Sci is about to embark on what she suspects will be two or three months with very little sleep, due to various personal and professional matters, and of course, blogging matters. And while she was discussing this with some friends, one of them brought up something very interesting:
She said “does anyone else feel COLD when they don’t get sleep?”
And it occurred to me that she was very right. When I haven’t been sleeping enough, I get COLD. I wake up freezing and end up bundling up in various thick, fuzzy sweatshirts and grasping on to mugs of hot coffee (though the coffee, of course, has a dual purpose). And so we started wondering, is this normal or anecdotal?
Being an awesome scientist herself, my friend hit the Pubmed, and a few moments later, she handed me this:
*pauses for a moment to put on fuzzy slippers*
Vaara et al. “The effect of 60-h sleep deprivation on cardiovascular regulation and body temperature”. European Journal of Applied Physiology, 2009.
For this study, the authors were interested to study the effects of sleep deprivation for problems like sustained military operations, and some sports events. Sci also thinks that the following study would have great application among college and graduate students, as she remembers (back when writing a very very important paper) staying up to the point where coffee literally made her sick (don’t try this at home).
Sleep deprivation is obviously not a very good thing, though most people in the US are hypothesized to live under a good degree of it most of the time (especially those of Sci’s acquaintance who are new parents). It has negative effects on cognition, as well as important effects on things like inflammation and the endocrine system ,and Sci has also heard of negative effects on the immune system. What the authors of this study were concerned with, however, was with heart problems (cardiovascular regulation) and with body temperature. The cardiovascular regulation part is important, for those who are both young and old, constant changes due to sleep deprivation could increase the risk of cardiovascular disease, something which most of us obviously do not need.
So for this study, the authors recruited male and female active cadets (they have 17 males and 3 females, I wish they would do this study in an all female population as well, I don’t think they got a big enough sampling) with strictly regimented normal activity and sleep times. They sleep deprived all of them for 60 hours (that’s 2.5 days) of what I’m sure was a rollicking good time. Sci would not want to do this study unless she was getting some hefty compensation. During the time they were sleep deprived, physical activity was restricted to a minimum, but they were still in the military, and so performed tactical stuff, while also being allowed to do things like read, play cards, or watch TV. And they were constantly watched to make sure they wouldn’t fall asleep (one hopes the experimenters were willing to go to great lengths to make sure the people didn’t fall asleep. Doing silly dances, maybe singing karaoke with them til the wee hours…).
During the sleep deprivation time, the scientists took measures of heart rate, blood pressure, and body temperature, as well as heart rate variability tests to look at differences in high frequency and low frequency power, which are supposed to reflect the influence of tone from the vagus, part of the sympathetic nervous system associated with drops in blood pressure and heart rate.
And they got some very pretty graphs.
Above you can see the measures of heart rate (the dashed line is sitting, the solid line is standing) during the three days of the study. You can see that heart rate in all the participants decreased significantly during sleep deprivation (Sci has anecdotally noticed the opposite effect, but suspects it’s due to the vast amounts of caffeine she has imbibed during her sleep deprivation sessions). But the question is whether or not this is due to changes in vagal tone (increased sympathetic involvement which can lower heart rate) or some other factor. So they then show this:
This is high frequency power taken during an active orthostatic test. In an orthostatic test (which you could actually try at home if you really wanted, though I don’t recommend doing it on 60 hours of sleep deprivation), you lay down for 15 min (without falling asleep), and record the pulse. Then stand up, and 15 SECONDS later record the pulse again. It’s usually used to determine if an athlete is overtraining, apparently a large difference between the two is supposed to be indicative, but Sci’s no expert on this topic. It appears here they are using it as a measure of vagal stimulation
And as you can see above that the high frequency power increased drastically over the three days of sleep deprivation, indicating an increase in vagal stimulation which could account for the DECREASE in heart rate seen above. Interestingly, though:
You can see here that blood pressure over the study didn’t change. As vagal stimulation causes decreases in heart rate AND blood pressure, Sci found this a little surprising, but it’s very possible that there are other factors at work keeping the blood pressure up (stress, for example), and other studies have also shown no changes in blood pressure in response to sleep deprivation.
But now we get to the figure that Sci was most interested in:
Here we have measures of body temperature taken over three days, and you can see that body temperature does indeed DROP during sleep deprivation (though circadian rhythms were apparently maintained). The authors hypothesize that this could be due to a stress response, ,and possible reductions in activity of the hypothalamus, a regulatory center of the brain which has strong impacts on both body temperature and heart rate, and which could be responsible for some of the effects.
So it’s true, you do indeed get a little colder (though you can relax, it’s only by half a degree C) as you get sleep deprived. A good reason to get some sleep! Not for Sci, though. Gotta get some work done. No wonder work gives me the chills!
Vaara, J., Kyröläinen, H., Koivu, M., Tulppo, M., & Finni, T. (2008). The effect of 60-h sleep deprivation on cardiovascular regulation and body temperature European Journal of Applied Physiology, 105 (3), 439-444 DOI: 10.1007/s00421-008-0921-5
Coffee making you sick… I once had hallucinations on coffee with heavy sleep deprivation. Along with the feverish size confusion (objects feel both minuscule and gargantuan at the same time, even though you know they’re neither).
Btw, for the feverish size confusion, I learned that I was not alone whose fever once spawned this monstruous concept. Has this fucked-upness ever produced a publication?
Mokawi, I’ve had hallucinations from heavy sleep deprivation without coffee.
In fact, with or without coffee, if you make it much past 60 hours with no sleep, and are not having hallucinations, you are very, very tough.
Does a fall in body temperature mean you are more likely to feel cold? I’m not sure about this. I’ve always thought that when the surrounding temperature remains constant, then the person with the lower body temperature would feel less cold, because of a lower difference with the surrounding temperature. Don’t cold receptors in the skin identify changes btw body and external temperatures?
I’ve always wondered if temperature changes mattered to make you feel different. I know when I’m really cold (like oh it’s -25 F wind chill yeah) I feel like all the bad parts of being drunk (or really sleep deprived).
But from my days of being very sleep deprived cold was bad for the first few days but after that other things took over like no balance, low brain power, and inability to tell what is actually funny (hey this is a big deal!). Stupid insomnia.
Accio: an interesting question. My understanding is that a small drop in body temp (1 degree C or so) results in shivering and a perception of BEING cold, accompanied by shivering and goosebumps. Dropping further than that dumps you into stage 2 hypothermia, which is often accompanied by a feeling of warmth even thought you’re shivering.
I believe that receptors for temperature are not changed by basal body temp, but respond only to changes in outside temp. I could be wrong, this isn’t my area of expertise.
Sara: sounds like stage 1 hypothermia right there, otherwise known as being really cold (danger is in stage 2 I think, though you should get warm if you’re in stage 1).
I can testify.
When I’m pulling long periods of being awake for 24+ hours, I go through a period every time at about 5-7a when I get the chills and cannot stop shivering regardless of the ambient temperature or how many sweaters I’m wearing. It’s also during this period that I’m most sleepy, and if I manage to stay awake out the other side I get a second wave and am good for about 14h of wakefulness. I’ve done this both in the lab and during marathon hacking sessions. I’ve also noticed that doing this successfully requires 4-5 meals.
However, when circumstances allow me to follow my innate circadian rhythms of going to bed about 9a and waking up at 3p, I don’t get the chills even in the middle of the night while I’m wide awake.
You noted that you desired coffee for both the warmth and the stimulatory effect. But is it not possible that the lowered body temperature is a way of allowing people to stay awake longer.
A lot of people, including the army, have noted that if your just a little bit cold you tend to not fall asleep. The discomfort of being cold tends to make staying awake easier. If you go too far you start to get hypothermic, and toward death, sleepy.
Many times I have stayed awake and helped myself stay awake by staying colder than I liked. Then when I could afford to sleep I warmed up and immediately fell asleep.
It seems reasonable that our ancestors had times when their ability to go without sleep was a survival bonus. Which raises the question of the roll of lowered body temperature. It is clearly a result of sleep deprivation. But is it just an unfortunate side effect or is it an adaptation left over from days when staying a little cold helped our ancestors stay awake and alive?
Strange, one thing I notice is that when I get tired, is that my ears get hot and glowing. It’s even so that when me and my brothers were kids my mother noticed by our red ears that it was time to go to bed, even though we insisted we were not tired at all.
Maybe that’s the cooling that needs to take place to get the body temperature lower?
That whole ‘cold keeps you awake’ thing is BULLSHIT. Total smelly bullshit. Or at least not universally applicable. Getting cold always makes me sleepy. I *hate* cold seminar rooms.
That said, being ‘comfortable’ but very slightly on the cold side is preferable to being comfortably toasty, when it comes to sleepiness while driving.
I think i had maybe no sleep but my nurse tells me…You had about 2 hours. This is very frequent. In my case just today I stayed on my back relaxing. She tells. i had 2 hours. Also in my case I believe it, I have been an insomniac for more than 50 years and I have had out of world experience,I look at myself
doing what I do. Don’t look for it!!
Another comment on the difference between feeling cold and being cold.
If hypothalamic down regulation (of the body’s thermostat) is the mechanism for the decrease on body temperature, it is unlikely that you will feel cold despite the reduction on body temperature. Patients with hypothalamic lesions may have temperatures in the low 30s deg C range yet not feel cold at all.
This paper doesn’t appear to answer the question “do you FEEL cold when sleep deprived?” or why – it just that you ARE cold.
Another one here who feels cold after 24 hours or so without sleep; and cold does put me to sleep, not keep me awake.
If lack of sleep depresses temperature, this has big implications for sleep-deprived women using temperature monitoring for fertility control.
This fits well with what I’ve heard about sleep deprivation being lethal if taken to extremes; apparently people “go cold and then they die.”
Holy crap, really!? Thank you! I always assumed I was crazy to feel cold after low/no sleep.
It /feels/ much more then .5 degrees C though. Like, I don’t shiver in 30 degrees in tank top/shorts, but I shiver in fuzzy blankets after no sleep different. Is there something else mucking up in our heads that makes it feel much worse then it is?
About 10 years back i was stranded on the night shift for 2 years and during that time my body temp fell from 1 to 2 degrees F (it varied). And I was always miserably cold. Though I no longer feel cold all the time, my mid afternoon resting body temp has never returned to my pre-night-shift normal.
Not so fast! There’s a difference between being colder and feeling colder. I am in my 50s and over the last several years my regular body temperature has dropped at least a whole degree from 98.6ish to 97.5ish. I don’t feel colder though. When you feel cold, isn’t your body trying to warm up?
Interesting – I also feel cold when I’m tired. It sets in about the same time as the grumpiness, leaving me a shivering, balled-up mess of aggravation.
Sleep deprivation can indeed give one the chills, and too many other physical and social miseries and limitations that you all are miserably experiencing. I’ve had insomnia since I was 13 years old. I know what it is to go two weeks without sleep and still show up for classes and then work, and motherhood. But the subject here is on the chills and sleeplessness. A few years ago, a master yoga teacher talked about the importance of being warm, for yoga, for sleep, for everything. I took his advice, and now it takes me as long to dress for bed as it does to go out. It’s important to keep the room cool to chilly – your preference. But dress for it. Don’t crank up the heat – it will only awaken you during the night. Wear a loose knit cap if your head is cold, wear loose cotton socks. Wear layers of blankets till you know what you need. The experiment is worth it. The nervous system will respond to your care and you’ll feel cared for by keeping yourself warm. We have to learn to put ourselves to bed. It’s important, too, not to get chilled during the day. Dress for weather, bundle up with layers, with scarves, gloves, hats, snug vests to keep the liver and kidneys warm. Avoid the chilblains during the day or you will probably have them at bedtime. Staying warm is not a panacea for insomnia in general. But who knows? Anyway, and lastly, despite claims by others, and usually by those who sleep like logs under all circumstances, I don’t know whether or not a hot or warm bath helps or hinders. Same for warm milk or a cup of chamomile. However, I myself wouldn’t dream of drinking coffee. I hope my advice has been worthwhile. Take care.
I’ve always found that it’s not the cold classroom that made me sleepy, but my response to the cold classroom: scrunching to as close to fetal-position as I could and resting my head against the desk when possible.
Also when I get sleepy in the car (I drive an hour every day and was working 12h shifts,) getting cold, quickly, was usually the best way to temporarily wake up. That and needing to pee.
(going off-topic)
@Mowaki: I experience the same size confusion whenever I get a measurable fever: tiny details feel _huge_ even when I know how tiny they are, and _I_ feel alternately over- or under-sized compared to my surroundings.
As a child this was actually quite frightening, as it probably should be since it’s a fever-induced hallucination. I can’t find any references to a similar phenomena, nor to your description. More recently I’ve tried to observe and influence it, and as I meditate to reduce my heart rate (and blood pressure with it) it lessens somewhat, but if I focus on an object, that object is the subject of tactile size confusion.
It frequently includes aural oversensitivity, and I recall a visual size confusion, but that may have simply been uncontrolled visual concentration (can’t look away) due to the tactile misperception.
Since it only happens when feverish and is affected by blood pressure and orientation, (being upright reduces it, but causes vertigo in its place,) it may simply be a part of the brain being squeezed wrong.
I wish I had the resources or background to study this, but alas I do not. Does anyone have references to this?
Actually, I get the same reaction after 3 or 4 nights of “vivid dreams” marathon (especially dreaming of running, climbing, swimming, flying and other physically demanding stuff). I wake up in the morning really tired and spend the day(s) under layers of warm stuff. Plus, it’s much easier for me to catch a cold then… That is really weird – seems like I’m having enough sleep, but the quality of this sleep almost equals not sleeping at all.
I once underwent six days without sleep (freshman finals at Princeton University). After 24 hours, my body temperature initially increased, albeit that perception is altered during sleep deprivation, as I suffered a heavy stream of hallucinations. Maybe I am an outlier, but nevertheless, immune response is surely triggered. However, I have read that different parts of the brain are used more heavily during sleep deprivation, which may be a benefit.