November 26, 2020 6 min read
The body needs to drop 1–2 degrees Fahrenheit (around 0.5 to 1 degrees Celsius) in core body temperature in order to enter the sleep state. Decades of sleep studies and research have shown that the ideal room temperature range for initiating sleep is around 60 to 67 degrees F, or 15.5 to 19.5 C.
An optimal sleep temperature range allows us to fall asleep easier and have better sleep, but being in an active state of cooling accelerates and improves the entire process.
In order to understand the reason for these sleep temperature ranges, and how to take advantage of temperature regulation for restorative sleep, your health and wellness, we must first look at the physiological rhythms and changes that our body follows on a daily basis...
Coined from the Latin words Circa ("around"), and Diem ("day"), we use the term circadian rhythm to describe the naturally occurring 24-hour biological cycles.
Apart from the obvious sleep-wake cycle that guides our sleeping patterns, there are other important and coinciding cycles that most people are not aware of.
One of these circadian cycles is the body-temperature cycle. Your body automatically coordinates a slow and consistent drop in body temperature as you approach typical bedtime, reaching the lowest temperatures around two hours after sleep onset.
You might be surprised to hear that this pattern of temperature rises and drops does not depend on whether you're actually asleep or not.
If you were to stay awake in a brightly lit room, or left to rest in a completely dark room for 30 hours, your body's core temperature would still faithfully follow the below pattern.
As you might expect, these circadian rhythms are adaptive towards daylight hours and complement the rising and setting of the sun.
There are other important cycles that control, for instance, the secretion of melatonin, human growth hormone, and cortisol into the bloodstream. While all these cycles are endogenous, meaning they originate and are controlled from within, they still need to be adjusted by external cues in order not to veer off course.
The most important cue is light, particularly blue light, as it directly inhibits the production of melatonin – the hormone that controls our sleep-wake cycle.
Another important cue is temperature. Sleeping in a too-warm environment prevents you from dropping your core body temperature to the necessary amount for sleep to initiate.
Sleep environments that are too chilly can also impede sleep, however, it is much easier to fall and stay asleep in an environment that is too cold than one that is too hot.
Generally, it is better to sleep in an environment slightly too cool rather than too warm. A cooler sleeping environment actually helps initiate sleep, and has no obvious negative effects on the sleep-wake cycle.
Sleeping in the cooler ranges is also ideal for the production of melatonin, which apart from controlling our sleep-wake cycle also has anti-ageing properties on the skin.
Of course, there can be too much of a good thing; temperatures that are too frigid will just be uncomfortable and prevent you from falling asleep, so we recommend staying where you feel most comfortable in the ideal ranges of 60 to 67 degrees Fahrenheit, or 15.5 to 19.5 Celsius.
Sleeping in an environment that's too toasty will have noticeable detriments to the quality of your sleep. When overheating, we tumble and turn in our beds as our brain attempts to find positions and expose different parts of the body to cool down.
This restlessness can disrupt your progression through the sleep stages, which in turn leads to severe health consequences, especially over a long period of time.
You probably know that when we sleep we go through roughly 90-minute cycles that repeat until we wake up. An adult needs about 4 or 5 of these cycles to get the refreshing health benefits of sleep.
Each cycle is split up into three stages and a REM stage (Rapid Eye Movement). REM sleep is, among many other things, the stage where our most vivid dreams occur, and the most restorative benefits of sleep are gained.
Upon falling asleep, we spend very little time in REM during the first sleep cycles, but as the night progresses, increasingly more time is spent in REM.
Disrupting sleep during this finely tuned process can make you spend significantly less time sleeping in the REM stage. This can have grave consequences in memory, learning, emotional control, and physiological recovery.
You might be surprised to hear that 1.2 million car accidents are attributed to drowsy driving in the US – that's more than accidents due to drugs and alcohol combined.
In one study, participants were given alcohol until they were legally drunk and compared to people who were sleep-deprived for a single night.
In a concentration test, a perfectly healthy person with sleep deprivation (hasn't slept for 19 hours) is as cognitively impaired as someone who is legally drunk.
This is the grim truth of how consequential and important healthy sleep really is.
There is no one-size-fits-all approach to creating the ideal temperature for a good night’s sleep. Everyone's bodies, preferences, and environmental conditions are different and could be influenced in various ways.
Here are some approaches you can take to get into the optimal temperature range for sleep...
Comfy, heavy blankets and extra comforters are nice in the winter months, but can trap too much heat during warmer periods in the year.
Simple changes like having a lighter blanket, or even just using the blanket without the comforter inside it could be enough to make a difference.
Alternatively, you could also look into different materials, e.g. using a light, soft, breathable, cotton blanket during the warmer parts of the year.
Apart from changing the breathability of your blankets, you can also adjust the ambient temperature of your room. An obvious way to do this is to control the thermostat and air conditioning, but that is of course not an option for everyone.
Even if you have a thermostat, without proper home insulation or in large spaces it can be excessively expensive to maintain cool room temperatures.
A bedside fan can provide some meagre cooling, but also introduce noise and sensations that can impede or disrupt sleep.
Small adjustments, such as closing your curtains or blinds to block sunlight, or opening/closing the windows to improve or reduce heat exchange through airflow can also add up towards making a difference.
Yet another trick you can employ to keep the heat at bay is to introduce cool materials into the bed, or cool parts of your bedding itself. Though short-lasting, this might provide just enough cooling and comfort to get you to at least fall asleep.
One way to do this, though very inconvenient, is to slightly refrigerate the pillow before sleep, though keep in mind the effect will be very brief.
A more convenient approach is to use a hot water bottle. Fill one up with ice water and take it to bed with you. The ideal place for this is somewhere at the base of the bed, where the soles of your feet can make contact with the bottle.
The soles of the feet only second to the neck in terms of heat exchange. Though not providing cooling for long, the water bottle might provide just enough relief for you to fall asleep.
The most efficient way to reach an appropriate and comfortable body temperature is to cool or warm the body directly. Problems when sleeping are overwhelmingly caused by excessive heat rather than cold, and the sleep product market reflects this.
The neck is a particularly good point of attack when trying to cool the body down; a substantial amount of blood is circulating close to the surface of the skin here and can transfer a large amount of heat. Cooling this area is not only more effective, but far more energy-efficient than, say, keeping your entire room cool via a thermostat.
This is why there is a large market for cooling pillows that attempt to take advantage of this. There are various products out there that can help you maintain cooler temperatures during sleep onset and throughout the night, but have varying approaches and effectiveness.
For instance, there are buckwheat, or fiber pillows that dramatically improve airflow and therefore the pillow's heat dissipation. There are also special gel and foam or water pillows that are made of special materials that take much longer to heat up.
However, these are passive cooling solutions, and only increase the amount of time the pillow takes to heat up. This is why such solutions, while effective in some cases, simply don't work for everyone.
For this reason, we developed Moona. It's a smart device that uses active cooling to directly control body temperature to everyone's individual needs.
It selects and maintains an optimal temperature for each stage of the night by analyzing and understanding your best sleep patterns. Our algorithms learn from your sleep history to improve your REM, light and deep sleep after each night.