Which bed sheets are coolest on hot summer nights? Polyester, linen or cotton?
Tossing and turning all night? A fan, cool shower, and even your bed sheets may help you nod off faster. (Getty Images: Peter Dazeley)
There's nothing like tossing and turning on a hot night, drenched in your own sweat, to fully experience an Australian summer.
For those of us without air conditioning at home (let alone in our bedroom), trying to sleep through sweltering temperatures can be frustrating and uncomfortable.
A big reason for hot, sleepless nights is our body's need to drop its internal temperature slightly to nod off.
The typical ideal room temperature for falling asleep is around 18 degrees Celsius. But if the room is warm and we can't cool off easily, we find it harder to fall asleep and stay in deep sleep.
Sleeping with a fan on or the window open can help. But can switching our bedsheets make a difference too?
We asked the experts about the cooling qualities of the main types of sheet fabric available, from natural fibres to synthetic textiles.
Let's start with the most popular bed sheet fabric in Australia: cotton.
Cotton sheets
Natural fibres such as cotton are known for their breathability and their capacity to absorb more moisture than synthetic materials, which is ideal on sweaty nights.
"It's the act of moisture being pulled away from your skin that makes you feel cool," Rebecca Van Amber, from RMIT University's school of fashion and textiles, explains.
Dr Van Amber says whatever the material, a thicker fabric will feel hotter than a thinner one. (Supplied)
However, Dr Van Amber says not all cotton sheets are created equal.
While she says thread counts are "a little bit of a made-up number" used for marketing purposes, they could point to a thinner, cooler fabric.
"A higher thread count generally will mean a finer yarn, and a finer yarn will generally mean a thinner fabric."
There's also differences between weave types, with sateen weaves creating a silky feel, percale often producing breathable fabrics, and flannels ideal for cosy warmth.
Linen sheets
Linen is another natural fibre. It's also known for its breathability and moisture absorption.
Chin Moi Chow, a sleep researcher at the University of Sydney, says linen sheets can help reduce "thermal stress" — the discomfort we experience when we're too warm or too cold.
"Linen has a wicking action," she explains.
"It removes moisture from your skin through [its] fibres, and then to the external environment," away from your body.
Dr Chow says both linen and cotton are great at absorbing sweat off the skin.
Dr Chow says one Japanese study found linen sheets helped people nap better in hot conditions.
Study participants sleeping in cotton sheets woke more often and didn't sleep as deeply as their linen-wrapped counterparts.
Dr Van Amber says the linen vs cotton debate comes down to your own personal preference, as well as the sheets themselves, which will differ between brands.
Some linen sheets can end up being a thicker fabric than cotton, so could feel warmer.
However, they're often made in an "open weave", where the fibres are spaced further apart, allowing more air flow.
Aside from aesthetics, what should you look for when choosing bed sheets for summer? (Getty Images: FreshSplash)
Dr Van Amber says linen will feel coolest when air's blowing through the fabric, so suggests sleeping with a fan pointed at you in hot weather.
Bamboo sheets
Dr Van Amber says natural bamboo sheets are "not a thing" in Australia.
"If it's marketed as bamboo, it's viscose, it's rayon, it's what we call a semi-synthetic fibre.
"It's bamboo that's been put through an extremely heavy toxic chemical process to create this [material] that is basically a reconstituted fibre."
She says this process creates a long fibre with properties "kind of halfway between polyester and cotton", creating a silky, fine sheet.
While thinner sheets can be cooler than thicker ones, Dr Van Amber says semi-synthetic bamboo is unlikely to absorb as much sweat and moisture as 100 per cent natural fibres, and could be more prone to pilling.
Polyester and other synthetic blends
Synthetic fibres such as polyester are not naturally breathable and are less effective at absorbing moisture than natural fibres.
Dr Van Amber says this can leave you feeling sweaty and clammy.
However, she says synthetic fibres are made from long yarns known as filament yarns.
These microfibres are great at creating thin, lightweight bed sheets that don't get as wrinkly as materials like cotton.
"They do have quite a silky sort of feel, and some people might prefer that … it really comes down to personal preference," Dr Van Amber says.
Other bedding tips for hot weather
Dr Van Amber says it's not just sheets that affect how hot you feel at night.
"It's everything that's on the bed. It could be the mattress, the mattress topper, your doona or duvet; everything. It's really a whole system of bedding."
While it may sound counterintuitive, Dr Van Amber says wool can also be a great option in summer.
"Some people might find that [using] a wool mattress topper might actually make them feel cooler, because wool has a great buffering effect."
It is also known for its ability to absorb and wick away moisture and sweat.
Sleep Health Foundation CEO Moira Junge adds that the surface of your hands and feet are essential when it comes to letting go of heat.
She says sticking your feet out from under your sheets, or even covering your hands and feet with damp cloths, could help with sleep on those particularly hot nights.