Try to remember a day when you were physically active and performed many cognitive tasks. Now imagine a day when you just chilled on your couch all day. Which day made you feel sleepier in the evening? The contrast between sleepiness after such days is at least partially explained by sleep pressure.
Sleep pressure is a phenomenon that makes us tired, sleepy and helps us to fall asleep.
Naps are truly beneficial for your energy, motivation, mental health and cognitive performance, but they can also disrupt your nightly sleep.
Help your body increase sleep pressure by getting at least 30 minutes of physical activity every day.
You can help yourself get a better night of sleep through building up your sleep pressure by avoiding caffeine late in the day, not overindulging in naps, and being physically active throughout the day.
What is sleep pressure?
Sleep pressure is a phenomenon that makes us tired, sleepy and helps us to fall asleep. Sleep pressure builds up throughout the day and makes us sleepy in the evening. From a literal sense of view, sleep pressure basically “pressures” your brain and you to sleep. This is all due to a molecule called adenosine.
Adenosine is produced as a residual product in virtually every process in our bodies, from muscle contraction and digestion, nerve cell signaling, to the production of hormones and new blood cells. Adenosine gradually accumulates in our brain throughout the day and the more adenosine accumulates, the sleepier we feel. In the brain, adenosine makes us tired and sleepy in two ways.
First, adenosine travels to the wakefulness and alertness centers of our brain, where it binds to nerve cells and slows down their activity thereby making us less alert and less awake. Second, adenosine travels to the sleep centers of our brain, where it binds to nerve cells and stimulates their activity, contributing to the feeling of sleepiness. Then, during sleep, adenosine is gradually removed from the brain and when we wake up in the morning with less adenosine in our brains, we feel refreshed and the cycle of adenosine and sleepiness begins again.
Caffeine counteracts sleep pressure
Majority of us cannot imagine our mornings without a cup of coffee. Coffee makes us feel more awake, refreshed, alert and have more energy. Doesn’t all of this sound suspiciously as the complete opposite of what adenosine does? If it does, you are completely right – caffeine in your coffee actually works its magic by acting on the adenosine system.
Caffeine is like the twin brother of adenosine. The molecular structures of caffeine and adenosine are very similar, and for our brain caffeine looks exactly like adenosine. The only difference is that when caffeine binds to the same cells that adenosine normally binds to, it does nothing more but sit there, take up space, and prevent adenosine from binding. In this manner, caffeine keeps us awake and alert by blocking the sleep-inducing effects of adenosine on our brain cells.
This is something we want in the morning and throughout the day – to stay sharp and focused – but we do not want caffeine to keep us awake in the night when we go to sleep. Caffeine is known to make it harder to fall asleep by reducing sleep pressure and also disrupt our sleep and reduce sleep quality by making our sleep more superficial which increases the probability of waking up in the night.
A common issue regarding caffeine is that many people do not know that caffeine stays in our bodies for a really long time. It takes approximately 8-10 hours on average for an average healthy adult to get rid of caffeine from their system. Therefore, I would encourage you to take your last dose of caffeine 8-10 hours before sleep and be aware of all the hidden sources of caffeine, such as sports and energy drinks, tea, cocoa and chocolate!
Naps decrease sleep pressure
Have you heard people saying that one should avoid sleeping in the daytime as it might make it harder to sleep at night? Well, that is not entirely wrong. Naps are truly beneficial for your energy, motivation, mental health and cognitive performance, but they can also disrupt your nightly sleep.
The sleepiness inducing adenosine is removed from our brain when we are sleeping. This happens no matter when we are sleeping – in the night or napping during the day. Therefore, daytime naps can actually reduce sleep pressure and make it harder to fall asleep in the evening. The trick here is the duration of the nap. Shorter than 30-minute naps have been shown to improve your memory, focus, mood and energy without any harmful consequences on the nightly slumber. However, longer naps than 30 minutes bring us to the deep stages of sleep and it is precisely the deepest sleep that removes the sleep-inducing adenosine from the brain. Therefore, napping for longer than 30 minutes might reduce your sleep pressure making it harder to fall asleep at night.
Physical activity increases sleep pressure
So, how can I build up my sleep pressure, you might ask? Well, one of the most well-established ways to increase your sleep pressure throughout the day is physical activity.
Evidence shows that physical activity helps you to fall asleep faster, improves your sleep quality and might even improve insomnia. Help your body increase sleep pressure by getting at least 30 minutes of physical activity every day. Just remember, this does not have to be some hardcore calisthenics, a walk in the morning in sunshine will do wonders! However, avoid intense workout at least 3 hours before sleep as it might activate your brain and make it harder to fall asleep.
Sleep pressure is a phenomenon that makes us tired and sleepy in the evening. Simply put, the more sleep pressure you build up through your day, the easier it will be to fall asleep and stay asleep in the night. You can help yourself get a better night of sleep through building up your sleep pressure by avoiding caffeine late in the day, not overindulging in naps, especially in the second part of your day, and being physically active throughout the day.