How hot or cold a room is affects sleep. Researchers say a room between 20-25º Celsius is best. The researchers monitored 50 people aged 65 and older for 18 months. The people's sleep worsened when their room was not between 20-25ºC. Researchers say 20ºC is the best temperature fir a deep sleep.

Sleep quality could fall by 10 per cent if it is too warm or too cool. Poor sleep can bring health problems, like diabetes and heart disease. It can also increase stress. The researchers said people should make a comfortable environment to sleep well. They also said climate change could change our sleep.