“To facilitate sleep onset, you drop your core temperature and raise your peripheral temperature,” explains Professor Dawson. “And the hotter it gets, or the colder it gets, outside of what’s called the thermal neutral zone, the more difficult that is to do.”
For most people, the thermal neutral zone is considered to be between 18 to 28 degrees (in your bed, not outside).
“If you live in the tropics it tends to adjust up, if you live in a temperate climate it tends to adjust down,” Professor Dawson says.
If you are hotter than this, your body will not be able to lose sufficient heat to lower your core temperature.
Contrary to popular belief, it is unlikely that you are waking up on a hot night because you are dehydrated. Basically, says Professor Dawson, you’re waking up because your body is struggling to regulate its temperature.
Sydney resident Christopher Pearce, who lives in a terrace house with no airconditioning or ceiling fan, said he and his wife have developed tricks to beat the heat.
“We’ve been leaving the doors open, even the front door, I’ve been lying on the wooden floor boards until it’s cool enough at around midnight or a bit later,” Mr Pearce said.
“When the breeze comes through some times at night, with all the windows and doors open, it’s a bit better – but that’s something most people in the inner city wouldn’t normally do. I think it’s been pretty quiet, maybe when everyone’s back at work it might be a bit too busy to do that.”
Mr Pearce also recommends having a cool shower and not drying off completely before bed. But as for personal fans, forget about them.
“They don’t work. They just push the hot air around. The only thing I’ve ever had that works is a ceiling fan.”
So, how else can you bring your environment within the thermal neutral zone?
The “sweet spot” room temperature for sleeping is between 17 and 19 degrees, Professor Peter Eastwood, president of the Sleep Health Foundation, says.
“Make your room dark, keep the noise down and remove things that go ‘ping’ in the night like phones. It’s about making your bedroom as good a sleep environment as possible.”
Removing the doona and using sheets in breathable fabrics such as linen or cotton will help, Professor Eastwood says, along with seasonal pyjamas, or just “go starkers”.
“I’ve heard some strange things – people putting their sheets in the freezer and things like that,” he said.
Mary Ward is a Lifestyle reporter for The Age, The Sydney Morning Herald, Brisbane Times and WAtoday.
Matt Bungard is a journalist for the Sydney Morning Herald.