Couples who share a bed may know all too well the pain of being woken up by their other half feeling far too hot or cold.
But scientists may have found a way to end the arguments caused by sleepless nights – and the secret they say is all in the duvet.
Research has found that a wool-filled duvet helps regulate sleepers' temperature more efficiently than feather, down or polyester fibre-based bedcovers.
Overheating during the night is usually caused by the build-up of moisture created by sweating in sleep, which traps heat and causes a vicious cycle of further sweating and heat build-up.
One survey found a third of Britons complain about being too hot at night and are most likely to wake during the crucial regenerative stage for sleep between 2am and 5am.
But University of Leeds research, published today, showed using a wool duvet could help solve the problem.
Wool fibres are based on the protein keratin – which is also found in our hair, nails and skin – and have a natural ability to hold up to a third of their own weight in moisture before feeling damp. They naturally draw heat and moisture away from the body, helping to maintain a comfortable temperature.
People produce heat and perspire at different rates, but wool can control the microclimate around each body allowing people to remain comfortable under the same duvet.
It means even when a couple shares a bed, heat will be drawn away from a person who tends to overheat at night but not from their partner who stays cool, leaving both sleeping soundly.
The study compared wadding from different types of duvet on sale in the UK to examine their thermal insulation properties and moisture management – factors essential to keeping cool and preventing disturbed sleep.
Researchers analysed how the duvets cooled down from an extreme temperature of 70C (158F) and how they performed in the ideal environment for sleep of 17C (63F) and 45 per cent relative humidity.
The waddings were tested using Sweating Guarded Hot Plate technology which mimics how the human body changes during the night.
In tests, wool allowed 67 per cent more moisture to escape over an eight-hour period than a feather/down wadding, and 43 per cent more than polyester.
Wool was able to cope with nearly double the amount of perspiration per hour than feather/down and around 50 per cent more than polyester.
In terms of heat management, wool was able to maintain the optimum body temperature for sleep of 35.1C (95F) for the longest, while feather/down and polyester were unable to maintain the temperature and instead caused it to exceed 36.1C (97F).
Dr Ningtao Mao, of the University of Leeds, said: 'It is clear that the greater water vapour resistance is not due to the greater thickness of both polyester hollow fibre and feather down duvets, but due to the both the fibre properties and their wadding structures.'
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