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Sleep's Effect on the Brain


Good quality sleep is one of those things that some folks take for granted because a large percentage of people never experience any problems sleeping. However, those who suffer from a sleep disorder must think about every aspect of sleep and how it may impact their health. According to one study, approximately 50 – 70 million Americans suffer from one of eighty sleep disorders. The top sleep disorders are insomnia, sleep apnea, restless leg syndrome, and narcolepsy. The American Sleep Association stated that sleep was considered a passive and dormant activity until the 1950s. During the latter part of the twentieth century, it was discovered that our brains are highly active during sleep, and a good night’s sleep is essential for good mental and physical health. Scholars agree that everyone needs sleep, but the biological purpose remains a mystery even during current times. The National Institute of Neurological Disorders and Stroke found that sleep is important to several brain functions “including how nerve cells (neurons) communicate with each other”.  This article will outline the various effects that sleep has on the brain, although sleep “affects almost every type of tissue and system in the body – from the brain, heart, and lungs to metabolism, immune function, mood, and disease resistance”.

What Really Happens During Sleep?

There is a consensus in research that shows poor-quality sleep will increase the risk of disorders like high blood pressure, cardiovascular disease, diabetes, depression, and obesity. At this point, you may be wondering what happens during sleep if your brain remains active, but your body is at rest? There are two types of sleep: rapid eye movement (REM) and non-REM. We usually go through about five stages of sleep if you count being “awake” as one stage, and the cycles continue throughout the sleep period. During a typical night, a person will go through all stages with increasingly longer, deeper REM periods occurring toward the morning.

  • Stage 1 is non-REM sleep and considered the lightest stage of sleep because the person is drifting from wakefulness. During this stage, a person’s eyes move slowly while their muscles relax, and the heartbeat slows.
  • Stage 2 is also non-REM and still considered a light stage of sleep, but the muscles relax even more. The eye movements stop, and the body temperature drops, while the heartbeat slows down even more. The brain wave fluctuations slow with occasional bursts of rapid waves, which can be measured by electrodes.
  • Stage 3 and 4 are the last parts of Non-REM sleep and is what helps us feel refreshed after waking up in the morning. This part of the sleep cycle happens in longer periods during the first part of the night. The heartbeat and breathing slow to the lowest point during this stage, and the muscles relax even more than stage 2. Brain waves slow down to the lowest point. This is considered deep sleep and is the stage when sleepwalking or bedwetting can happen in children.
  • REM Sleep is when breathing becomes faster, irregular, and shallow. A person’s eyes move rapidly in various directions, and muscles become temporarily paralyzed during sleep. The blood pressure rises while the heartbeat increases, and this part of the sleep cycle increase throughout the night while the deep sleep stage decreases.

Sleep Deprivation and Brain Functionality

It is easier to explain what happens when a person experiences poor quality sleep for an extended time or chronic sleep deprivation. We have established that there are pronounced changes in the electrical activity of the brain during sleep, and one study argues that the changes are a result of the brain’s trillions of nerve cells rewiring themselves. The brain never stops working and uses the time during sleep to detoxify, rewire, and rejuvenate.

  • Learning and Memory -The rewiring occurs during the deep sleep cycle and is needed to learn new concepts and retain memory. So, technically a person can try to learn something new, but if they lack sleep, it will be harder for the brain the process and hold on to the information.
  • Moodiness and Irritability – A good night's sleep can regulate moodiness and help a person cope with the next day's emotional challenges. According to one study, “sleep deprivation does the opposite by excessively boosting the part of the brain most closely connected to depression, anxiety, and other psychiatric disorders”.
  • Damaged Neurons – Neurons are the working cells of the brain that transmit information to other parts of the body. We can think of neurons as “essential” workers because they are needed for the body to function properly. Existing research has found that sleep deprivation evokes short-term cognitive declines. However, more recent reports have found that repeated periods of missing sleep can kill neurons.
  • Brain Detox - If sleep is deprived, the glymphatic system does not have proper time to perform flush toxins out of the brain, so toxins may build up. The buildup of brain toxins is reflected in cognitive abilities, behavior, and judgment.

How Much Sleep is Needed for Good Brain Health?

By now, you are probably wondering how much sleep is needed for optimal health, which differs from just getting by on sleep. Most adults find themselves conforming to the fast pace of society and try to get by on six or seven hours of sleep. The truth is everyone is different, and sleep requirements will vary from person to person. However, experts have come up with an average amount of sleep needed for each age group, for optimal health.

  • Newborns (0–3 months): 14–17 hours
  • Infants (4–11 months): 12–15 hours
  • Toddlers (1–2 years): 11–14 hours
  • Preschoolers (3–5 years): 10–13 hours
  • School children (6–13 years): 9–11 hours
  • Teens (14–17 years): 8–10 hours
  • Adults (18–64 years): 7–9 hours
  • Older Adults (65+): 7–8 hours


Written by: Anntonieyo Tabor

1 comment

  • Fred Durham

    Excellent commentary and facts on what happens while sleeping.

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