Hot or cold bath before bedtime?

By Lise Birk Kristensen

It has long been debated whether a hot or cold bath has the most beneficial effect on our sleep. Many people believe that a cold bath before bedtime has the best effect on sleep, but research suggests the opposite.

The body needs less energy at night than during the day as the body's energy production decreases. Therefore, when we sleep, our body temperature drops slightly (typically 1-2 degrees). This reduction in body temperature signals to your brain that it is time to get ready for bed and helps kick-start melatonin production, a hormone responsible for regulating your sleep.

Therefore, on a hot night, it is important to help maintain a good sleeping temperature. It can be tempting to take a cold bath before bed to cool down, but research shows that you should replace the cold water with hot water in the shower instead. This is because cold water causes your blood vessels to constrict, making it harder for you to lose heat. Warm water, on the other hand, opens up your blood vessels, making it easier for your body to release heat and lower your body temperature before bed. Cold water causes an immune response called the fight or flight response in the body, which increases your state of alertness. In the morning, your body temperature will slowly start to rise, preparing your body to wake up.

We sleep better when we are cooler. Therefore, keeping your body cool can lead to more deep sleep, while an overly warm environment can actually reduce deep sleep and result in less sleep overall.