Optimizing your sleep and biological rhythm
Updated: Apr 18, 2020
By Wageningen Beasts
Do you have trouble falling asleep? Are you sleeping long, but are you still feeling tired? Do you have a disturbed sleep rhythm and do you want to change it? I addressed these questions and many others in my recent lecture on sleep and rest. For members there is an opportunity to watch the lecture online (it is posted in our Facebook group under videos) in case you missed the lecture. Nonetheless, I will summarize my lecture in this article. First, I will provide some background information on sleep and rest, and afterwards I will give some tips on how to change sleep rhythm and improve sleep.
Biological clock The biological clock is a ‘system’ in the brain that regulates the daily rhythm of +/- 24 hours. As most of you might know, the biological clock plays an important role in the sleep rhythm. In humans (and many other animals), this rhythm is not exactly 24 hours. This system, also called the suprachiasmatic nucleus (SCN), which is located in the hypothalamus of the brain, is set like a stopwatch: every day it counts down 24.2 hours. This would mean that after one month of such a rhythm, your rhythm will have shifted 6 hours (30 times 0.2 hours per day). Luckily, this system (or stopwatch) is able to adapt in such a way that this clock becomes 24 hours exactly. This adaption (or entrainment) can happen because the body is able to register signals from the surrounding environment. These signals (or stimuli) tell us something about the time of the day, and are therefore also referred to as ‘zeitgebers’ (=time-givers). The most important zeitgeber is light. The SCN is able to register light, which will result in a signal of ‘day’. In the absence of light, the SCN will interpret this as ‘night’[1]. This adaptation of the biological clock, also called the pathway of light entrainment, is displayed simplistically on the picture on the right (retrieved from: https://www.nigms.nih.gov/education/pages/factsheet_circadianrhythms.aspx). Here you see that light travels to the SCN through the eyes, which will result in a message of ‘day’ in the brain.
Most of you probably have also heard of melatonin. This hormone is released in the brain (in the pineal gland (hypofyse in Dutch)) during the evening, and levels peak during the middle of the night (and are low to zero during the day). Melatonin makes you feel tired and stimulates the body to fall asleep. Therefore, melatonin plays an important role in the sleep rhythm. Melatonin is also involved in the pathway of light entrainment (which was described above). During the day, the light will tell the SCN that it is ‘day’. The SCN in turn will inhibit or block the pineal gland, which will prevent the pineal gland from releasing melatonin. During the evening, the absence of light will allow this inhibition to stop: melatonin will be slowly released, and you will become tired[2].
The eyes are especially sensitive to blue light, which means that of all colors of the light spectrum, blue light has the greatest impact on the SCN. This means that blue light gives the strongest signal to the brain that it is day[3]. Blue light is highly present in televisions, laptops, smartphones, etcetera. You might imagine, that when the eyes are exposed to a lot of blue light during the evening, this will inhibit melatonin to be released, and will result in problems falling asleep. So if you use these devices a lot during the evening, this can lead to sleeping problems.
Sleep and training The main function of sleep Is cognitive recovery; to give the brain rest, and to store the memories that are made during the day[1]. Of course the body also rests and recovers during sleep, but recovery from training also occurs during the day (when you are sitting or lying down)[4]. In addition, sleep duration does not seem to be associated to heavy exercise: top athletes do not need more sleep than non-athletes[5,6]. Thus, sleeping more is not essential in recovering from training. However: sleep deprivation can hamper recovery[7]. Thus, make sure to get your hours of sleep, but you do not need more than that. This will probably raise the question: how many hours do we need?
How many hours of sleep do we need, and how is this determined? Age is the most important determinant of how much sleep one needs. Newborns need most sleep, and elderly least. However, within the same age groups, there are large differences in how much one sleeps. How much sleep you (as an average adult) need is determined by mainly two factors: genetics and habit. It is not exactly known how important the genetic factor is, in other words: how great the difference in required hours of sleep is between persons solely due to genetic differences. However, it is known that habit can cause great differences and that the role of genetics in sleep duration is probably small[8]. All in all, no clear conclusions can be drawn on how much sleep an individual actually needs. So… now you still don’t have an answer to the question: how much sleep do you need?
Even though differences in individual sleep requirements are not known yet, one study looked at the average hours of sleep and the corresponding mortality ratio in a group of over 1.000.000 people[9]. The mortality ratio tells something about the relative chance of death, compared between groups (if you do not understand it: it can be interpreted as an indication of how healthy someone is). These mortality ratios can be seen in the figures below (retrieved from Youngstedth et al 2004[9]).
The first thing that can be concluded from these graphs is that there are hardly any differences between women and men in the mortality ratios of each group with different sleep durations. The figure also shows that people who sleep between 6.5 and 7.5 hours per night have the lowest mortality ratio and can therefore be seen as most healthy. The figure also shows that the mortality ratio increases with less than 6.5 hours of sleep, but what’s striking, is that the mortality ratio increases even more if people sleep longer than 7.5 hours of sleep. Also, on average, sleeping more than 9.5 hours a night is worse than sleeping 2.5-3.5 hours a night. Of course this is only one study, but it gives a good indication for the general population (side note: the study did adjust for lifestyle, physical activity and dietary factors).
Now there are some people who sleep 9 or even more hours a night, and if they sleep less, they are tired and not functioning. As you read before, genetics play a small role in differences in sleep duration, so this is a good example of habit. The body gets used to the amount of hours you sleep (Small intermezzo to illustrate this. Polyphasic sleep regimens are sleeping patterns during which you sleep (the most extreme example) only 2 hours per 24 hours. Every 4 hours you sleep 20 minutes. Within these 2 hours you rest as much as during a normal 8-hour night, since this sleep solely consists of deep sleep which has a higher restorative capacity. Anyone can get used to such a sleep pattern, but it takes a very long time to get used to. These polyphasic sleep regimens are a perfect example that shows that sleep is mainly determined by habit). If one would sleep 6 hours every night for many(!) nights in a row, the body will adjust the restorative capacity of sleep: one would have more restful sleep (more deep sleep, as deep sleep is most important in recovery). If one would sleep 9 or 10 hours for many nights in a row, the sleep rhythm will adjust to that: one would have relatively more light sleep (light sleep is not very important in recovery). In conclusion, even though there might be some genetic differences in how much sleep one needs, habit probably explains the large differences in sleep duration between people. Therefore, one can also change their habits and thus change their total sleep duration, which will result in more (productive) hours during the day.
How to change the sleep rhythm? Now, how can one change his sleep rhythm? You might want to change your rhythm in case you go to bed late and wake up late, and you want to advance these times, or when you want to reduce your sleep duration in case you are sleeping 9-10 hours a night, as mentioned in the last paragraph. To help you with this, I have some tips:
Be consistent! The biological clock is a complex mechanism, which is why it adapts very slowly to changes in your daily rhythm[1]. Thus, be consistent in the time you go to bed and when you wake up. Sleeping late during the weekend with the intention to catch up sleep actually disturbs your rhythm, as this is a sudden, large change for your rhythm. Also, when you want to change (advance) your sleep rhythm, try to go to bed and wake up 5-15 minutes earlier every single day.
When step 1 does not really work for you, since you are having problems with falling asleep earlier than usual, you might cold turkey your rhythm. Just set your alarm clock 1-2 hours earlier than you are used to and stick to it: wake up every day at this time. Your biological clock will have a harder time to adapt and will be disturbed due to the large change, but your body and brain will be more tired during the evening, which will aid in falling asleep. Doing this is more exhausting than option 1, as you will experience tiredness until your biological clock has adapted. Adapting completely might even take a few weeks! One important side note: when doing this, you will probably be more prone to fall asleep during the day. However, it is important you do not take daytime naps, as this will hinder sleep onset at night!
A third option that might help is melatonin. As mentioned before, melatonin is a hormone that is produced by the pineal gland in the brain and is released (secreted) during the evening. Melatonin causes the typical feeling of being tired when it is getting darker outside. This hormone is also available in supplement-form. Taking low dosages of melatonin supplements a few hours before going to sleep can stimulate and advance the melatonin production of the body[10]. This helps you fall asleep earlier and thus advance your sleeping rhythm. One important side note: do not use this chronically, and do not use high dosages. Chronic use or high dosages of melatonin can hamper the melatonin production of the body, and will result in melatonin-resistance: your body needs more melatonin to experience the same effects (due to receptor insensitivity, which basically happens when you administer any kind of drug)[1].
How to improve sleep? If you want to improve sleep (e.g. when you have trouble falling asleep or in case you are experiencing restless sleep such as frequent awakenings during the night) I also have some tips for you. Do mind, that not all of these tips are practical or feasible, but from a theoretical point of view to optimize sleep.
Increasing zeitgeber strength can make the biological rhythm stronger and the sleep cycle better[11]. This means, that when differences between day and night are greater, the body will have a stronger perception of day and night (zeitgebers). This can be done by:
Decreasing the amount of light during the evening (dim the lights of the lamps and the television).
Downloading a blue light filter on laptops and smartphones. As mentioned before, blue light exposure during the evening can inhibit melatonin release. This application filters most of the blue light from the screen, which will diminish inhibition of melatonin release.
Limiting light from entering the room during the night, by having good curtains, and switching off all the lights.
Spending the day in the light. Sunlight exposure can help, but also switching on lights inside the house when it is cloudy outside, will keep the light signals (zeitgeber strength) high.
Avoid drugs (or psychostimulants). Pretty obvious, but that doesn’t make it less important. Avoiding substances such as hard drugs (MDMA, speed, etc.)[12], but also limitation or elimination of smoking (nicotine)[13], caffeine[14,15] and alcohol[16] will help in order to optimize the nights rest. Consumption of these substances are all related to a decrease in sleep quality. A little side note for caffeine: there are large differences between persons in their sensitivity to caffeine (due to genetics and habit). This explains why some people can drink coffee during the evening without having difficulties falling asleep, while others have these difficulties when they drink coffee at 3 pm. Therefore, there are no clear conclusions about this yet, but as a general rule of thumb it is wise to avoid caffeine consumption (coffee, energy drinks) 6 hours prior to bedtime, and limit consumption of tea and soft drinks throughout the day[14,15].
Limit stress. Stress can have a great impact on sleep: falling asleep is more difficult, sleep quality is less, and it will cause feelings of fatigue during the day[17]. Limiting stress is therefore essential for optimizing sleep. However, this is easier said than done. Terminating stress from daily life can be achieved by looking at the stressor: what causes the stress? Are you able to eliminate this from your life? If it is not possible to change this stressor, it is better to change your attitude and how you perceive this stressor. Now this is quite an extensive topic, which is why we will discuss it more thoroughly in another article. For now, I can recommend meditation or yoga. A lot of people are not into this, but before dismissing it, you could give it a try. It takes some practice, but then it can be really beneficial and enjoyable. If you don’t want to try this, you might try a quick, easy tip: 4-7-8 breathing. This can be done when lying in bed when attempting to fall asleep. It is a special way of breathing that allows your mind and body to fully relax. With this technique you breathe in for 4 seconds, hold this for 7 seconds, and breathe out for 8 seconds. Do this very slowly, breathe deep into your belly and not your ribcage, and try to relax all your (facial) muscles. Doing this lowers the heart rate, relaxes the muscles, and lets the mind focus on the body instead of thoughts and will thereby help you to fall asleep more easily (this actually is the basic principle of meditation). You can look up 4-7-8 breathing on YouTube or Google for a more detailed explanation.
My last and most important tip, is to think positively. The mind and body are closely connected. People who suffer from depression are feeling physically sick and people who are happy are physically healthier than when they wouldn’t be happy. Besides this, the mind also plays a crucial role in sleep. When you think you had a good night of sleep, you will feel energetic. When you think you had a bad night of sleep, you will feel tired. Your perception of sleep influences how tired or energetic you are. A good illustration of this, is a study that looked at elderly insomniacs: elderly people who suffer from chronic sleeping problems. From all possible non-pharmacological interventions that improve sleep, Cognitive Behavioral Treatment (CBT) seemed most effective in improving sleep in these insomniacs[18,19,20]. This treatment is normally applied for patients suffering from depression, as it helps to change unhelpful thinking and behavior. Thus, CBT, which helps in thinking more positively, seems to be most effective in improving sleep and energy levels during the day. This example shows how important mindset is in sleep. My message to you: don’t worry if you have one bad night of sleep. You will be fine! Your body is well able to deal with a little less sleep every now and then. Don’t let this influence how you feel! The same goes for those people who sleep 9-10 hours a night: you don’t need this, 8 hours will be fine. It is just a matter of mindset and habituation.
I hope these tips will help you, they sure have helped me improve my sleep. Good night all!
References
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