Sleep is an important part of restoring the body, but sometimes external factors can interfere with our ability to get to sleep and with our quality of sleep. Trying, but failing, to sleep in the heat or feeling overheated due to an airless or stuffy room can be exhausting, so let's find out how heat can impact your sleep and what you can do to stop it.
How heat affects sleep
Our circadian rhythm maintains our sleep cycle, 24-hour cycles, which regulate essential biological functions. The body's Various processes follow its circadian rhythm, such as digestion, hormone secretion, and, most importantly, the sleep-wake cycle.
The body's central timekeeper, the hypothalamic suprachiasmatic nucleus (SCN), receives cues from light, temperature, and other environmental elements, which is why temperature is a critical factor in falling asleep and staying asleep.
Suppose these ecological factors are operating in harmony with the circadian rhythm. Sleep quality increases. In contrast, if something is out of sync, this can disrupt your sleep — and lack of sleep can lead to a host of physical and mental misalignments.
Thermoregulation and sleep
Decreases in our core body temperature (CBT) allow us to sleep. The higher your core body temperature is, the less likely you'll have a night of restorative sleep. An adult CBT is around 37⁰C (98.6⁰ Fahrenheit) and oscillates by a couple of degrees during the night (slightly different in children and babies).
In the evening, when your eyes perceive darkness, they send a message to your SCN, which secretes the sleep hormone melatonin, allowing your body temperature to decrease and slowly prepare your body for sleep.
Falling asleep may feel effortless, but behind the scenes, your body completes various processes to help you cool down and slip off into dreamland. To cool down, your body must direct heat away from its core.
Enter your circadian clock, the SCN, which encourages the blood vessels in your skin to swell slightly, allowing more blood to flow to the limbs for heat to escape.
This process is known as vasodilation and causes momentary warmth in the hands and feet. Once your core body temperature drops, it remains low throughout the night, rising again just before you wake up.
If your body temperature is up against room temperature due to hot weather or a stuffy room, your body will struggle to reach this temperature. As a result, you'll find it difficult to fall asleep and have a poorer night's sleep.
Bedroom temperature vs body temperature
According to a bedroom poll by the (US) National Sleep Foundation, 79% of respondents voted that having a cool bedroom was one of the most essential features of a restful night's sleep. The foundation says the optimal bedroom temperature for sleep is around 65⁰F (18.3⁰ C) — but this can differ between individuals.
The foundation also recommends keeping your thermostat between 60 and 67 (15.5 and 19.4⁰ C) for a good night's sleep. If you feel the heat more than others and it's impacting your ability to fall asleep, turning the thermostat down entirely at night may help with temperature regulation and signal your body that it's time for bed.
It's not always easy to cool down a room or measure its temperature despite using room temperature controls, like air-con or central heating. The circadian rhythm is very responsive to features such as light, diet, and exercise, so we can focus on adjusting our lifestyle and sleeping environment to help regulate our body's natural core temperature.
How to Sleep in the Heat
Now you understand how the heat might disrupt your sleep, and you can start making a few changes. The strategies below will help you keep your natural internal temperature controls happy and stop the heat from interfering with your sleep.
Keep your bedroom dark.
Blocking out the sunlight by closing your curtains or blinds throughout the day will keep your room cooler. Blackout blinds are best for ensuring the sun's heat won't creep its way in and radiate through your windows. Light levels are one of the main factors in circadian rhythm regulation, if not the main one. A dark room will not only keep you cool but will also ensure you improve your quality of sleep, mood, and general wellness.
Turn off electronics
Electronic devices cause energy to flow into the air, so removing electronics from your bedroom that emit light and heat will also help. Of course, if you're getting ready for bed or reading in bed, you can't have complete darkness, so in this case, you should stay away from blue light emitted from electronics or LED lights. Use dim or red lights, which will encourage sleep, instead.
Maintain a bedtime routine.
Hot weather can often cause you to change your bedtime routine. The extra hours of light in summer make it tempting to stay up later and enjoy the summer evenings. You tend to stay outside longer, eat later, and go to bed later — but this isn't good for your circadian rhythm. Going to bed simultaneously each night will encourage your body to naturally prepare for sleep in line with its usual cycle.
Use a light summer duvet.
You're missing a trick if you keep the same duvet on your bed all year round. Swapping out your heavy winter duvet for a light, airy summer duvet is one of the first things you should do if you're struggling to sleep due to the heat. You can also opt for a dual-season duvet connected in the winter and pull apart in the summer.
Try natural bedding
Try sheets, duvet covers, and pillowcases made from cotton, silk, linen, or other breathable materials to avoid sweating during the night's heat. Synthetic materials such as polyester do the opposite — they make you sweat, so before you buy a new set of bed linen or decide what bedspread to use during warmer temperatures, it's a good idea to check the label for the list of fabric fibres.
Find the right mattress and pillow.
It might be worth investing in a different mattress and pillow if you're prone to night sweats and overheats in bed, regardless of high temperatures.
Mattresses from dense foam absorb heat, whereas cooling beds with hydrophilic fibres and vents will regulate your body temperature and help you keep cool during the night. Cooling pillows are also necessary if you have difficulty sleeping in the heat.
moisture or cold, keeping the body temperature at an optimum 37 degrees.
Cooldown, your bed
If you're not ready to invest in a cooling mattress or pillow, using a traditional silicon hot water bottle to make a cold compress is a simple, effective way to stay cool at night-time.
Here's how you can quickly make an iced water bottle
- Fill your water bottle with cold water and ice.
- Make sure the bung is tightly closed.
- Wrap the water bottle with a towel.
- Since the body emits heat from its extremities, place the cold water bottle in your bed by your feet or hands.
Then you're ready for a comfortable and chilled sleep on a hot night!
If you want to go one step further, The (US) Sleep Foundation and The Sleep Council UK advise putting your pillowcase(s) or socks in the fridge or freezer just before bedtime — if you're opting for the freezer, be sure to put them in a reusable plastic bag first. This tip may surprise you, but it's an easy way to help lower your core body temperature.
Wear pyjamas
Yes, this seems illogical when you're restlessly tossing and turning in bed because of the heat. Logic says wearing nothing but your birthday suit will cool you down, but no. Contrary to popular belief, wear pyjamas if you're feeling hot at night.
Why?
Well, according to sleep expert Sophie Bostock your PJs are like a "moisture-wicking surface" that wipes away any sweat droplets that build upon the skin's surface and keeps you cool — whereas if you sleep in the nude, this layer builds up and has nowhere to go. Like the material of your bedsheets, it's worth checking out the fabric of your PJs — remember. Cotton is your friend, and polyester makes you hot.