Research has shown that along with light, temperature plays a significant role in our sleep. Changes in our body temperature has a bi-directional effect on our circadian rhythm, affecting when we naturally feel tired or alert.
As we coast towards bedtime, our internal body clock kicks off processes that begin to cool down our body temperature by 1°C, regardless of the room temperature we are sleeping in. This cooling-down of the body triggers the release of the so-called ‘sleepy hormone’ melatonin. A similar increase in temperature occurs as we come closer to morning, which limits the release of melatonin, making us feel alert and awake.
Interestingly, our circadian rhythm is so incredibly attuned to changes in our body temperature that taking steps to actively lower our body temperature can actually help us feel sleepier. We can use this to our advantage by modifying our sleep environment to facilitate better sleep.
Impact on sleep
The optimal body temperature for sleeping is around 60-70 Fahrenheit (15 to 19 °C). Fortunately, humans are endotherms, which means we are good at maintaining our body temperature stable, a process known as thermoregulation. Therefore, if we stray too far from the optimal conditions, our body responds by trying to reverse the changes. During the day, we can help respond to such changes by consciously changing our external environment, by simply taking off that extra layer, for instance.
However, as we sleep we are limited in our ability to physically change our environment. Therefore, our body has to work extra hard to self-regulate its temperature, using up a lot of energy that could be spent on ensuring we get the best quality sleep. This, in turn, may cause us to wake up feeling unrefreshed and tired the next day.
Keep it cool
Cool down your bedroom to around 16/17 °C. before you go to bed. Either by slightly opening your window or turning off the central heating, you need to facilitate your body’s cooling process to signal to your brain that you are now are ready for sleep. It may seem a little too cold, but it is the optimum temperature to help you sleep.
It may sound counter-intuitive but a warm bath helps you lose your body heat by directing warm blood to the surface, which is why we go pink. Once we step out of the warm waters into our chilly bedroom, we quickly lose all this heat through our skin lowering our core temperature. This will help your body enter the optimal temperature for sleep.
Exercising may also promote falling asleep by a similar post-exercise drop in temperature. Sweating it out between 5 pm to 9 pm is best, but avoid exercising later on, as working out pumps you with adrenaline which can prevent your body from relaxing.
Cold or hot sleeper?
Based on the layers of fat under your skin or simply your personal preferences, you may be a natural hot or cold sleeper. If you wake up every morning with all your duvets on the floor, it's probably a good idea to start using lighter bedding and wearing thinner bedclothes. Be picky with the type of material, too. For example, cotton is good at absorbing sweat from the skin and releasing the heat to the outside. Whereas duck-down material is good at keeping you warm.
Using multiple layers of bedding rather than a single duvet is always a helpful way of managing heat, as you can remove layers according to your body temperature. Hands and feet are where most of our body heat is released from, so placing them outside of your covers is ideal if you are a hot sleeper - but keep them tucked in if you tend to get cold!
Transform your relationship with the heat
In some situations, such as hot summer nights or hot flushes during menopause, it’s not always possible to change the temperature. In such cases, your reaction to the heat such as feelings of annoyance can fuel further sleeplessness but also further increase your body temperature making you toss and turn during the whole night.
Mindfully noticing where you feel hot and describing it in a neutral manner, can help you to create a mental space from which sleep can emerge, despite the heat. For example, objectively noticing the temperature and describing it in a way such as “I feel hot in my chest” can help release you from the emotional grip and increase the chance of you falling asleep, despite the heat.
Sleep cool, wake up hot
Remember, we need to be a little hotter in order for us to wake up. You can aid this process by setting your central heating to go on at a similar time to your waking up time. Not only will this send waking signals to your brain but a warm room is always easier to get out of bed in than a cold one.
If you need help overcoming insomnia , we recommend our Sleep School for Insomnia App. It contains proven tools to help you fall asleep quicker, stay asleep and wake up feeling refreshed.