By Oktay Ozadam
Just about everyone is aware that their temperature fluctuates while sleeping, but probably not everyone knows why that is exactly.
From thermoregulation to the circadian rhythm, let's take a deep dive into your body's nighttime temperature and how regulating it can result in a more well-rested and restorative sleep.
How does Circadian Rhythm Affect Body Temperature?
When light enters our eyes, there is a part of our brain called the suprachiasmatic nucleus (mercifully abbreviated to 'SCN'), which triggers neural signals that control our internal temperature. As evening comes around and the sun begins to set the SCN begins to signal our body to begin cooling down.
Note: This is one of the reasons you are not supposed to stare at your phone before bed. When your brain processes the light from your phone, your brain is processing light when it shouldn't be!
The Connection Between Light and Temperature
The circadian rhythm is our twenty-four-hour sleep/wake cycle, and it is intimately connected with the small temperature fluctuations that we all experience as a result of how our bodies respond to light. We cool down by a few degrees as we sleep in order for our heart rate, respiratory rate, and organs to slow.
Consider the caveman
Our body knows to begin cooling and slowing as a result of us seeing less light as day turns to night. If you imagine our caveman ancestors, nighttime is an ideal time to recharge and regain energy, considering they couldn't hunt or farm without light. This response to night and day is one of the most fundamental aspects of our circadian rhythm.
Does Body Temperature Drop or Rise When You Sleep?
Your body temperature drops by a couple of degrees as you sleep. It fluctuates slightly within this colder range in the same way it does while you're awake and warmer.
In the late afternoon, your body will begin to cool somewhat to prepare itself for sleep. You are then at your coldest about two hours before you wake up. After that, you gradually begin to warm up again as your body prepares you for the day.
Not too hot. Not too cold.
As a result of the natural cooling process we experience daily, setting your thermostat at night within the range of 60° F (15° C) and 67° F (19° C) can help facilitate this drop in your body temperature and can result in a more restful night.
What are Some Signs of not Getting Enough Sleep?
Your nighttime temperature is very closely related to your quality of sleep. It may be difficult to know whether you are snoozing to your fullest if you're gauging that by how you feel during the day. On some days you may feel right as rain, and on others, there is not enough coffee in the world to keep you awake!
Let's take a quick look at some of the signs of low-quality, or restless sleep:
- Your Eyes.
- Caffeine Compensation.
- Trouble Focusing.
- Increased Acne.
- Weight Gain.
Redness, puffiness, dark circles, or bags around your eyes are indicators of not getting enough sleep. This is likely because your body produces a hormone in deep sleep that aids in rejuvenating tissue repair.
In the United States, about eighty-three percent of people consume coffee on a regular basis. Coffee has a whole host of health benefits, but an unhealthy dependence can be an indication that you're not sleeping well. If you need caffeine to stay awake, you may need to consider some of the ways outlined in this article to improve your sleep quality.
If your thinking is foggy or you have trouble focusing, you may not be giving your brain enough of a break at night. Moodiness, depression, and irritability are a few other indicators of sleep deprivation.
If you're noticing more breakouts, it could be because a lack of sleep not only hurts the immune system but causes imbalances in your hormones, which can result in breakouts.
Ghrelin and leptin are two hormones that control how hungry you feel. Under the conditions of sleep deprivation, your body is unable to control these hormones properly. This might make you feel like having an extra snack or two during the day, which can cause weight gain.
The laundry list of physical and mental issues associated with sleep-deprivation can seem daunting. Although your issue may be a deeper one requiring medical assistance (such as sleep apnea or acid reflux), taking a look at the temperature you sleep at could be a quick fix to a pervasive problem.
How Does Thermoregulation Work in the Human Body?
Thermoregulation is a process by which our body regulates its temperature. This regulation is essential for a whole host of reasons, but as it relates to sleep, it is essential that our body warms and cools in conjunction with sunlight.
We are equipped with the ability to know when to sleep in a sophisticated way that goes beyond just feeling tired. If the lights go out, a process that starts in our brains will begin where we gradually start to cool in order to prepare for rest.
A balancing act
Our bodies naturally want to achieve stable homeostasis between 98°F (37°C) and 100°F (37.8°C). During sleep, our core temperature is on the lower end of that spectrum while during wakefulness, we are slightly warmer.
What Happens to Body Temperature During REM Sleep?
During REM sleep (also referred to as deep sleep), the cells within our brains that regulate temperature actually turn off. Our body's temperature is then regulated by the temperature within our beds and bedrooms. Oddly enough, humans become temporarily cold-blooded during REM sleep!
At the mercy of our environmental temperature
This occurrence during REM sleep may seem odd, considering that the processes that maintain our internal temperature seem so carefully calibrated. A bedroom that is too warm or cold can cause you to wake up from deep sleep sweating or shivering due to our susceptibility to the temperature of our environment during REM sleep.
Typically, your first REM cycle begins about ninety minutes after you fall asleep and will last for only about ten minutes. Each subsequent cycle gets longer with your longest being your final cycle that occurs toward the morning and can last up to an hour.
Side note: Deep sleep is also when we have our most vivid dreams, and when our sleeping brain is most active. Many experts suggest we have anywhere between four and six distinctive dreams per night. Although, after waking up, many people tend to only remember fragments.
Can You Change Body Temperature During a Sleep Cycle?
It is both possible and wise to regulate your body temperature during the night. Our bodies do have a natural nighttime routine, but we can aid that routine by changing the temperature of our environments, and thus our bodies.
Not only is this helpful because of your personal comfort, but as previously mentioned, our bodies have some unique functions while we sleep.
- Thermoregulation is the system our body uses to warm and cool itself and works very closely with our circadian rhythms. Although our systems work well on their own, we can externally aid these processes.
- Our body temperature is susceptible to the temperature of our environment, especially during REM sleep, which constitutes roughly twenty-five percent of our night.
Gizmos, gadgets, and a better night's sleep
There have been several incredible gadgets developed to aid in maintaining an optimal sleep temperature, and thousands of people have reported that they work wonders. These include fans that gently blow air under your covers like the Bedjet cooling system and bFan cooling fan.
There are also very comfortable mats you can sleep on like the chiliPAD (read the review in full here) or Kryo(OOLER) Sleep System which work on a thermostat. Another fantastic option is a thermoregulated pillow pad like the Moona Pillow that solves the common but dreaded issue of your pillow being too hot.
If you'd like to read more about the best bed cooling and heating gadgets for a more restorative night's sleep, check out this article, which takes a deeper dive into how bed cooling products work and how they perform.
How Does Body Temperature Changes During the Day?
Your body operates on a sophisticated clock based around daylight. At around 5 AM or roughly two hours before waking, you will start to warm up one to two degrees from your colder sleep temperature. Then during the late afternoon, your temperature will start to gradually decline back down into the lower temperatures in order to prepare you for sleep once again.
Whether awake or sleeping, your body temperature does fluctuate slightly depending on factors like activity, but while sleeping, those fluctuations occur at a slightly colder register.
What is Core Body Temperature?
Your core body temperature is at a reasonably stable 98.6°F (37.7°C). This homeostatic temperature is regulated by our internal systems that monitor and adjust our temperature.
What is Normal Ideal Body Temperature While Sleeping?
Since we sleep one to two degrees cooler than when we are awake, helping your body regulate its temperature can help facilitate better sleep by aiding the natural process of cooling down as we rest. It is traditionally agreed upon that the best temperature to sleep at in order to give your body a boost is between 60° F (15° C) and 67° F (19° C) for most people and 65° F (18° C) and 70° F (21° C) for the elderly or infants.
For a more in-depth look at the science and logic behind this specific temperature range take a look at our article that looks into the Best Temperature for Sleep.
Why Does Your Body Get Hot When You Sleep?
Despite the fact that your body actually cools while you sleep, there are several reasons why you may feel hot or wake up too warm. This includes common sense explanations such as your thermostat being a tad too high. There are some less obvious and more technical reasons, though, such as a higher metabolic rate or the lack of thermoregulation during REM sleep.
Although it may not be your cause, sleeping hot can be a symptom of some serious medical issues. Let's take a look at those and a few other possible causes:
- Menopause – Hot flashes are a widespread and natural cause of night sweats for women. Changes in your diet or doctor-approved hormonal therapy can help alleviate some of the symptoms that cause this uncomfortable hot feeling. Additionally, several of the products mentioned above can provide a great deal of relief.
- Idiopathic hyperhidrosis – This condition causes the body to produce an excess of sweat without any medically identifiable reason.
- Exercise before bed – A cool-down sessions a few hours before bed can be a significant help in lowering your body temperature before sleep. A great alternative to exercising before bed is stretching, or yoga, which helps you to relax while still contributing to your fitness routine.
- A dense foam mat/pad – These bed toppers may be very comfortable, but they are not particularly breathable. An issue easily remedied by one of the temperature-regulating devices mentioned above.
- Low blood sugar – Hypoglycemic Individuals may experience more sweating while taking insulin.
- Cancers – Night sweats can be a symptom of several cancers, the most common being lymphoma. Generally, however, those with undiagnosed cancer will likely experience additional symptoms such as a fever or unexplained weight loss.
- Hormone disorders – Several of these disorders can result in night sweats. One indicator of hormonal problems is red or flushed skin.
- Neurological conditions - This is unusual, but a select few neurological disorders can contribute to night sweats and feeling too warm while sleeping.
The most common and likely reason is that your bed or room is too warm. Since your body releases a lot of heat into your surrounding area, if you're covered in blankets or dressed too warmly, it's very likely you will wake up hot at some point during the night.
As tempting as it is to get all bundled up and toasty before bed, you may be doing yourself a disservice!
Our bodies are very complex systems, and science is still unraveling all the little aspects that we take for granted day-to-day. Despite how complex we are, there are several principles that have been uncovered that can help you sleep better.
Some subtle changes to your sleeping habits can have a considerable impact on your overall health. Now that you are in-the-know about some of the finer points of sleep science, we hope your nighttime experience is peaceful and restorative.