the return to Earth revealed that the volume of the grey matter (the part of the cerebral cortex that mainly consists of the cell bodies of the neurons) was reduced compared to the baseline measurement before launch. In the follow-up scans done 7 months later, this effect was partly reversed, but nevertheless still detectable.
In contrast, the volume of the cerebrospinal fluid, which fills the inner and outer cavities of the brain, increased within the cortex during long-term exposure to microgravity.
Moreover, this process was also observable in the outside spaces that cover the brain after the return to Earth, while the cerebrospinal fluid spaces within returned to near normal size.
The white matter tissue volume (those parts of the brain that are primarily made up of nerve fibres) appeared to be unchanged upon investigation immediately after landing.
However, the subsequent examination 6 months later showed a widespread reduction in volume relative to both earlier measurements.
In this case, the researchers postulate that over the course of a longer stint in space, the volume of the white matter may slowly be replaced by an influx of cerebrospinal fluid.
Upon return to Earth, this process is then gradually reversed, which then results in a relative reduction of white matter volume.