What Happens To An Astronauts Body Temperature During A Long Space Flight?
Today lets talk about astronauts! More specifically an important aspect of an astronauts physiology during a long mission out in space, their body temperature. Furthermore lets center our discussion around an article published in the journal Nature: Scientific Reports titled "Increased core body temperature in astronauts during long-duration space missions".
What Do Ya Know About Body Temp?
I am going to take a guess and say that body temperature isn't something you normally think about ( I know when I roll out of bed in the morning... my body temperature isn't exactly the first thing on my mind... its usually the thought "Damn it, morning already?" ). We don't NEED to think about it much, since since temperature is pretty well regulated after all, especially here on earth with our great atmosphere! So perhaps lets begin by discussing it just a bit.
You are all familiar with just how important our body temperature is to how we feel right? You know that the average human body temperature is 37 °C and we've likely all been sick and had a slightly elevated temperature and felt awful, or been outside unprepared in the winter and experienced a slightly lowered body temperature (the beginnings of hypothermia).
Maintaining a body temperature right around that 37 °C mark is extremely important for a variety of things including our abilities to accomplish both physical or mental tasks (AKA, its important for literally every aspect of our existence!). [2], [3]. If our body temperatures get too high, or too low... well you know the result... (gulp) death.
So how do we achieve this very specific body temperature? Well a portion of the brain called the hypothalamus does the heavy lifting for you. It causes us to give off less heat when our body temperatures drift too low, and to further give off more heat and utilize the exaporation of sweat to cool things down when it drifts too high. [4] It is recommended that for any worker, doing a job that their core body temperature not exceed 38 °C, so we really only have a 1 °C window.
On earth our atmosphere does a good job allowing for effective heat transfer, however in space things are a bit different for the astronauts. In fact there is another contributing factor to effective transfer of heat away from our bodies that we on earth all take for granted.
Gravity
Up in space there is a distinct lack of gravity, and the result is a recipe for reduced heat transfer away from the body (evaporation of sweat... not so easy in zero gravity!) [5] However, does this reduced heat transfer ability actually cause drastic changes to astronauts core body temperatures?
The Data
Okay so this study was simple enough to perform, just monitor the body temperature of astronauts on long space flight missions on a daily basis. Which is precisely what was done:
In the image to the left we are looking at reported core body temperature (CBT) readings for the astronauts. Pre, is the value prior to the initiation of the space flight (the greyed box), and the values after the greyed box (+1 etc) are days back on earth after the space mission. What we can see from this figure is that the astronauts core body temperature, at rest, was raised by around 1 °C after by 75 days of space flight (so a good length for a mission). This is within the recommended guidelines for people who are actively engaged in work on earth and likely does not pose a significant health risk. (three *'s above the data point indicates a p<0.001, so relatively good statistical significance that the rise is indeed a real phenomenon and not due to just noise in the data). We also see in this data that upon returning to earth, the astronauts body temperature quickly returns to the pre-mission levels.
In the image to the right, we are looking at reported core body temperature readings for the astronauts during exercise. We can see that while still on earth, during exercise the astronauts body temperatures increased by about 1.5 °C from at rest levels, and that exercising in space resulted in a significant further increase in the body temperatures, with some astronauts reporting core body temperature readings exceeding 40 °C, which would be a 3 °C or greater increase. To make matters worse, the intensity of the exercise the astronauts were doing during the space fight was significantly lower then what was done for the "pre-flight" baseline.
This is a bit troubling, as it has been determined elsewhere that [6] exposure of the brain to temperatures of 44 °C can cause lasting damage, and these astronauts were pushing values exceeding 40 °C with out even working as hard as they could be! This means its a potential that the astronauts could experience body temperatures that were far too high quite easily.
TL;DR
Our body temperatures are highly regulated, with an optimal temperature of around 37 °C. Here the authors report that regulation of body temperatures is much more difficult in outer space based on data collected from astronauts during space flight. An increase in body temperature was observed both during activity in space and also during rest. As such the authors have coined the term "space fever" to describe the phenomenon. The increased body temperatures that astronauts are experiencing have the potential to cause health issues that may remain even after they are no longer participating in space flights. So the question we are left with now is... what do we do with this information? How can we better protect our astronauts bodies during space flights?
Sources
Image Sources
Text Sources
- https://www.nature.com/articles/s41598-017-15560-w
- http://journals.sagepub.com/doi/10.1518/001872007X230226
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4701920/
- http://jap.physiology.org/content/100/6/2065
- https://www.ncbi.nlm.nih.gov/pubmed/11669102
- http://www.sciencedirect.com/science/article/pii/S0301008204000437
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This is a very interesting study, thank you for bringing this article to light! It makes me think that the lack of gravity coupled with the surface tension of water makes it harder for sweat to escape skin pores to the surface so that evaporation can take place.
I was also wondering about the ambient air temperature and what influence that might have on the ability of the body to cool by reaching an equilibrium. In the methods section of the study, they describe how the average air temperature in space was 23.6 degrees, compared the the 21.0 degree average for the earth baseline tests before and after flight.
This difference may be part of the reason for the increase in both resting and exercise temperature in space - the warmer environment in space means that heat is removed less rapidly by the skin equilibrating with the air temperature. The influence of this could easily be tested by running the earth-based experiments with the same average air temperature that is observed in the space-based measurements. It would also be nice to see a larger sample size where differences between genders could be considered. I guess this is an argument for further research into the subject!
Edit: I made an overlay from the included figure that normalizes the baseline temperature of resting and exercise to the pre-flight data point. This makes it a little easier to compare the differences between the two plots and see how space exercise causes a slight elevation in body temperature relative to the baseline.
Certainly may be a contributing factor, though in that case why would the CBT continue to rise over the course of 75 days in space? On earth our CBT is fairly well regulated regardless of a 2 C change in ambient temperature.
There definitely seems to be something strange going on during spaceflight beyond just the ambient air temperature. It would be interesting to see measurements of the ambient air on the days of the experiment to see how strong the correlation between the increases and decreases are. The variability of average temperature in space was +- 1.8 degrees, while the earth measurements were +- 1.2 degrees. It is confusing why the temperature CBT would only increase for the first 75 days and then drop off...I hope to see some follow up studies on this topic that might help to answer all of these remaining questions!
Indeed, me as well.
Great post. Now that space fever is an actual thing I'm going to start using the term daily. One question though, why is the evaporation of sweat harder in zero gravity?
Perhaps evaporation isn't the right term to use, maybe dissipation? In zero gravity both heat and moisture stay in place, where as here things would dissipate away in the air. Zero gravity makes it more difficult for the heat to get away from the astronauts body.
Ah, makes more sense now. Thanks for the explanation.
Fascinating review. Sauna use for health has gotten a lot of attention in recent years. Dr. Rhonda Patrick, an authority in anti aging, speaks highly of sauna use for it ability to stimulate heat shock proteins in the body. These proteins are supposed to be beneficial to our health in a plethora of ways.
It's incredible to see how acutely elevated body temp is beneficial, while Chronically high body temperature is detrimental.
It goes back to that old saying: too much of anything is bad.
Our Biochemistry is immensely complicated indeed.
I really think about temperature when I wake up: "damned, it is much warmer and better under the blanket" ^^
Interesting article by the way. I never thought about this. The lack of gravity may also change the maximum temperature the body can cope with, I guess. I can imagine that all we know has been done measured on Earth.
It seems like there just isn't a lot of information on this from space yeah. The article talks about anecdotal reports from astronauts about being too hot during space flight, so it sounds like they weren't surprised by the data. However I can say that I was.
I was actually more shocked by the magnitude of the difference. I guess that with space being trendy those days, the amount of data will increase. It is thus enough to stay tuned ^^
As usual another great read from you mate! This is really crazy that nearly all of us never really worry of our body temperature...and in fact this is super important for us to live well!
I hope we get the solution to help those astronauts as it will not be great seeing these people getting all types of sickness afterwards.
Me too! It's amazing how many different things we have to try to account for with space flight. I never really thought about how body temperature might be affected. It's a shame it seems to make it so much harder for the astronauts bodies to regulate.
I was following closely the case of Scott Kelly after his full year in space, but then I just got busy and forgot about it! Your post made me really excited to go make some research about it and what happened.
https://www.theverge.com/2017/10/28/16549898/scott-kelly-pbs-exclusive-clip-year-in-space-walking-problems-zero-gravity
Thanks for the link my friend! Scary thing when I saw him struggling to walk properly in the first hours!
We can say he sacrificed himself to help do studies and find solutions.
I read your "... (gulp) death" in Shaggy's (Scooby-Doo) voice. There wasn't a point in telling you this, but I thought it was funny and figured I'd share.
This was interesting, thank you! I had always figured that the onboard fans were calibrated to both keep the temperature at a safe level and move the air in the compartments. (You know what they say about assuming.) After reading your post, I went looking and found that the astronauts will try to get close to a fan so they can cool down. Also, I learned that the 1 degree of temperature change effects the amount of rations that the astronauts consume. That probably means that before researchers started studying the temperature change, not only were these poor astronauts uncomfortably warm, they also didn't have a sufficient amount of food provided to them. 😟
You mentioned that when they return to Earth the astronauts' temperatures quickly return to normal. When they land, do the astronauts have to take steps to make sure that the adjustment doesn't happen too quickly?
This is a good question, but unfortunately I do not know the answer!
Very nice post i liked reading it
I'm glad you enjoyed it. Thanks for reading.
Really interesting post. I'm usually not too into science, personally it's one of my weaker subjects, but your post kept me interested to the end. I had no idea that their temperatures would go up-- for some reason I assumed they'd get colder! I was wrong. Thanks for the informational post though!
You are welcome. I think that people don't like science because the world does a crappy job explaining things. Either the material is too text book like, or the content not appropriately broken down. Teachers uninterested in the material don't help get their students excited in it either.
Research is full of all sorts of unexpected results like the one I discussed above. I think more people would get excited if they heard about them!
Thanks for reading, glad you enjoyed the post. I was also surprised by the findings. :)
The data which you had shown with us about the body temperature of astronomers who work on space mission. Really put them risk and they are really doing great. It may cause them some serious issues all the information given by you is really very new for me and at same time now I have a great respect for all astronomers.
Yep! It indicates that we need to do more to try to protect their health while they are on space missions.
Yes sir because all the space mission and satellites are regulated by then and if we lose any one of them it's a huge damage for our experience astronomers.
Hey my friend you had really shows a very great information and some of the unknown facts to us about body temperature in space and what are the other problems faced by them. Well I must appreciate your post because of you have done a lot of work to create this.
Thanks for giving it a read. :) Glad you liked it.
Thank you for your great response over my comment.