"You're too hot" might not be a complaint you'd expect to hear too often in the bedroom, but with bedroom temperature being one of the biggest sleep disruptors, running at a different degree to your bed partner can be a serious sleep sucker.
Professor Drew Dawson, CQ University sleep researcher, says there are a few factors that cause some people to wrap themselves in a dressing gown and double doona while others sweat beside them.
For starters, men tend to run hotter than women as a result of having more muscle mass, which generates more heat than fat.
"Body temperature is a reflection of metabolic rate — if somebody pushes a lot of weights they will push their basal metabolic rate up and run hot," Professor Dawson told 9Honey Coach.
Hormones can also play a part, with women's body temperature varying across the month.
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"Changes in hormone levels in women across the menstrual cycle and at menopause also produce marked changes in [temperature regulation]," Professor Dawson explains.
"A lot of fertile women's partners will say, 'You're so hot you're virtually glowing in the dark' at certain times of the month and many women in menopause and peri-menopause will pull blankets on and off and disrupt their partners enormously."
Your body temperature will also vary throughout the night as you drift between different sleep states.
"Body temperature decreases during the night-time sleep phase and rises during the wake phase," Rob Grunstein, professor of sleep medicine at the University of Sydney, writes on The Conversation.
"Sleep is most likely to occur when core temperature decreases, and much less likely to occur during the rises."
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A modern complaint
Professor Dawson says complaints about hot bedfellows is a relatively new phenomenon.
"A man and woman sleeping together in the same bed is a relatively new phenomena in human history. For thousands of years in indigenous communities men and women didn't sleep together like out of post-Victorian England," he points out.
"Up until 150 years ago, nobody could afford to have one or two people sleeping alone in a room. The bed was the biggest purchase most families made after their house. It was very common for families to sleep with three or four people in a bed, top to toe.
"The idea of a couple in a bed in a room on their own as the setting for sexual behaviour is a relatively new phenomena."
Perhaps we need to take a leaf out of Scandinavian countries where Professor Dawson says people tend to sleep with two single beds pushed together.
"Each person has their own mattress, usually with a foam layer across the top and their own doona of different thicknesses to allow for different thermoregulatory dials," he explains.
"[Couples in Australia] usually have to compromise between what suits both of them, which usually means it suits neither."
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How to cope with a huge temperature variation
If your partner sleeps at a completely different temperature to you, Professor Dawson suggests using different bedding.
"With two people under the doona, they are both heating the air and if your partner heats the air more than you like it can cause a problem," he says.
"Use two doonas — a hot one and a cold one — that way the microclimate around one person's body doesn't influence the microclimate under the other doona."
If you're squashed into a double bed, it might also be worth considering a king size that will enable you to move far enough apart to keep your temperature to yourself.
"Latex beds that don't breathe very well make people very hot," sleep scientist Dr Carmel Harrington told ninemsn Coach.
"Always make sure the layer closest to you is breathable and your sheets are made from natural fibres so they can wick away the temperature and sweat."
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