It’s not a study, but it’s been hypothesized that radiation and cosmic rays could cause lasting damage of just this sort through particle showers within the brain. Truthfully though there is very little in the way of studies for the simple fact that it’s hard to set one up for astronauts. Given how radically different the environment in space is compared to Earth though, I’m not finding this surprising. I wouldn’t be surprised if it’s just the tip of a very dangerous iceberg too, and it turns out that it takes a lot of time and sacrifice to get us to live and thrive somewhere other than Earth’s surface.

We have a small sample size of humans who have been exposed to space. I wonder what human mutations will be more preferable for space travel. Physical fitness is part of the equation but so is genetic-space compatibility.

Agreed. Genentic engineering will probably be helpful, but first we do as you say, have to know what to engineer for. Then of course we’ll have a kind of speciation event and we’ll risk having a kind of genetic apartheid based on people who work in space vs. planetside. It could get sci-fi dystopia levels of ugly if we don’t work to prevent those outcomes.

We already limit astronauts and many other professions based on genetic properties: height, tollerance to high g-forces, eyesight etc. Even things used as health indicators like resting blood pressure are influenced to a significant degree by genetics.

I think we will survive adding a few more genetic properties to the job requirements, especially since jobs on planets will vastly outnumber jobs in outer space for the forseeable future.

Sounds like Gattaca. It a very slippery slope when you start to genetically engineering people.

How do you engineer for space? Increasing telomere length is merely a stop-gap. Random mutations due to solar radiation are exactly the mechanism that evolution exploits to make progress (as well as other sources of entropy), the chemical makeup of DNA is poorly suited to space travel: you can't just genetically engineer that way.

You shorten the inter-generational period, i.e. make people breed rapidly (in space). The mutations will take of themselves.

Seems equally likely this is related to prolonged periods of relative isolation as much as being in space

They should have put the twin on earth in a simulates space station for a year. Also maybe the lack of bacterial biodiversity was a factor. I used to work analyzing DNA sequences of gut bacteria of MS patients. Surprisingly enough, bacteria affects many things about you, including cognitive performance.

I think the point of the study is to see the effects of space when compared to a normal life on Earth, not compared to a life on Earth in similar conditions.

I wonder if they've equally tested brain performance changes in low-stimulus environments such as an equally isolated cell in a prison on earth. Human senses exposed to variety of stimuli on earth may be keeping the brain more alert than what the space capsule offers.

Oh hey, I was a control for part of that (specifically, short term memory and mental math).

It's possible that he was still just tired after all that. I wouldn't read too far into a study with an N of 1.