Naked. Topless. Just socks. Eskimo-style layers. Bathrobe. Whether you're used to sub-zero temperatures or 40C climates throughout the year, you'll no doubt have adopted your own unique way of dressing for bed time.
However, new research, reported in the journal Nature and Science of Sleep, has found that wearing wool pyjamas to bed, instead of cotton, gives you up to 15 minutes extra sleep.
Why? Because wool is widely believed to keep the body in the 'thermal comfort zone' most conducive to restful sleep.
The study - carried out over periods of nine and four nights - involved scientists in Australia carrying out two studies of 17 students and 36 older sleepers to test the theory.
Students in their 20s in the first group feel asleep four minutes faster on average when wearing pyjamas made from merino wool rather than cotton, taking 11 minutes instead of 15. They also had an extra seven minutes more sleep per night.
Meanwhile the second study found that woollen pyjamas had an even bigger impact on older adults aged 65 to 70. The older generation fell asleep after just 12 minutes compared with 22 and 27 minutes for those wearing polyester or cotton pjs.
Both groups of volunteers were put to sleep in British-level night-time temperatures of 17C. Experts recommend a room temperature of just over 18C (65F).
Researcher Dr Paul Swan, from the University of Sydney, said: 'Not so long ago sleeping under wool bedding was the norm, and science is now rediscovering the benefits of sleeping in wool.
'Maybe it is not a coincidence because wool regulates your body temperature far better, keeping you in what is known as 'the thermal comfort zone'. You therefore not only fall asleep quicker, sleep longer, but also have deeper, better quality sleep.
'Enjoying good sleep has become increasingly difficult in modern times, and so anything that helps is great for your mental and physical health.'
Statistics from the British National Psychiatric Morbidity Survey show that as many as four in ten people in England suffer from some form of sleep disruption or insomnia.