Why and How to Optimise Sleep Using Practical and Scientific Tools

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The start and conclusion of every day is sleep, making it the single most important pillar of health, longevity, and human function. With a good night sleep, through optimising each sleep phase and your circadian rhythm, you will see benefits in every facet of life. A good night’s sleep can benefit mental health and physical health, specifically improving all metrics surrounding performance, cognition, the immune system, wound healing, skin health and appearance, mental clarity, life longevity, memory longevity and more.

Understanding the Phases of Sleep:

Dr Gina Poe specialises in how understanding and improving sleep can improve general function, learning, memory, and physical function. Poe describes sleep as being split into five phases: The first is when you begin to fall asleep (dozing), second is the phase between wakefulness and deep sleep, the third and fourth stage is deep, slow-wave sleep and the fifth is REM sleep (rapid-eye-movement), which is when the brain is in it's highest stage of brain activity and dreaming. Regularly, it would take the average person around 95 minutes to reach the final stage of sleep. While the body is paralyzed in this sleep state, its purpose is to stimulate the brain in order to improve memory and learning. The stages before REM sleep are most important for tissue repair and the release of hormones, this is most important in assisting muscle growth, injury repair and general pains.

The perfect night of sleep consists of 7 and a half to 8 hours, in perfect conditions you would wake after around 8 and a quarter hours, preventing the body from oversleeping. On the other hand, if you consistently deprive your sleep (four to four and a half hours) you will build up a cognitive deficit. Since sleep is the recovery of the body and the mind, your body would see far less benefits than from a complete night of rest.

Light exposure, temperature, exercise, food, and caffeine consumption are important factors in setting you up for a quality night of sleep, and they all play a part in your circadian rhythm and creating signals for your body. These factors will be discussed in the following points, and how to optimise them will be made clear and easier than you may think.

Temperature:

Regardless of wake time, your body temperature increases when you wake up each day, this in turn causes an increase in a hormone called cortisol. This hormone is known to cause stress if it is elevated for long periods of the day, however it is also associated with enhancing the immune system, increasing metabolism, focus and ability to move (hence its importance in the early hours of the day). The internal temperature of the body is dependent on its external temperature, and they work in opposition to each other, in the same way as a thermostat. Therefore, to increase the internal temperature of the body early on (increasing cortisol and waking you up), a protocol of getting the body into cold water is important (ice baths, cold shower). This is through a release of the hormone: Adrenaline. Temperature can be leveraged late at night in an opposite way to in the morning. This is through leveraging hot baths or showers later at night to lower the core body temperature. Furthermore, ensuring your sleep environment is cool will ensure your body temperature stays low for optimum sleep (reducing room temperature by around 3 degrees will do this). A hot bath or shower can also be leveraged if you are feeling too alert later in the day.

Exercise:

The most obvious way to increase the body temperature early on is through exercise, this however does not have to be an intense workout. Moderate exercise is important early on and could be in the form of a light walk or zone 2 jog (click here for the Optimise guide to zone 2). This could be easily incorporated with the next stage to optimising your circadian rhythm and thus, your sleep.

Light Exposure:

Andrew Huberman, a leading neuroscientist (Stanford), recognises the impact of light more than anything on sleep quality. He examines the following points, which have been broken down in layman’s terms. For cortisol to peak early in the day, viewing bright light is an important tool within the first 30 to 60 minutes of waking. This early viewing of light triggers a cortisol release, as neurones in the eye signal a “timer” in the body, which sets in place your sleep later in the day (this timer is your circadian rhythm). Getting light energy on your eyes is the most powerful stimulus for wakefulness during the day. As a general guide, you would need around 5 minutes of bright sunlight exposure on a clear day (looking towards but not directly at the sun), 10 minutes on a cloudy day, and as much as 20-30 minutes on an overcast day. This should be viewed without looking through a window, windshield or sunglasses, and this practice is recommended at least 80% of the time. In the same way that viewing morning sunlight tells your body to wake up, viewing late afternoon to evening sunlight does the opposite, through the different wavelengths of light in the morning versus the evening. Viewing evening light will inoculate your nervous system, communicating to your circadian clock that sleep is coming soon, this is through signals to your body and brain from the position, colour, and light intensity of the sun. Unlike the morning, in the evening hours it takes very little light to wake up the body and disrupt the circadian clock, and thus your sleep. Once the sun goes down, it is important to dim the lights in your indoor environment, ideally using only low lamps to light your home. As little artificial light as required is important for your circadian clock in the evening as it will disrupt your melatonin production (which makes you fall asleep and feel drowsy).

Caffeine:

Caffeine can be a great tool to leverage early in the day, as well as later on. However, delaying caffeine for 90 to 120 minutes after waking will force your body to avoid any afternoon “crash” in energy levels, which not only increases alertness but also allows you to avoid caffeine consumption in the afternoon hours. From 4pm, caffeine intake is not advised, especially no more than 100mg, you can then challenge yourself to delay your caffeine intake to 2 or 3pm to improve your sleep quality further. Even if you are someone who sleeps well while consuming caffeine in the afternoon or even night-time hours, data shows that caffeine intake late in the day can disrupt the architecture and quality of your sleep. Choosing when to drink coffee has an impact on our adenosine system, due to it antagonising and occupying the receptor of adenosine. The proper function of adenosine is important for sleep quality, learning, memory, motor function and ageing, and delaying caffeine intake stops the block of its proper function.

Food:

Eating early in the day increases alertness in everyone, studies show that eating early on will trigger your metabolism and increase your core body temperature, immediately increasing alertness. More importantly is what you eat, however. Eating a large meal in the early hours after waking will divert blood and other critical resources away from your brain, making you sleepier early in the day. As with the aforementioned factors towards sleep, eating consistent quality food in the morning will create a food ingrained circadian clock. Dr Matthew Walker is a key researcher and professor of the science behind sleep, and he analyses all the following factors to be important in crafting a perfect night of rest. His book, Why We Sleep provides a deep dive into the determinants and outcomes of quality sleep.

Other Ways to Optimise Sleep:

Napping in the afternoon hours, if necessary is fine to do (if you are someone who tends to feel benefits from napping). However, these should be limited to 90 minutes maximum. Intense exercise in the later hours of the day will also affect your sleep, due to the increase in temperature your body will experience from this. This in turn will delay your circadian clock, so late, intense exercise will make you want to sleep later and wake later, while earlier intense exercise will not cause the same delay to your circadian clock. Supplementation could also be an important pillar of sleep optimisation (see my article on this here) however always remember to consult a medical professional before introducing supplementation.

The set of neurones which form the circadian clock set a timer of wakefulness in place, this timer depends on the quality of all the mentioned factors, and an optimised set of factors will create successful wakefulness and alertness throughout the day. Layering these factors together will, as Walker and Huberman have described, optimise your sleep quality and your wakefulness.