Have you ever woken up in the middle of the night kicking off the blankets and feeling like someone turned your bedroom into a sauna? You might remember feeling all warm and cozy when you were getting into bed, but somehow during the night the heat just became too much. No, it’s not your body trying to play a trick on you—it’s actually just trying to tell you that it sleeps best in a colder room. Let’s look at the “why” behind this unique sleep factor, and some tips for getting your bedtime feeling juuust right.
Why your body likes it cold at night
In his book Why We Sleep, renowned sleep scientist Matthew Walker explains the connection between an evening drop in temperature and your body drifting easily into sleep: there are a group of thermosensitive cells that sit in the center of your brain which are able to detect a drop in your body temperature of a couple degrees. When this drop is detected by the cells, they send a signal to the nearby suprachiasmatic nucleus (or SCN), which is pretty much the CEO of your sleep.
The message from these cells, along with the signal of fading daylight, gives the SCN the thumbs-up to let it know it can initiate the evening surge of melatonin. As Walker puts it, “[e]nvironmental light and temperature therefore synergistically, though independently, dictate nightly melatonin levels and the sculpt the ideal timing of sleep”.
Your sleep’s attachment to lower temps at night ultimately stems from an evolutionary connection we have to the twenty-four hour cycle of warmth and coolness. Our ancestors who slept under the open sky (or tents or other shelters not far removed from the natural environment) got so settled into the habit of heading to bed in the dark that we also got used to the cooler temperature that would result from the setting of the sun.
Fortunately for us, but rather unfortunately for our sleep, most of us now enjoy a little bit more sturdy, temperature-controlled shelters. With so much of our environment now under our control, it’s a good idea to look at how we can shape that environment to be nice and cool for our sleep no matter what.
How to beat the heat:
The ideal temperature for falling asleep and staying asleep is 65 degrees Fahrenheit. The exact number can be slightly different depending on age, gender, and weight, but 65 degrees is the temp that everyone should generally be aiming for. So...
...the best practice is to lower the temperature to between 65 and 68 degrees F in the evening. With the power of the thermostat comes great responsibility. When we neglect to lower the temp at night, our body’s core temperature is unable to drop, leaving us susceptible to a fitful sleep and nighttime wake-ups. If you’re unable to pick your temp precisely, you should try to make your room (or at least your body) feel cool, whether that requires opening up windows or turning on a fan.
A quick face wash or a hot bath make for great helpers. As we discussed above, our hands and face make useful tools for our bodies to dispense with our inner heat at night. Running water over your face and hands will help draw out the heat with even more efficiency. Similarly, a warm bath will invite blood to the surface of your skin (hence the flushed look of your skin after stepping out), helping to radiate out heat and lowering your body’s temperature.
Take a look at your sleeping layers. Are your pajamas light and breathable? The same question goes for your blankets, as well. Be mindful of the fabrics you choose for the bed—synthetic fabrics like polyester trap heat more than natural ones like cotton, wool or linen.
Don’t sweat your sleep
No one likes waking up in the middle of the night, covered in sweat, kicking furiously at once-friendly blankets now turned into suffocating monsters, discovering that the cool side of the pillow has ceased to be. When it comes to sleep, the best defense is always a good offense: make sure to plan ahead, and lower the temp before settling into a deep slumber.