It is perhaps unsurprising that a study commissioned and funded by the wool industry would conclude that wool is the best material to sleep in, but we’re not cynical here. The study, by the University of Sydney, has found that wearing wool pyjamas over cotton can result in up to 15 minutes extra sleep. Wool, apparently, regulates body temperature better and keeps our bodies in the “thermal comfort zone” conducive to better-quality sleep.

Wool has also been called a “super-fibre” thanks to its moisture-wicking properties (especially useful for those who suffer night sweats), which is the sell behind wool duvets. The National Sleep Foundation, a US nonprofit, lists wool among its recommended materials to sleep in (but notes itchiness as a possible issue). It also promotes silk, which it calls a “thermoregulator”, but warns it might be “slippery” as well as expensive. There is no mention of sleeping nude, but flannel and, weirdly, bamboo are other options.

According to a survey last autumn, 40% of adults in the UK wear pyjamas in bed, 20% wear underwear and a third wear nothing. But guess what? That survey was also commissioned by the wool industry to push its products. So, basically, the wool industry wants us to just follow everything they say, like sheep.

It is well known that worrying has a negative impact on our ability to sleep, so perhaps not stressing too much about pyjama material is the best advice. Then again, perhaps there is something else to worry about – skincare experts are trying to persuade us that cotton pillowcases cause wrinkles because of friction.

The NHS doesn’t seem too fussed about pyjama material, however. Its sleep hygiene guidance includes a room temperature of between 18C and 24C, thick curtains to increase darkness and keeping tech in other parts of the house. So wear what you want – advice that also applies when you’re awake.