Too hot to sleep? How to wake refreshed from a sweaty El Niño night

As the temperatures climb, sleep scientist Leigh Signal shares her tips for cooling down and getting a good night's rest this summer.

It’s 2am and you’re tossing, turning, sweating, kicking off the duvet and then tossing some more. It’s horrible, and only going to become worse as hot, dry El Niño intensifies.

Many people struggle to sleep through the warmest weeks of any summer, and this year, with El Niño already delivering atypical heat (not to mention summers getting progressively warmer all over the planet) some Kiwis will be experiencing restless nights.

Massey University sleep scientist Leigh Signal says the optimal bedroom temperature is between 17C and 19C, which is difficult to achieve during a summer like this one, with already high temperatures predicted to peak at the end of this month.

You don’t need to be a scientist to understand the importance of sleep for daily functioning, but why do some seem to suffer through these warm nights than others? Perhaps you’ve been wondering if there’s a secret sleep recipe you haven’t seen? Some code you haven’t cracked?

Signal has over 20 years' worth of sleep wisdom to impart. She emphasises there is no “perfect” routine for good sleep, but there are some simple things one can do to form everyday patterns that can help.

To get to the core of the issue, we need to talk about core temperature.

Signal describes the circadian body clock as an internal timekeeping system that programs us to sleep at night and be awake during the day.

“The fact that my tummy is ready for breakfast when I wake up in the morning is because my clock has kicked in,” she says. “It provides input into a huge range of processes.”

Circadian rhythm also controls core body temperature, which increases throughout the day and then starts to ease off as we’re heading to bed. It’s so natural you probably don’t even notice it happening.

"Our skin temperature increases slightly during sleep, but research suggests we sleep better in environments that are cooler, so we need to have optimal conditions to allow those two things to happen reasonably easily… If we're too hot, that's when we’re going to have poor quality sleep.”

If our bedroom is too hot, we may wake more regularly and our sleep might not be as efficient or high quality as it would be in a slightly cooler environment. But how do you maintain that optimal 17C and 19C when it can be as warm as that outside?

“Think about trying to keep your bedroom cool throughout the day," says Signal. "Try shutting the blinds so that the room doesn't heat up as much and then it is easier to cool down at night.

“Also try to create an airflow across the body, so having one window open is good but it might be best to think about opening a window on either side of the room to create a flow through,” she says.

Airflow can also be created using a fan, as most New Zealand homes don’t have air conditioning in the bedroom.

“For some people a fan is a great idea as they actually like the noise, but for other people they hate the noise of a fan… so maybe a fan with or without ear plugs,” she suggests.

When it comes to bedding, Signal’s advice is to ditch the synthetics and rock some high-quality fabrics like cotton and linen, as these allow our skin to cool down better.

“That goes for both your bedding and also your PJs or what you wear to bed at night,” she says.

And don't tuck yourself in tight. Being able to get your extremities – that is your hands and feet – out of the bed is important, says Signal. As is having layers of bedding to provide options, like a cotton sheet as well as something to pull over the top of you for when it does cool down at 3am.

“My partner likes three layers but I get way too hot, so I might only need two… you may want to think about different numbers of bedding layers on either side of the bed,” she says.

Another idea is to have a cold shower before hopping into bed, or using a cool washcloth to bring down the body’s core temperature.

Your approach and attitude towards sleep makes a big difference at the best of times (which 3am in an El Niño summer isn't).

If you’re stressed, thinking about all the important things you have to do tomorrow and how you’re not getting enough sleep to be your best, you’ll work yourself into a state that makes the cycle worse.

Signal’s advice: “try not to get frustrated if you’re having difficulty falling asleep or you've woken up in the middle of the night and you're feeling hot and uncomfortable.

“If you have been lying there for a while and you're really struggling with falling asleep or staying asleep, after about 30 minutes we recommend getting out of bed. Do something quiet or relaxing until you feel sleepy again and then go back to bed.

“Because what we don't want to do is create an environment, your bed and bedroom to be associated with being frustrated and annoyed and having difficulty falling asleep,” says Signal.

Signal said quiet activities include reading a book in dim light or listening to a podcast, but NOT SCROLLING ON SOCIAL MEDIA. I repeat, NO SCROLLING.

Signal stresses the importance of sleep as a “fundamental pillar of health”. But we don't have to strive for absolute perfection in our approach to it.

“It's like diet and exercise… we don't have to be perfect every day to be generally healthy and well, but we want to get it right most of the time,” she says.

That said, she's passionate about fatigue management, citing many waking functions that poor quality sleep could impact.

She names a few: “It's important for our emotional health and wellbeing, for our cognitive process, being able to pay attention, concentrate and be situationally aware.

“It's also really important for our ability to respond quickly to events and circumstances that are happening around us."

Poor quality sleep can also play a part in derailing health and fitness goals by impacting metabolic processes.

“We feel hungrier, and we don't feel as full when we do eat, so there's this huge relationship between sleep and the appetite,” Signal says.

Signal's advice to those who've slept badly is to take extra care the next day, especially while driving, as our brain will find it more difficult to solve problems and engage complex reasoning.

And try to be empathetic when dealing with family members who are struggling to sleep. “We all know, anecdotally, if you've had a bad night's sleep or someone that you live with had a bad night's sleep, the next day they are grumpier, they might be more withdrawn and they might be more up and down… one minute they feel okay, the next they snap at somebody,” she says.

She crosses her fingers as she speaks about this summer.

“We might have a few nights where it's really hot and nobody is sleeping particularly well, and then hopefully… the temp drops off and then we can all have a good night's sleep,” she says.

“Unless you’re my husband, in which case you’ll sleep through anything."