Who doesn’t love freshly baked bread?
Bread, like sleep, is a time-ordered process that depends on having the right temperature at the right time. First, we need time to let the dough rise in a warm environment, allowing the yeast to do its work. Then, when it’s time to bake the loaf, we need the higher temperature of the oven for the chemical reactions to occur. Finally, when the bread is finished, a distinct cooling process lets the final structure set before it’s ready to eat.
Sleep is a temperature-dependent process, too. Learning how to regulate body temperature while sleeping starts with understanding this cycle.
Our body temperature fluctuates over 24 hours, peaking between 6 and 8 p.m. To fall asleep in the evening, a cooling process must occur. We reach our nadir, or low point, between 4 and 6 a.m., after which our body temperature rises to help us wake.
And like bread, when the process doesn’t go well, it results in crumby sleep. (Please laugh.)
How Temperature Affects Sleep: The Brain Connection
The preoptic area of the hypothalamus is the region of the brain that regulates both sleep and body temperature. It integrates these two processes because they’re interconnected. Body temperature is inextricably linked to sleep.
Understanding how temperature affects sleep requires understanding how we regulate our temperature in the first place.
Core Temperature vs. Peripheral Temperature
We have two locations of body temperature to consider:
- Core body temperature is what you’d measure with a thermometer under your mouth (or rectally, for infants)
- Peripheral body temperature is what a wearable like an Oura Ring measures at your fingertips or extremities
Our body uses different tools to regulate core body temperature. To raise core temperature, we can:
- Enhance metabolism (shivering, burning more calories)
- Reduce blood flow to the periphery through vasoconstriction
To lower core temperature, we can:
- Slow down metabolism
- Increase blood flow to the periphery through vasodilation
- Sweat
Blood doesn’t just carry oxygen and nutrients. It also carries heat energy. Our periphery has many blood vessels on its surface, which act like radiators. The more blood that flows to the periphery, the more heat energy is lost from the body.
When we vasoconstrict, those small arteries tighten, reducing blood flow to the surface and conserving heat in the core. When we vasodilate, we open those “radiators” and release heat, lowering core body temperature.
Why Hot Environments Disrupt Body Temperature While Sleeping
Most of us have experienced how sleep environment impacts sleep quality. If you’ve ever tried to sleep during a heat wave without air conditioning, you know it’s miserable.
Our body temperature peaks in the early evening. To fall asleep, we need to lower our core body temperature. That can’t happen if the external environment is too warm. Exogenous heat becomes the enemy of healthy body temperature while sleeping.
How to Regulate Body Temperature While Sleeping: Low-Tech Solutions
If external heat can hurt sleep, temperature modulation can enhance it. Some methods to regulate body temperature at night have been around for generations.
The Warm Bath Paradox
We’ve established that exogenous heat impairs sleep, yet taking a warm bath one to two hours before bed, for as little as 10 minutes, has been documented to improve sleep onset and quality.
When you’re in a hot bath, your body absorbs heat energy and responds by vasodilating to dissipate it. When you get out of the bath, you’re still vasodilated. You’ve opened those radiators.
You actually lose more body heat after the bath because of this vasodilation, which lowers your core body temperature and primes your body for sleep.
Warm Socks at Bedtime
The same principle applies to putting on warm socks before bed. This old wives’ tale has a physiological basis: warming your extremities causes vasodilation, which helps dissipate heat from your core.
It’s a simple way to regulate body temperature at night without any special equipment.
How to Regulate Body Temperature at Night: New Technology
On one hand, we have wool socks and warm baths. On the other, we have high-tech solutions like temperature-regulating mattresses.
The leading technology in this space is the Eight Sleep mattress cover, which uses water-filled coils and a pump to adjust the temperature from about 55 to 110 degrees Fahrenheit. The Eight Sleep also uses sensors to detect respiratory rate, heart rate, and temperature to infer what phase of the sleep cycle you’re in, allegedly adjusting temperature accordingly.
Does it work? Two questions are built into this:
- Is modifying external body temperature via a temperature-adjusted mattress effective?
- Can the device accurately identify your sleep phase to deliver the right temperature at the right time?
I dove into the literature, and both questions remain unanswered. The company hasn’t described its sensing technology or validated its accuracy.
One industry-sponsored study exists, but it had only 54 subjects with a mean age of 36. Younger people sleep more easily, making this an unchallenging test population. The methodology involved only eight nights (four with, four without), and while it showed some improvement, the overall study design was too weak to draw conclusions.
The device costs $3,000–4,000. It offers a 30-day money-back guarantee. Like many new technologies, it’s commercially available and holds high promise, but we lack solid evidence of its efficacy.
How Temperature Affects Sleep: Individual Variability
How temperature affects sleep varies across individuals, genders, pre- and post-menopause, and age groups. You need to be attuned to what works for you. My ideal 64 degrees might be your ideal 71 degrees.
For couples, this creates a common challenge. More often than not, partners can’t come to a consensus on sleep temperature.
Be prepared to defend your individual needs. Anyone who’s shared a bed knows this struggle.
Bedding and Sleepwear
What about pajamas and bed covers? The gurus speak as if natural fibers and breathability are gospel, but no scientific studies definitively prove this.
That said, based on first principles, it makes sense. Your body needs to modulate temperature throughout the night, sometimes releasing heat, sometimes conserving it. Natural fibers that breathe and don’t trap heat allow your body to self-regulate better than synthetics.
The evidence isn’t there, but the logic is sound. Choosing breathable fabrics is one more way to regulate body temperature while sleeping.
How to Regulate Body Temperature While Sleeping: Today’s Takeaways
Understanding how to regulate body temperature while sleeping comes down to a few key principles:
- The temperature of your environment is intimately linked to your ability to sleep. This isn’t theory. It’s biology, controlled by the same part of your brain.
- Tried-and-true low-tech solutions work. A warm bath one to two hours before bed, warm socks, and a thermostat set to your personal comfort level are all validated approaches for managing body temperature while sleeping.
- Respect individual variability. Don’t chase a specific number. Experiment to find what works for you, and in shared sleeping arrangements, advocate for your needs.
- New technology shows promise but lacks proof. Products like the Eight Sleep mattress are commercially available, but the science hasn’t caught up to the marketing.
At Banner Peak Health, we’re fascinated by sleep and watching this space closely. Stay tuned for further developments.
