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what happens to your brain when you sleep why is sleep so important  benefits of getting enough sleep what happens when you sleep sleep and the brain

What happens to your brain when you sleep? A bedtime story of restful sleep and the brain


Sleep, like food, water, and air, is needed for survival. It is estimated that humans spend one-third of their life sleeping or trying to sleep [1]. You wake up energised and ready to take on the day after a good night’s rest. Sleep does more than just refresh you. It can make you smarter and happier by giving you a stronger and cleaner brain. 

Why do we sleep?

The origin of sleep and the brain’s need for it is still being researched. There are many theories that shed light on why we sleep [2]. It is possible that evolution developed sleep as a protective mechanism from predators and getting injured at night. Or perhaps it evolved to conserve the body’s energy in the dark due to low availability of food. Another theory states that sleep was used as a downtime for the body to repair and recover itself. One theory proposes the evolution of sleep for the brain’s growth and development. It was scheduled to produce new brain cells and connections. This could possibly explain why babies spend 14+ hours sleeping because infancy is a period of rapid brain growth.  

What happens when you sleep?

While you are blissfully drifting in the land of dreams, your brain is busy performing important functions. Your brain organises sleep in 4 stages which makes 1 sleep cycle. One night’s sleep can comprise of 4-6 cycles[3]:

  1. The first stage is a light sleep stage which lasts under 5 minutes. 
  2. The second stage is when you enter deep sleep. This comprises 45% of your total sleep time. Your brain is forming new brain connections and organising information.
  3. The third stage is the deepest sleep stage (25% of sleep time). Your body is doing repair work, building muscles and immunity. Have you experienced being awakened mid-sleep and feeling tired and groggy, despite being asleep for hours? You were likely awoken in your third sleep stage. 
  4. The final stage can last between 10-60 minutes. Your brain activity increases by 20% and this is where dreaming occurs. This is called the REM stage.

The brain chemical involved in promoting restful sleep is melatonin. Melatonin is produced in the absence of light from serotonin, your happiness brain chemical. A steady supply of serotonin is essential to maintain melatonin levels. You can ensure this by taking adequate amounts of protein building block, tryptophan, which enters the brain, is converted to 5-HTP which is then converted to serotonin. A short-cut way to produce sufficient serotonin is by intake of 5-HTP available in supplemental form for direct conversion to serotonin and finally to melatonin. The world’s smallest dense tablet of 100mg 5-HTP can naturally and safely increase serotonin levels. Read more here.

    Why is sleep so important?                               

    Sleep is subsistence and adequate high-quality sleep is essential for peak brain performance. Here are 5 benefits of getting enough sleep

    1. Deep sleep gives your brain a deep clean.

    It is difficult to focus when working in a cluttered space. Waking up to a clean room feels refreshing and provides a calming environment to work in. Something similar happens in the brain.  Your brain receives a large volume of information each second and it can process over 16 movies worth of information per day [4]. Running such an intense workflow produces waste products that must be removed. Sleep comes with a housekeeping function. Since your brain is busy working during the day, it uses the time you are asleep to do a clean sweep. Your brain is intricately designed like a maze. During sleep, the fluid surrounding the brain fills in the folds and alleys of the maze and wash away the accumulated waste materials. In fact, the spaces between the brain’s folds expand by 60% to allow the fluid to flow freely for a deep clean [5]. How refreshed do you feel after getting a good night’s sleep? You can thank your brain for washing up. 

    2. Sleep well to wake up happy.

    Have you experienced waking up after a good night’s rest and feeling good about life? There is research to back up your sleep-induced good mood. The emotion centre of your brain is connected to the area that regulates sleep. Brain scans of those with insomnia showed damage to the emotion centre, contributing to increased anxiety [6]. During the final stage of your sleep cycle, the emotion centre is reactivated to help you effectively face challenges during waking hours [7], thus contributing to a better mood. Sleeping 6-8 hours can give you a more positive outlook on life. It was found that those getting adequate sleep were better able to regulate their emotions and less likely to be affected by negative situations [8].

    3. Good sleep is your brain’s shield.

    The simple act of sleep has protective effects against everyday things like stress and serious conditions like Alzheimer’s disease. Those who slept for at least 8 hours reported 11% lower stress levels than those who slept for fewer hours [9]. When your brain gets rid of waste materials during sleep, it also clears out Alzheimer’s harmful compounds to prevent accumulation. This is also true for those who have the high-risk gene for the disease [10]. Sleeping 6-8 hours can put you in a good mood and lower your risk of dementia [12]. A review of 65 studies found that improving sleep quality among those with depression and anxiety had a positive effect on their mental health [11]. It is a good call to add “get enough good quality sleep” in your brain health to-do list.

    4. Slumber your way to a smarter brain.

    Since your brain takes in information from every source available all day, it uses the time you sleep to organise and store useful information. Just like colour-coding and labelling paperwork makes it easier to be accessed, similarly your brain “codes” information learnt during the day for better recall later. Your brain reviews information learnt during the day and transfers it from short-term storage to long-term memory during sleep [5]. The levels of your learning and memory brain chemical, acetylcholine, increase during the final sleep stage. The brain also produces new brain cells and forms new connections during sleep, and these contribute to improved memory [13]. Make sure a good night’s sleep is part of your study schedule because sleep deprivation (over 24 hours) was found to impact memory scores. It also disrupted the connections in the brain’s learning centre. It could take more than 2 nights of recovery sleep to regain memory strength and the centre’s connectivity [14].

    5. Doze away for a fitter brain

    People spend hours in the gym to stay in shape and build muscles. Your hardworking brain needs to stay in great form too. Good sleep can double as a good workout for your brain. Your brain produces new brain cells when you sleep. This is important to maintain the structure and function of the brain. An animal study found that sleep deprivation over 48 hours reduced new brain cells production by 80% [15]. Just like overdoing a gym session can be detrimental, sleeping too much can be a hindrance to brain health. A study on over 470,000 people found that the sweet spot is 7 hours, which was found to be the best for cognitive performance [16]. Your brain needs to be at an optimal size to ensure peak performance. Those who slept 6-8 hours of sleep had a bigger size of 46 important brain structures involved in memory, learning and emotions [16].

    How to get a good night’s rest?

    Practising good sleep hygiene can help you get high-quality sleep for big brainy benefits. The Sleep Foundation [17] presents good tips to help you sleep well:

    • Build a sleep-conducive bedroom environment: This includes investing in good quality bedding, avoidance of blue light that has a waking effect, and regulating room temperature to effectively turn it into a soothing space.
    • Create a regular sleep schedule: Have fixed sleep and wake times, keep daytime naps short (20 mins) and sleep for an optimal number of hours (6-8) every night.
    • Develop a bedtime routine: Preparing your mind for sleep by doing relaxing activities can help you fall asleep quicker when you get into bed.
    • Cultivate good sleep habits when awake: Limit caffeine, alcohol and smoking to avoid sleep disruptions. Being physically active can promote good quality sleep, it is recommended to stop 90 minutes before bed to allow the body to relax for your restful slumber.


    1. Aminoff, M. J. et al. (2011). We spend about one-third of our life either sleeping or attempting to do so. Handbook of clinical neurology98, vii.
    2. Brinkman, J.E., et al. (2020). Physiology, Sleep. [online] PubMed.
    3. Patel, A. K. et al. Physiology, Sleep Stages. [Updated 2022 Sep 7]. In: StatPearls
    4. Heim, S. and Keil, A. (2017). Too Much Information, Too Little Time: How the Brain Separates Important from Unimportant Things in Our Fast-Paced Media World. Frontiers for Young Minds, 5.
    5. Eugene, A.R. et al. (2015). The Neuroprotective Aspects of Sleep. MEDtube science, [online] 3(1), pp.35–40
    6. Gong, L. et al. (2019). Amygdala Changes in Chronic Insomnia and Their Association with Sleep and Anxiety Symptoms: Insight from Shape Analysis. Neural plasticity2019, 8549237.
    7. Vandekerckhove, M., & Wang, Y. L. (2017). Emotion, emotion regulation and sleep: An intimate relationship. AIMS neuroscience5(1), 1–17.
    8. Racine, C. et al. (2013). Sleep Duration, Insomnia Symptoms, and Emotion Regulation among Black Women. Journal of sleep disorders & therapy2(122), 1000122.
    9. American Psychological Association (2021). Stress and Sleep. [online]
    10. Lim, A.S.P. et al. (2013). Modification of the relationship of the apolipoprotein E ε4 allele to the risk of Alzheimer disease and neurofibrillary tangle density by sleep. JAMA neurology, [online] 70(12), pp.1544–51. 
    11. Scott, A. J. et al. (2021). Improving sleep quality leads to better mental health: A meta-analysis of randomised controlled trials. Sleep medicine reviews60, 101556.
    12. Robbins, R. et al. (2021). Examining sleep deficiency and disturbance and their risk for incident dementia and all-cause mortality in older adults across 5 years in the United States. Aging, 13(3), pp.3254–3268.
    13. Meerlo, P. et al. (2009). New neurons in the adult brain: The role of sleep and consequences of sleep loss. Sleep Medicine Reviews, 13(3), pp.187–194
    14. Chai, Y. et al. (2020). Two nights of recovery sleep restores hippocampal connectivity but not episodic memory after total sleep deprivation. Scientific Reports, [online] 10(1). 
    15. Navarro-Sanchis, C. et al. (2017). Modulation of Adult Hippocampal Neurogenesis by Sleep: Impact on Mental Health. Frontiers in neural circuits11, 74.
    16. Tai, X.Y. et al. (2022). Impact of sleep duration on executive function and brain structure. Communications Biology, [online] 5(1). 
    17. Suni, E. (2020). How to Sleep Better. [online] Sleep Foundation

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