Length of REM Sleep Linked to Body Temperature

Summary: Study reports warm-blooded animals with higher body temperatures have lower amounts of REM sleep, while those with lower body temperatures have more REM sleep. Researchers say REM sleep acts like a “thermostatically controlled brain heater.”

Source: UCLA

Warm-blooded animal groups with higher body temperatures have lower amounts of rapid eye movement (REM) sleep, while those with lower body temperatures have more REM sleep, according to new research from UCLA professor Jerome Siegel, who said his study suggests that REM sleep acts like a “thermostatically controlled brain heater.”  

The study in Lancet Neurology suggests a previously unobserved relationship between body temperature and REM sleep, a period of sleep when the brain is highly active, said Siegel, who directs the Center for Sleep Research at the Jane and Terry Semel Institute for Neuroscience and Human Behavior at UCLA. 

Birds have the highest body temperature of any warm-blooded, or homeotherm, animal group at 41 degrees while getting the least REM sleep at 0.7 hours per day. That’s followed by humans and other placental mammals (37 degrees, 2 hours of REM sleep), marsupials (35 degrees, 4.4 hours of REM sleep), and monotremes (31 degrees, 7.5 hours of REM sleep). 

This shows a woman sleeping
Brain temperature falls in non-REM sleep and then rises in REM sleep that typically follows. Image is in the public domain

Brain temperature falls in non-REM sleep and then rises in REM sleep that typically follows. This pattern “allows homeotherm mammals to save energy in non-REM sleep without the brain getting so cold that it is unresponsive to threat,” Siegel said.  

The amount of humans’ REM sleep is neither high nor low compared to other homeotherm animals, “undermining some popular views suggesting a role for REM sleep in learning or emotional regulation,” he said.  

Funding: Siegel’s research is supported by National Institutes of Health grants (HLB148574 and DA034748) and the Medical Research Service of the Department of Veterans Affairs. He declared no competing interests.  

About this sleep research news

Author: Jason Millman
Source: UCLA
Contact: Jason Millman – UCLA
Image: The image is in the public domain

Original Research: Open access.
Sleep function: an evolutionary perspective” by  Jerome Siegel et al. Lancet Neurology


Sleep function: an evolutionary perspective

Prospective epidemiological studies in industrial societies indicate that 7 h of sleep per night in people aged 18 years or older is optimum, with higher and lower amounts of sleep predicting a shorter lifespan. Humans living a hunter-gatherer lifestyle (eg, tribal groups) sleep for 6–8 h per night, with the longest sleep durations in winter.

The prevalence of insomnia in hunter-gatherer populations is low (around 2%) compared with the prevalence of insomnia in industrial societies (around 10–30%). Sleep deprivation studies, which are done to gain insights into sleep function, are often confounded by the effects of stress.

Consideration of the duration of spontaneous daily sleep across species of mammals, which ranges from 2 h to 20 h, can provide important insights into sleep function without the stress of deprivation.

Sleep duration is not related to brain size or cognitive ability. Rather, sleep duration across species is associated with their ecological niche and feeding requirements, indicating a role for wake–sleep balance in food acquisition and energy conservation. Brain temperature drops from waking levels during non-rapid eye movement (non-REM) sleep and rises during REM sleep.

Average daily REM sleep time of homeotherm orders is negatively correlated with average body and brain temperature, with the largest amount of REM sleep in egg laying (monotreme) mammals, moderate amounts in pouched (marsupial) mammals, lower amounts in placental mammals, and the lowest amounts in birds.

REM sleep might, therefore, have a key role in the regulation of temperature and metabolism of the brain during sleep and in the facilitation of alert awakening.

Join our Newsletter
I agree to have my personal information transferred to AWeber for Neuroscience Newsletter ( more information )
Sign up to receive our recent neuroscience headlines and summaries sent to your email once a day, totally free.
We hate spam and only use your email to contact you about newsletters. You can cancel your subscription any time.
  1. I’m sleep deprived.Seven years ago I had nasty gut bacteria helicobacter.pylori which screwed my sleep cycle to only three hours a night.I woke up with nightmares.That lasted for two hell of a months.I also took beta blocator and I skipped dinner,by gastroenterologyst advice.It was hell day and night,anxiety attacks,panic and my family members guilt was on top of it.Both parents histerical narcisists.My own told me I want to be sick,and he put oil on fire,as much as he could.Then after two months,I visited neurologyst.She prescribed me antidepresant abd two more meds.I could sleep,but still was a zombie for next 10 months.How I solved it.I had read beta blocators lowers blood pressure,so I quit with it.I started with yoga,then pushups,pullups,and not skipping dinner anymore.I got well from innate to doctors,and people who humiliated me during severe deoression period.Now I sleep three hours naturaly,and then I taje 1mg of antidepresant to get deep sleep and those 4-5hours.With healthy food,exercises in moderation,avoiding everything which bothers guthealth,so less sugar,less salty food,no coffee,no alcohol I became stronger and I look 10 years younger.I indulge in to unhealthy food during holidays,weddings.I fix gut problems with probiotic supplements or probiotic yogurt.I play basketball even U’m 46yo,go for running,swimming,fast walking.Unfortunately I will never have those 8 hours,like most people have,but I function great when I’m not hungry and when I have enough of sleep.Without coffee it id hard during day,less motivated more sleepy.At night I am energetic by nature and I can hear sounds above average human.I tried to work as hardworker to exhaust my body,but brain is active at night since I screwed up my sleeping cycle,after burnout.Hope this bad experience will help somebody,it is sad,pathetic,toxic but there is happy end.For last 6 years I dont remember when I was sick,Ijust go to doctor to prescribe me antidepresants for deeper sleep💪😇

Comments are closed.