Things you did not know about sleep

People spend a third of their time sleeping. While some go through life with the philosophy “sleep is for the weak”, science knows how important good sleep is for your health. There are some things in our everyday behavior, which affect our sleep, but conversely, sleep also affects various areas in our life. In the following, I would like to present to you some facts about sleep you may not have known yet.


Everyone knows that caffeine can help you wake up in the morning or make you more alert. But there are at least two other hidden aspects of caffeine most people do not know. Do you know how long caffeine stays in your system? If you drink a cup of coffee around 2 pm, 50% of the caffeine will still be in your system after about five to six hours. It could be that almost a quarter of that caffeine is still in your brain at midnight. As a result, it can make it harder for you to fall asleep. But not only this, caffeine also affects your brain during sleep. It turns out that caffeine can actually decrease the amount of deep, non-rapid eye movement sleep, which is important for restorative, deep sleep. As a consequence, it could be that you wake up the next morning and you do not feel refreshed, you do not feel restored by your sleep. 


It is often mistakenly thought that alcohol can be a sleeping aid. However, this is not the case. Alcohol can be problematic for sleep in three different ways. First, alcohol is considered a sedative. But sedation is not the same as sleep. In deep sleep, the brain is active and many brain cells fire and go silent together at the same time. This way, brain waves are generated. When you are sedated, none of this takes place. Sedation is a case where we are simply switching off the firing of the brain cells. This causes all the positive aspects of sleep to be lost. Furthermore, alcohol can actually trigger and activate the fight or flight branch of the nervous system during sleep. This causes you to wake up throughout the night, even if you may not notice it. As a result, you will not feel refreshed in the morning. Lastly, alcohol can block your rapid-eye-movement sleep. This kind of sleep is important for your emotional and mental health. 


Sleep is critical for learning and making new memories. Sleep makes your brain ready to absorb new information. But not only before, but also after learning, we need sleep. This is especially important for the consolidation of what has been learned. While we sleep, the same neurons are activated that were activated during the learning process. Thus, sleep is actually replaying and scoring those memories into a new circuit within the brain, strengthening that memory representation. This process is called replay. The final way in which sleep is beneficial for memory is integration and association. Sleep does not just simply strengthen individual memories; sleep will cleverly interconnect new memories together. 


Lack of sleep makes us emotionally irrational and hyperactive. Studies show that the amygdala, which is the brain structure important for emotion, is almost 60% more responsive in sleep-deprived individuals than usual.  This is due to the communication between the prefrontal cortex and the amygdala. Normally, there is good communication between the two. In sleep-deprived people, however, this connection is significantly worse. As a consequence, the amygdala is responding far more sensitively due to a lack of sleep. What is more, sleep can help you soothe difficult emotional experiences. And so, perhaps it is not time that heals all wounds, it is the time during sleep that provides that form of emotional convalescence.


There is a very intimate association between our sleep health and our immune health. Individuals sleeping less than seven hours per night are three times more likely to become infected by the rhinovirus, otherwise known as the common cold. That is because during sleep at night, the production of immune factors is stimulated. Furthermore, the body actually increases its sensitivity to those immune factors. Thus, your immune system is more robust after a good night of sleep.

Featured image:
  • Wiedmer, J., (2020). Good Night.

Author : Jessica Wiedmer