What Does A Lack Of Sleep Do To Your Brain?

How Sleep Loss Affects Cognition: Neuroscience 101

Is there any scientific evidence that sleep loss has a negative impact on cognition? We’ve investigated!

Whether you have a demanding job, a screaming baby at home, or there just aren’t enough hours in the day to do everything you want to do, you’re not alone if you struggle to get a good night’s sleep. But, have you ever wondered what sleep loss actually does to your brain? Don’t lose any more sleep pondering over this scientific question — we’ll explain!

First off, what do we mean when we say “sleep loss” or “lack of sleep”?

There are 3 types of sleep loss:

  • sleep deprivation,
  • sleep restriction, and
  • sleep fragmentation.

Sleep deprivation is when you you haven’t had an opportunity to get some sleep in a while (Hurtado-Alvardo, et al., 2016). In contrast, the other two types of sleep loss occur when you have had time available for sleep but you haven’t been sleeping well.

For example, if you’re sleep restricted, the total amount of sleep that you’ve had and the time that’s been available for you to sleep are both less than they should be (Hurtado-Alvardo, et al., 2016). Whereas, sleep fragmentation is when you wake up several times during a period of sleep time and, thus, don’t utilize the time that you have available to sleep (Hurtado-Alvardo, et al., 2016). Make sense?

There are 3 types of sleep loss: sleep deprivation [A], sleep restriction [B], and sleep fragmentation [C]. Types B and C occur when there has been time available for sleep but sleep quantity and/or quality have not been maximized.

Before we can understand the implications of sleep loss on brain function, we need to investigate how sleep is normally regulated and what it means to challenge this natural bodily process.

The amount of sleep you get should be determined by your internal body clocks. We all have a primary body clock inside our brain, called our master clock.

Your master clock is dominant over all other clocks in your body. How so? Your master clock makes sure all of the other clocks in your organs run at the correct time. This process of internal regulation is called your sleep-wake cycle.

When you don’t sleep and wake up at the times expected by your master body clock, none of the other clocks in your body run on time. There’s a misalignment between all of your internal clocks (Wright et al., 2015). When you go against your body clocks in this way, your internal time no longer matches up with the external time of your environment.

Your sleep-wake cycle is the 24 hour daily rhythm that drives your natural sleeping patterns, as determined by the master body clock in your brain. When your behaviour goes against your body clock, it can have negative consequences on brain function.

In other words, when you sleep at a time when your body expects you to be awake, or are awake when your body expects you to be asleep, it messes up your sleep-wake cycle. This can have a negative impact on your hormones, metabolism, blood flow, immune system, bone health, stress levels, brain function, and nervous system (Wright et al., 2015).

There’s one hormone in particular that’s affected when you don’t get enough sleep — cortisol. Your master body clock does its best to keep your cortisol levels in check because cortisol influences so many other systems in your body.

However, when and how much you sleep can influence the timing of your cortisol production, as well as:

  • your stress levels,
  • when you eat and drink,
  • your physical activity levels, and
  • your exposure to light (Wright et al., 2015).

Usually, these environmental conditions are quite predictable and your master body clock is still able to keep your cortisol rhythm in check. But, when you don’t get enough sleep for a prolonged period of time, your body clocks become unsynchronized.

Just one day of sleep loss significantly increases your cortisol levels during the night, and into the first half of the following day.

Why? Sleep loss is stressful on your body and cortisol is your primary stress hormone (Wright et al., 2015). Therefore, sleep loss pushes up your cortisol levels in the morning when they are supposed to be at their lowest. You may even notice this stress, psychologically, the next day.

One day of sleep loss isn’t going to have a significant impact on your brain function. After several weeks of sleep deprivation, however, your body will no longer be able to keep up with these increased demands for cortisol. As a result, your cortisol levels will drop significantly (Wright et al., 2015).

Why does it matter if your cortisol rhythms change?

When your cortisol rhythms are altered in this way, your body clocks can become out of synchrony with each other (Wright et al., 2015). The official term for a body clock is a circadian rhythm. So, when your body clocks aren’t synchronized anymore, it’s called circadian misalignment.

Circadian misalignment is when the primary body clock in your brain is no longer able to keep all of the other clocks in your body aligned with the same internal clock time.

Many behavioural and environmental factors can influence your daily cortisol rhythm, including sleep loss. This desynchronization with your master clock can reduce cognition.

Many scientists are studying the potential implications of sleep loss and circadian misalignment. One theory is that when your body clocks aren’t aligned, your body becomes inflamed. This may explain why sleep loss is a risk factor for diseases that are characterized by excessive inflammation, such as heart disease, cancer, type 2 diabetes, and depression (Eckel et al., 2015; Irwin, Olmstead, and Carroll, 2016; Morris et al., 2016).

Hang on — what does inflammation have to do with brain function?

Scientists have unearthed so much evidence to support the idea that sleep loss impairs brain function (Hurtado-Alvarado et al., 2016). There’s a well-established link between sleep loss and cognition. And, these researchers think that the mechanism by which sleep loss influences the brain in such a way is the excessive inflammation that we just mentioned.

One scientific theory is that when you lose sleep, the barrier between your blood and your brain becomes compromised, which triggers inflammation (Hurtado-Alvarado et al., 2016). Why? Because toxins can leak into your brain that would otherwise be kept out by this protective blood-brain barrier.

At the moment, research findings are mixed, with some researchers finding increased inflammation and some finding no change in inflammation in response to sleep loss. Therefore, we can only theorize at this stage in the game when it comes to pinpointing the exact mechanisms by which sleep loss impairs brain function.

Sleep loss seems to make your blood-brain barrier leaky, contributing to excess inflammation. This could explain why sleep loss has a negative influence on memory, decision-making, and understanding complex concepts.

What do we know for certain about sleep loss and brain function then?

One thing’s for sure: sleep loss is bad for cognition (Hurtado-Alvarado et al., 2016). If you lose a lot of sleep, you can’t make new nerve cells very well, you struggle to learn new things, you’re more forgetful, and you’re not as good at making decisions (Meerlo et al., 2009; Mueller et al., 2015).

Sleep loss — whether it takes the form of sleep deprivation, sleep restriction, or sleep fragmentation — is detrimental to brain function.

This is because sleeping at the right time and for the duration that your body needs helps you:

  • process new ideas and information,
  • understand and remember new concepts, and
  • make good judgements.

There you have it. If you want your brain to be on top form, it really is crucial to get enough high-quality sleep! (Kreutzmann et al., 2015)

Written by Sophie Ash, BSc (Hons), DipION, NNCP — Research Analyst, Nutritional Therapist, and Gastrointestinal Specialist (www.onyourplate.ca).

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Sophie Ash, BSc (Hons)

Written by

Sophie is an IBS Specialist and Online Educator at On Your Plate Inc. You can take her first online course at www.udemy.com/the-fundamentals-of-ibs-management

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