My recent focus on sleep

In the last weeks and months I am educating myself intensely on the topics around longevity, life span and health span. Among many things, what was fascinating for me to learn was that there was one thing which impact I have strongly underestimated. I have always believed that sleep is important. Since I started swimming as a teenager, I prioritised sleep over most other things. 

However, I was astounded to learn that I still underestimated the impact sleep has on our overall longevity. Among all the things that boost longevity, including things like nutrition, exercise, or emotional wellbeing, pretty much every expert I read about and listened to says that sleep is by far the most impactful tool we have to boost our life and health span. 

Personally, this surprised me, as I believed sleep is more or less balanced with the other tools. It seems like that’s not the case.

About one year ago, I bought a fitness tracker called Whoop to track my recovery, sleep, stress and physical strain. Looking at my metrics I luckily do well in most of them. I have a strong HRV (heart rate variability), a strong resting heart rate, high blood oxygen and a low respiratory rate. Also, I typically feel well rested and full of energy after a good nights sleep, which I most of the times have. 

However, I was surprised to notice that 1-2 sleep metrics seem to be out of the ideal zone. It’s the amount of deep sleep and REM sleep that I get. Especially my REM sleep seems to be extremely low at around 8% per night. For reference, the ideal amount is around 20-25%. Now it could be that it’s just a measuring problem and my Whoop is tracking my REM sleep inaccurately. I plan to visit a sleep labor soon to get a second view on this. 

However, it made me read and listen to a lot about what I can do to improve my sleep. Especially the podcasts of Andrew Huberman on sleep have been super helpful! I will put a link to the YouTube videos below. Here are my most significant learnings:

1. Sleep is mainly driven by two forces. First, hormonal/chemical forces including the release of stimulating hormones like cortisol, adrenaline and dopamine in the morning and relaxing hormones like melatonin in the evening. Also, a molecule called adenosine plays an important role as this molecule builds up during the day while we are awake and signals our brain how tired we are.
   
   The second force is timing, which is called the “circadian clock”. The circadian clock is more than just our natural bio rhythm. It dictates when exactly the hormones described above are released. Luckily, we humans can do a lot to influence this clock in our favour. Elements the influence the clock include things like light exposure, especially sun light and blue light, timing of exercise, timing of food intake and body temperature.
   
   
2. The circadian clock literally works like a timer. The timer starts in the morning, where it releases hormones that make you feel energetic during the day. About 12-14 hours later the timer “ends” which starts the sleepiness which makes you tired and prepares you for sleep, relaxation and recovery.
   
   IMPORTANT, how we conduct our life influences the timing of the circadian clock. This means if we do it well, it runs like a Swiss clock, giving us energy during the day when we need it, and maximises relaxation and recovery in the night. However, if we send irregular, mixed signals, the clock can get confused, which can have horrible effects. So, you want to keep the clock as much in balance as possible.  
   
   

3. After you wake up, you want to start your circadian clock as fast as possible. So, it’s important to use as many tactics as possible to get your clock going. These tactics include: 

   • Exposure to direct sunlight. Direct exposure to sunlight seems to be the most impactful tactic. This makes sense from evolutionary perspective, because before our modern lifestyle, our body would mainly use the sun (and lack of sun during the night) as information source. It’s recommended to get direct daylight exposure for at least 2-10 minutes. The cloudier the day, the longer you should stay outside. Artificial light seems to be significantly less impactful than direct daylight (about factor 10).

   • Exercise: it turns out early exercise activates your body which also helps the get the circadian clock going.

   • Body temperature: interestingly, the body cools down during the night and warms up again about 2h before waking up. To help the body heat up we can do something seemingly contradicting which is to expose the body to extreme cold. For example, in form of a cold shower or a cold plunge. This cold exposure triggers heating mechanisms, which again helps to get the circadian clock going.   

4. While the morning is all about getting the circadian clock going, the last 4-5 hours before you get to bed are all about not interfering it. Again, the circadian clock starts its sleepiness process about 12-14 hours after it started. So, if you get up at 7am and do the things described above, you will start to get tired at around 7-9pm.
   
   Stimuli that activate your nervous system should be avoided at all costs, because they interfere with the body’s wish to move towards relaxation and recovery. These stimuli include: 

   • Light exposure: you want to minimise light exposure, especially after sunset when it’s already dark outside. The sensors in your eyes are very sensitive in the evening and every kind of light sends signals to your brain that it’s still daytime, which delays your circadian clock and its mechanisms for recovery. Interestingly, exposure to daylight shortly before sunset is helpful and recommended. It signals your brain that the night is coming soon and it should prepare for sleep.

     Since it’s not practical to live completely in the dark from 7pm onwards there are a few practical tips you can use:
     1. Avoid light from above and use lights placed as low to the floor as possible. The sensors in your eyes seem to be able to understand where the light is coming from. Light from above signals your brain that the sun position is quite high, which would be the case at noon time. Low light, however, signals that the sun is low, hence it’s close to evening time. Low light seems to have a significantly less harmful impact than lights from above.
     
     2. Blue-light glasses. Like most people, I also look at screens during the evening. Be it the laptop, smartphone or TV. Wearing blue-light glasses blocks the blue light to a large degree.
     
     3. Reduce screen brigthness levels. Most screens allow to reduce the brigthness levels. Use it.

   • Exercise: late exercise activates your body, which releases activating hormones like cortisol, which are detrimental for recovery. Hence, in the evening you want to avoid heavy exercise. Relaxing exercise like yoga, breathing exercises, meditation or self-hypnosis are recommended. Heavy exercise of any form are recommended to end at least 3 hours before bed time. Personally, this was a big learning as I used to exercise late and go to bed within 1 hour after exercise. I also used to shower cold after exercise, which is detrimental as well. Now, I know why I always felt tired the day after my gym days. 

   • Body temperature: while in the morning you want to help your body to heat up by exposing yourself to cold, in the evening you want to do the opposite. You want to help your body to cool down, by exposing yourself to heat. This can be sauna, or a warm shower. As explained before, your body cools down during the night. In fact, it’s even a requirement for your body to cool down about 1°C in order to be able to fall asleep.

5. Caffeine is not a stimulant. I was mesmerised to learn that caffeine is actually not a stimulant. I thought caffeine wakes me up by stimulating my body. That seems to be a wrong assumption. Caffeines´ main mechanism works via the adenosine molecule. Reminder, adenosine is the molecule that is at its lowest after we wake up, rises during the day while we are awake and signals to your brain how tired we are.
   
   Now, in order to get that signal to the brain, these adenosine molecules need to dock on to the so called adenosine receptors. What does caffeine do? It blocks these adenosine receptors and therefore prevents the signals to get to the brain. To understand the mechanism better, imagine the adenosine receptor is a parking lot. Normally the adenosine molecule would park at the parking lot and send its signal to the brain, but if you take in caffeine, the caffeine molecule parks at the parking lot and therefore blocks the way for adenosine.
   
   What does that mean for our sleep? Well, in the morning caffeine can be very helpful to get our circadian clock going. It’s recommended to wait 90-120 minutes after we woke up to take in the first doses of caffeine, but it can be helpful. However, in the afternoon or evening we want to give caffeine the time to park out from the parking lot and make space for adenosine to show our brain our true level of tiredness. So it’s recommended to stop consuming caffeine around 10+ hours before bedtime. I typically go to bed at around 10.00-10.30pm, so my last coffee should be at around 12 noon.

Obviously there are many more details, which are all super fascinating to learn about. I therefore highly recommend to listen to Andrew Huberman and other experts. Here are my favourite three podcast episodes on sleep:

In general, sleep is a fascinating phenomena. From an evolutionary standpoint, it is the most unproductive and dangerous state any living being could experience. We don’t eat, we don’t procreate, we don’t do any activity that would lead to food or procreation and we are easy victims for any predator. But despite those disadvantages, there is not a single animal out there that can live without sleep. Every animal sleeps. So, if you believe sleep is not important think about why mother nature and evolution was not able to get rid of it?