Sleep deprivation in spaceflight

[Ivan Seeking]

Numerous anecdotes in the past suggest the concept that sleep disturbances in astronauts occur more frequently during spaceflight than on ground. Such disturbances may be caused in part by exogenous factors, but also an altered physiological state under microgravity may add to reducing sleep quality in a spacecraft . The present investigation aims at a better understanding of possible sleep disturbances under microgravity. [continued]

http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=9125693&dopt=AbstractPlus

This paper is linked only to reference the question: Why do astronauts tend to sleep less while in space?

It is [apparently] still an unsolved problem, and it sounded interesting.

 

[Dale]

I sleep less whenever I travel a few hundered miles. I am not surprised that they sleep less when they travel thousands or millions of miles.

What makes this surprising/interesting?

 

[Ivan Seeking]

I sleep less whenever I travel a few hundered miles. I am not surprised that they sleep less when they travel thousands or millions of miles.

What makes this surprising/interesting?

Its a problem for NASA because sleep deprived astronauts are dangerous. The reason why this happens is not understood, which is why it is being studied. The idea that we might expect this based on other examples does not imply that we understand it.

 

[Dale]

Well, if they can understand and fix it for astronauts, maybe they can fix it for business travelers too. That would certainly improve my life!

 

[Moonbear]

The point is that the reasons for the sleep disturbances may not be the same in space as on Earth. On Earth, we have a pretty good handle on the cause, and that's the shift in daylight hours. After about a week, you've adjusted to the new schedule, and all is fine. What they are saying is that on the space station, they aren't adjusting to the light schedule. Though, I wonder how consistent they are about the lighting schedule on the space station.

 

[Ivan Seeking]

The point is that the reasons for the sleep disturbances may not be the same in space as on Earth. On Earth, we have a pretty good handle on the cause, and that's the shift in daylight hours. After about a week, you've adjusted to the new schedule, and all is fine. What they are saying is that on the space station, they aren't adjusting to the light schedule. Though, I wonder how consistent they are about the lighting schedule on the space station.

The comments made by one NASA scientist was that over time, some astronauts can reach a point where they are only sleeping 4 hours a night. But it wasn't clear if this happens as smooth function of time or in a stepwise fashion.

 

[Far Star]

If this phenomena hasn't been noted in other research environments (submarines, caves) I'd be inclined to consider sound as a possible factor.

 

[Moonbear]

If this phenomena hasn't been noted in other research environments (submarines, caves) I'd be inclined to consider sound as a possible factor.

I'm not sure what experiments you're referring to regarding subs; can you referece those? I assume by the cave example you're talking about those who were entirely deprived of daylength cues? In those cases, a free running rhythm develops. I can't get the whole article that Ivan posted, but from the abstract, they are saying that a free-running rhythm was not occurring. The only other thing that comes to mind is if they use a different type of light on the space station than standard fluorescent or incandescent bulbs used in lab conditions (usually fluorescent tubes). Perhaps something about the light spectrum they are exposed to is making a difference.

 

[Far Star]

I'm not sure what experiments you're referring to regarding subs; can you referece those? I assume by the cave example you're talking about those who were entirely deprived of daylength cues? In those cases, a free running rhythm develops. I can't get the whole article that Ivan posted, but from the abstract, they are saying that a free-running rhythm was not occurring. The only other thing that comes to mind is if they use a different type of light on the space station than standard fluorescent or incandescent bulbs used in lab conditions (usually fluorescent tubes). Perhaps something about the light spectrum they are exposed to is making a difference.

I haven't delved into sub studies but it seems logical to think someone would have noticed a change in sleep pattern if it were common among those spending months under artificial light. It would be handy to know if they've also noticed a similar effect on other mammals in a space environment. I'd also question what type of continuous vibration they might be subject to in relation to space vs earth. It could very well be the type of light source as well. As usual, more questions than answers given a snippet of information.

 

[Moonbear]

I haven't delved into sub studies but it seems logical to think someone would have noticed a change in sleep pattern if it were common among those spending months under artificial light.

Oh, the emphasis was on the IF in your post. Sorry, it wasn't clear. I thought you knew of some study.

 

[Far Star]

Detail on space studies:

http://ajpregu.physiology.org/cgi/content/full/281/5/R1647

 

[Evo]

This paper is linked only to reference the question: Why do astronauts tend to sleep less while in space?

No gravity? Odd, cramped quarters, odd food, odd way of evacuating bowels and urine, confinement, must be some underlying tensions, even if they keep it under control, excitement of where they are. Heck, anyone one of those would be more likely to keep me from sleeping than the lighting.

 

[Spirochete]

I haven't delved into sub studies but it seems logical to think someone would have noticed a change in sleep pattern if it were common among those spending months under artificial light. It would be handy to know if they've also noticed a similar effect on other mammals in a space environment. I'd also question what type of continuous vibration they might be subject to in relation to space vs earth. It could very well be the type of light source as well. As usual, more questions than answers given a snippet of information.

Not sure how related this is, but. . .

A while ago (a couple of decades maybe) a professor and a grad student spent over a month in a cave. The goal of the experiment was to determine what sleep pattern they'd fall into in the absence of both light and also in the absence of societal pressure to conform to a "normal" sleep schedule. The professor fell into a regular pattern where he slept 8 hours at a time. The grad student eventually began sleeping for only four hours at a time. However he also was awake for shorter periods of time, maybe 7 hours total before sleeping again. So he ended up with the same amount of sleep as the professor.

The conclusion of the study was "people naturally sleep 8 hours a night, society was right all along." Considering the size of the study, this was obviously not a statistically valid conclusion to reach.

If anybody knows the name of the study author I'd be interested.

 

[Moonbear]

Not sure how related this is, but. . .

A while ago (a couple of decades maybe) a professor and a grad student spent over a month in a cave. The goal of the experiment was to determine what sleep pattern they'd fall into in the absence of both light and also in the absence of societal pressure to conform to a "normal" sleep schedule. The professor fell into a regular pattern where he slept 8 hours at a time. The grad student eventually began sleeping for only four hours at a time. However he also was awake for shorter periods of time, maybe 7 hours total before sleeping again. So he ended up with the same amount of sleep as the professor.

The conclusion of the study was "people naturally sleep 8 hours a night, society was right all along." Considering the size of the study, this was obviously not a statistically valid conclusion to reach.

If anybody knows the name of the study author I'd be interested.

I don't know that specific study, but there have been others like it, and it's consistent with animal studies. What that is describing is what is termed a "free running rhythm." In other words, the timing is not synchronized to any environmental cues (i.e., sunrise/sunset) nor to others in the group. Everyone sleeps roughly the same amount, but not at the same time or not in any regular pattern. You'll see the same types of patterns (or lack thereof) in heart rate, food intake, body temperature, activity patterns. It becomes very disorganized.

If I understand Ivan's post correctly, they're saying this isn't happening. But, maybe it's a misunderstanding of the astronauts or those reporting this of what a free running rhythm is. If they're sleeping 4 hours, awake 8 hours, sleeping 4 hours, etc., that would be indicative of a free running rhythm. Because there may be social cues among the other astronauts, it's also possible there is a masking of the true free running pattern by a certain degree of synchrony among the astronauts. For example, if one person might sleep longer, but the one who wakes up after 4 hours makes enough noise to wake everyone, that would be considered "masking" of the real rhythm of the person who sleeps longer if left undisturbed.

Without looking at a long term chart of their activity or sleep/wake patterns, it's hard to know what's really happening.