What are you wearing?
No seriously, what are you wearing to bed? Because it can affect the quality of your sleep.
"What you sleep in can alter the temperature, [that] is the main thing in terms of how it may affect your sleep," explains Kathleen Maddison from the Centre for Sleep Science at The University of Western Australia.
"Temperature change is super important in helping us fall asleep and then helping us stay asleep."
What we wear to bed also comes down to comfort — and even safety.
"If you're at home alone and you're a sleepwalker … you might select pyjamas in case you go wandering," says Dr Maddison.
So as we head into summer, what is the best thing to wear — or not to wear — to bed?
What you said you're wearing in bed
We asked our Instagram audience and 16 per cent prefer to sleep "nudie rudie", 60 per cent in pyjamas, 16 per cent in just their undies and 8 per cent in "something else".
"Ghosts" were one of the reasons for wearing pyjamas. Another person told us: "I fell out of bed and broke my arm real badly. I was naked at the time."
For those against wearing anything in bed, getting tangled up in clothing as they move around during the night was a top justification.
While there isn't peer-reviewed research focused on bedwear, Dr Maddison says mattress and bedding companies have conducted surveys over the years.
Their findings are generally pretty close to what our Instagram followers voted.
Dr Maddison says it's really climate dependent — where people live, and what season it is — but the survey data doesn't capture these details.
"These are companies just putting surveys out, which is a nice starting point, but they haven't asked for geo locations. They haven't specified time of year."
Temperature and sleep in the heat
Feeling too hot or cold can affect our ability to fall asleep and stay asleep, says Dr Maddison.
It's important to get it right, because sleep impacts almost every part of the human system, and getting a good night's rest may even be a factor in how long you live.
What you wear, the ambient temperature of the room, and the type of fibre your mattress and bed linen are made of will all have an effect on your sleep.
If it's hot and you lie naked on top of your bed sheets with the fan on, that will keep you cooler, says Dr Maddison.
"If you sweat and then you have air flow over your skin, that is a cooling mechanism."
That might sound obvious, but there is evidence pyjamas can help with temperature regulation in certain conditions.
Sleeping naked can make you feel even hotter because it may not allow moisture to evaporate between your body and your mattress.
That's why other factors like what bedding you have, and whether you use an air conditioner or fan, come into play. You may need to trial what works best for you.
Leon Lack is an emeritus professor at Flinders University with a special interest in sleep.
He says the ideal room temperature varies between 15 degrees Celsius and 22C.
"If the ambient temp is 24C, you could get away with just sleeping on top of the mattress without any covering.
"But the main thing is to experiment. For some people that will be too chilly, and they would need at least a sheet to feel comfortable."
For couples who share a bed but feel hotter or colder than one another, he recommends investing in two different bed coverings.
Health and hygiene factors
If you're sleeping in the nude, you will likely need to wash your bedsheets more often, says Dr Maddison.
"We do lose dead, flaky skin. There are bacteria, and if you don't have that extra layer of pyjamas between you and your bed linen, you may need to increase the frequency [of sheet washing]."
If you are wearing underwear to bed, she says there is evidence to show making sure it's not too tight and a breathable fabric is important.
Wearing tight synthetic clothing and underwear can make the vulval environment hot, and can cause vulval irritation, for example.
And some research has suggested that wearing tight underwear may decrease sperm counts, although other studies have not found this to be the case.
