Sleep Optimization: Temperature, Caffeine, Genetics, Naps + More

Take a warm bath or shower shortly before you go to sleep.

• Rapidly brings blood to the surface of the skin, forcing your core body temperature to plummet, enabling the ability to fall asleep faster and remain asleep

Temperature plays a key role in the process of waking up.

As we enter the late morning hours of sleep, particularly as we start to enter the Rapid Eye Movement (REM) sleep-​​rich phases of your sleep cycle later in the morning, the central brain temperature rises significantly.

In the last 30 minutes before naturally waking up in the morning, body temperature starts to increase. The increase in temperature is a signal that triggers the beginning of the awakening process.

Warming up the ambient temperature of the bedroom in the last 30 minutes before your alarm goes off will facilitate an easier and more effective wake-​​up process.

If you were sleeping with 65 degree Fahrenheit and you have a smart thermostat, program it to increase the temperature to around 21 degrees celsius or approximately 70 degrees Fahrenheit, in the last 30 minutes before your alarm goes off.

Alcohol harms our sleep in several different ways. Three main ways:

• Alcohol results in sedation rather than naturalistic sleep.
• Alcohol causes sleep fragmentation.
• Alcohol impairs Rapid Eye Movement (REM) sleep.

Alcohol, Sedation & Natural Sleep

Alcohol falls into a class of chemicals called sedatives.

Alcohol increases loss of consciousness and therefore the ability to fall asleep, but sedation is not natural sleep.

Natural healthy sleep is an active and highly coordinated event within the brain that occurs due to cell synchronisation, with cells working together to ‘fire’ and ‘go silent’, specifically during deep sleep.

Sleep Fragmentation

Before sleep, the body shuts off the sympathetic nervous system and shifts over to the calming, parasympathetic nervous system.

The sedative effect of alcohol switches off brain cell firing and releases several stress-​​related chemicals, including cortisol.

Alcohol spikes cortisol levels

• Usually as we fall asleep, cortisol levels in the body decrease and hit their lowest point during the middle of the night.
• After alcohol consumption, cortisol levels spike, which stimulates and reactivates the fight-​​or-​​flight sympathetic nervous system and emotional centres in the brain, forcing the brain and body back into a more hyper-​​alert state
• This makes you prone to fragmented awakenings throughout the night, which creates the feeling of not being refreshed the following morning
• Sleep becomes fragile and a less restorative process

Alcohol Affects REM Sleep

Alcohol is one of the most potent suppressors of Rapid Eye Movement (REM) sleep, also referred to as ‘Dream Sleep’.

The metabolic by-​​products of alcohol degradation within the body disrupts and impairs the generation of REM sleep.

Importance of REM Sleep

REM sleep is vital for numerous aspects of health and wellness:

• Responsible for recalibrating certain hormone systems. During REM we hit a peak in the release of important hormones, i.e. testosterone
• Lack of REM Sleep = people can suffer impairments to cognitive brain function, such as learning and creativity
• Can cause people to experience emotional stability — an increase negative moods such as anxiety
• Lack of REM sleep can also significantly impact upon lifespan longevity

REM Sleep Rebound Effect

The brain is clever and operates on a clock-​​counter system to track how much REM sleep an individual should normally have and how much has been lost due to alcohol consumption.

The brain will develop a hunger for REM sleep having been starved in the beginning and the middle of the night due to the alcohol being present in the system and as a result, will begin trying to reclaim what has been lost.

This process is called the REM sleep rebound effect.

However, the body can never accumulate all the missed REM sleep and consequently, often causes people to experience strong, intense, and vivid dreams, especially into the later hours of a sleep cycle.

An experimental sleep study found that if you gave a group of healthy adults a standardized dose of alcohol in the evening, roughly the legal blood alcohol driving limit, in the second half of the night sleep was far more fragmented.

In the last four hours of the night, participants spent 94% more time awake in comparison to when they were sober.

Caffeine is a stimulant that makes it harder to fall asleep due to its activation of the nervous system.

Caffeine makes your sleep more unstable and fragile and therefore, more difficult to stay asleep throughout the night.

This process is called sleep fragmentation, meaning that overall sleep efficiency or the consistent quality of sleep becomes significantly worse when caffeine is consumed.

Caffeine has a half-​​life of between five to six hours in the average adult, meaning that after five to six hours, 50% of that caffeine remains in the system.

Caffeine has a quarter-​​life of approximately 10 to 12 hours for a typical adult, meaning that if coffee is consumed at 2pm, almost a quarter or more of that caffeine could still be circulating in the brain at midnight.

The Quarter-​​life of caffeine varies significantly from one person to the next.

• Individuals will have varying efficiency levels of the cytochrome p450 enzyme, which is responsible for the breakdown of caffeine in the system.
• Some people will have a version of that enzyme that allows them to remove the caffeine from their system very quickly, whereas others will perform this process much slower.
• People that cannot metabolize caffeine as quickly are highly sensitive to its effects.
• It’s possible to calculate caffeine sensitivity through genetic testing kits — the two key genes to assess include CYP1A2 and AHR
  Caffeine & Sleep

Regardless of your sensitivity to caffeine, it can still subconsciously disrupt the quantity and quality of your deep non-​​REM sleep (NREM).

Caffeine will always decrease the amount of deep sleep that the brain can generate, regardless of whether an individual can fall and remain asleep or not.

Caffeine will not only make it harder to fall and remain asleep, but also increase levels of anxiety. This can lead to a cycle of caffeine dependency.

For example, drinking more coffee the next morning to compensate for poor-​​quality, un-​​restorative sleep the night before, will then diminish the quality of the subsequent night’s sleep, leading to potentially more caffeine the following day and so on.

Effects of caffeine consumption in study by Matt Walker

• The consumption of caffeine in the evening caused a decrease in NREM sleep by 20–40%.
• Without caffeine, the participants would need to age 10–15 years to replicate such results.
• 100ml of caffeine in the evening, equivalent to a single cup of coffee, will strip away more than 30% of the electrical brainwave activity in the first cycle of deep sleep.

A chronotype is the body’s natural biological preference to be awake or asleep at a certain time.

There are three main types of chronotype (Morning Lark, Night Owl, or somewhere in-between).

Unlike morning larks, night owls simply cannot fall asleep easily early at night, which leads to the first and most obvious consequence of not sleeping in line with your chronotype—you don’t sleep as much.

Morning types sleep over 7 hours per night on average, while evening types can only manage 6.6 hours of sleep per night.

• Chronic “sleep debt”; one that accrues night after night, month after month.
• The ramifications are many, including: increased caffeine intake for evening types, higher likelihood of developing hypertension and type II diabetes, and greater difficulty maintaining a healthy body weight.
• Evening types are also two to three times more likely to develop depression than their morning type counterparts, and twice as likely to be using antidepressants.

Matt clarifies that his intent in sharing the concerning statistics is not to worry evening types, but rather, to help them realize their true biological nature, and as important, not feel guilty for it.

Matt aims to vindicate and empower evening types with the knowledge that they may be sleep deprived, and to help them find a schedule that falls in line with their natural chronotype.

Matt states current societal practices push (actually, force) night owls into unhealthy sleep rhythms.

He outlines his goal of restructuring the typical schedule of work in first-​​world nations, which is strongly biased toward early start times that incorrectly punish night owls and favor morning larks.

Matt notes that this is markedly unfair, since it is not their choice as to which ‘type’ they are. Instead, it is their pre-​​ordained, genetic-​​based sleep chronotype, yet society wrongly assumes that evening types could get up earlier if only they weren’t so slovenly — this isn’t true.

Can your Chronotype change?

A three-​​week study by an Australian-​​led research team attempted to turn Night Owls into Morning Larks, with the participants following a series of strict rules over the duration.

• Setting an alarm to wake up two to three hours earlier than their normal wake time
• Eating breakfast first thing after waking up
• Getting outside for as much natural daylight as possible, and not having any caffeine after 3pm
• Results showed that by the conclusion of the study, the Evening Types went to bed roughly two hours earlier than usual, managing to get to bed around 12:30am, instead of 2:30am.
• Their performance on several standardized cognitive tasks also improved expressly during the morning hours, when Night Owls typically struggle the most.
• However, the participants were still opting to go to bed after midnight, which is far from morning Night-​​Owl-​​like, and far from being turned into a Morning Type.

It is also unlikely these individuals could continue with this rigid new set of experimental guidelines long-​​term, for their entire lifespans.

In other words, the practice may not be sustainable in the real world and instead it is recommended that we allow Evening Types to sleep in harmony with their genetic chronotype.

If Night Owls were able to sleep and wake up when they are biologically designed to, it would lead to a healthier lifestyle and environment.

Adenosine

Adenosine is a chemical signal that helps to tell the brain and body how long someone has been awake, starting when we arise.

• Adenosine achieves sleepiness using a dual action effect — high levels of adenosine turn down the volume of the wake-​​promoting regions in the brain and up in the sleep-​​inducing regions.
• The longer an individual remains awake, the greater the build-​​up of this chemical, and the sleepier someone will become
• Once adenosine concentrations peak, usually after about 12–16 hours of being awake, the irresistible urge for slumber takes hold. This process is called sleep pressure.
• Caffeine wards off the sleep pressure by artificially muting the effects of adenosine — it goes in the adenosine receptors
• However, once the caffeine wears off, you feel the sleep pressure more extremely

Removing Adenosine Through Sleep

The build-​​up of adenosine explains why, in most cases, people feel tired towards the end of the day and more awake the following morning.

During sleep, the brain has the chance to remove the day’s accumulation of adenosine

Across the night, sleep will remove the weight of sleep pressure, taking the strain off the brain

This process is usually complete after 8 hours of healthy sleep.

Longer naps can remove sleep pressure /​​ adenosine, which prevents enough sleep pressure to build to fall asleep at night.

The circadian rhythm is the 24-​​hour brain clock which regulates daily functionality — making people feel tired at night or more awake in the mornings.

Although there are numerous circadian clocks, in almost every cell of the body, there is a master clock sits deep at the centre of the brain regulating all the other body clocks.

How It Works

The circadian rhythm begins drumming out its loud activating beat shortly before an individual wakes up in the morning, continuing to get louder throughout the day, and peaking in the early afternoon.

At the end of the evening, the circadian rhythm begins to slow down, creating a drop in alertness and a rise in tiredness. This beat will hit its lowest point in the middle of the sleep phase overnight, staying low for a few hours before picking back up again.

The circadian rhythm and sleep pressure work independently, yet coincide to naturally wake up in the morning and enter full wakefulness and again in the evening to generate restorative sleep at night.

As the weight of the adenosine hits its peak, it should coincide with the downturn of the circadian rhythm, creating a perfect storm and the best possible environment for both sleep and waking.

After the peak late morning and into the early afternoon, the circadian rhythm will begin to slow down, usually around 1–4pm. This fading of physiological alertness is natural and can create tiredness but should not be a cause for concern.