With knowledge of the two mechanisms that control your energy and fatigue, you can learn to adapt your day to feel refreshed and well-rested during the day and to sleep better and more soundly at night. You'll be more efficient and alert when the time is right, and more tired and sleepy when you need to sleep.
Content Developer, Psykologistuderende ved Aarhus Universitet.
Content Developer, Psychology student at Aarhus University.
Insomnia is frustrating and something that most of us experience from time to time. Some people experience it just too often. Sleep experts estimate that <hl>up to 10-15% of the Danish population suffer from severe and prolonged sleep problems.<hl>
There can be many factors at play when a sleep problem occurs. Research shows that two mechanisms, in particular, have a decisive impact on your sleep and when you feel like sleeping. The two mechanisms are:
The balance between these two factors determines how alert you are during the day and when you feel tired and ready to sleep.
Let's start by looking at the circadian rhythm: It's <hl>the natural process our brains use to regulate our sleep-wake cycle throughout the day.<hl> Your circadian rhythm is important because it controls other rhythms. This includes when you prefer to eat, your mood, your emotions, your metabolism, and the release of a wide range of hormones.
Your body has an internal 24-hour clock, located deep inside your brain. This clock creates a cyclical day-night rhythm that makes you feel tired and awake at certain times of the night and day. Your internal 24-hour rhythm is also known as your circadian rhythm. The word circadian comes from Latin and has two parts: circa, meaning approximately, and dian (derived from diem), meaning day.
We, humans, have adapted to using light. Our eyes are connected - through the optic nerve - to the back of our brain. In that part of the brain, there is a small area that controls our circadian rhythm. It's like a clock that, based on the light signals it receives, regulates the number of a lot of different hormones that affect sleep, our body temperature, and other important body functions.
Imagine you're going on a camping trip; a weekend trip with only natural light. During the day, the sun's light is absorbed through your eyes. When this happens, a signal is sent to your brain not to produce melatonin - <hl>the hormone that makes us feel sleepy.<hl> When the sun goes down and it's completely dark, the opposite signal is sent to the brain; the melatonin turns up - and as a result, we start to feel tired, and we fall asleep.
When the sun starts to rise and the light hits your eyelids, a signal is again sent to the back of your brain saying, 'stop the production of melatonin'. As melatonin production begins to slow down, we wake up ready to start a new day. The curve rises again.
When you're out in nature, the only thing that regulates your circadian rhythm is sunlight. There's only one light source your brain has to adjust to. But in everyday life, when you get light from other objects - especially the blue light from your mobile phone or television - your brain gets confused. Your brain finds it hard to tell where the light is coming from and thinks it must be the sun shining and you need to stay awake.
In short, <hl>artificial light from screens before bedtime can mean that it takes much longer for you to fall asleep<hl> because your body doesn't produce enough melatonin to help you fall asleep.
If you want to maintain a good circadian rhythm, and thus get a good night's sleep, it's important to get outside in the light - preferably every day.
To prepare your brain for sleep, it's also a good idea to turn off screens like your mobile phone and TV well before you go to sleep. Then you'll find it easier to fall asleep.
Your circadian rhythm is one of two factors that determine your wakefulness and sleep - the other is sleep pressure. For every minute you are awake, your sleep pressure increases. <hl>The longer you are awake, the more sleep pressure will build up.<hl>
Our sleep pressure is affected by both physiological and psychological things, such as how active we have been during the day and how much we slept the night before.
When sleep pressure peaks, you will have an irresistible urge to sleep - for most people this happens when they have been awake for 12 to 16 hours. As you sleep, the sleep pressure will ease. You can therefore influence your sleep pressure if you take an afternoon nap, for example, because your sleep pressure will be lower in the evening.
Most of us know that coffee contains caffeine and that it is because of caffeine that coffee is refreshing. Caffeine makes you feel more alert and awake. The reason for this is that coffee blocks the sleep pressure, so your body doesn't register the signals that it is tired. That means caffeine will temporarily block you from feeling tired.
If you drink a cup of coffee after dinner to feel more refreshed, you will inhibit your feeling of tiredness - but only for a while.
The amount of caffeine in your blood peaks around 30 minutes after consumption. Caffeine tricks you into thinking you're awake and alert. "That's very nice," you may think, but the problem is that caffeine stays in your body. That's because caffeine has a half-life of about 5 hours. That means <hl>if you drink a cup of coffee at 7.30 pm after you've eaten dinner, you'll still have 50% of the caffeine in your body at 1 am.<hl> With caffeine in your body, your body has a harder time getting into a deep sleep, which means you won't feel as rested the next day because your sleep quality has been low.
When the gap between the two curves, your circadian rhythm, and your sleep pressure, is widest, you will be most sleepy. When you sleep, your sleep pressure will quickly decrease during the night and your circadian rhythm will make sure you sleep through the night.
If your circadian rhythm and your sleep pressure are not aligned, you may find it difficult to sleep at night and feel tired during the day.
To give yourself and your sleep the best conditions for a good night’s sleep, here are 3 tips:
Everyone is different - including when it comes to sleep. The most important thing when it comes to sleep advice is to find out what works for you. What works for you may not always work for your neighbour. That's because <hl>circadian rhythms and sleep pressures are individual.<hl>
If you're tired and can't sleep, it may be a sign that you need to adjust your circadian rhythm and sleep pressure so that the two mechanisms work better together. To do this, you can use the three tips above.
