How Sleep Affects The Brain & Why You Need To Get Enough

How Sleep Affects The Brain & Why You Need To Get Enough

Our culture is preoccupied with being busy. We work long hours, and pack every moment with activity. Often, when we do finally rest, we spend hours on our devices, scrolling through social media or watching endless hours of television. Sleep almost feels like an inconvenience, but it is critical to bodily functions and good health. 

Without sleep, we cannot form or maintain pathways in the brain for learning new skills or creating memories. Sleep affects our lungs, heart, endocrine system, metabolism, disease resistance, mood, and our immune system. Without enough sleep, we can’t concentrate or remember. (1, 2) 

Sleep And The Brain

How does our body know when to sleep? We seem to have a natural drive for sleep and wakefulness, and the body naturally moves between the two states. The circadian rhythm is a natural system that regulates wakefulness as well as other functions, while taking cues from the environment and light. The sleep-wake homeostasis drives the need for sleep. It reminds the body to sleep, and every hour the body is awake, the drive for sleep gets stronger. (1) 

The process of moving between wakefulness and sleep involves several areas of the brain that receive and send signals, produce brain chemicals, and hormones in response. The wake cycle starts in the brainstem in 2 different pathways. In the first pathway, a brain chemical called acetylcholine is released. This activates areas that signal sensory information to the cerebral cortex, the site of consciousness. In the second, other neurotransmitters like serotonin, dopamine, and noradrenaline are produced in nearby regions and enter the cerebral cortex along with other chemicals. (3) The function here is to prime the higher brain and nerve cells to interpret sensory information. (2)

Throughout the day, the body also produces adenosine triphosphate (ATP), which carries energy through cells and performs a variety of functions. As ATP breaks down, adenosine builds up and stimulates neurons in a part of the brain called VLPO. This acts almost like a dimmer switch, signaling the body to relax. At the same time, the suprachiasmatic nucleus (SCN), an area of thousands of cells in the hypothalamus, receives information from light exposure during the day. It also receives signals from melatonin from the pineal gland at night. (3)

Activation of the VLPO neurons releases another brain chemical called GABA, which stops this wake system. And the brain sleeps. We are not conscious during sleep, but parts of the brain are active with images and other activities. GABA is released in the brain stem, which relaxes the muscles and stops the body from acting out dreams. When there is enough sleep, the wake signals start and the cycle begins again. (3)

How Sleep Affects The Brain

Sleep has historically been a bit of a mystery, but we are starting to understand the implications it has on the body. Without enough sleep, the brain suffers. Our working memory and attention deteriorates. We have trouble focusing, our reaction times are slower, we have trouble recalling words, and making decisions. (4)

Chronic sleep deprivation also affects mental health. Sleep deprivation or changes in the circadian rhythms cause depression and mood disorders. (5) Research showed night shift workers had higher rates of depression, as well as ulcers, accidents, and absenteeism. (6) In fact, even one night of fragmented sleep was also shown to impair individuals’ mood, decrease mental flexibility, and attention. (5)

Disturbed sleep appears to be both a symptom of depression but also something that causes depression as well. Chronic insomnia, including complaints of 2 weeks or more of nearly every night without sleep, increases the odds of developing major depression. (7) Sleep also seems to remove toxins from the brain, which may affect neurological diseases like Alzheimer’s. (8,9)

Sleep Calculator

So how much sleep do we need? Both age and gender are a factor. Infant circadian rhythms aren’t developed and there is no concentration on sleeping and waking. Newborns sleep about 16 to 18 hours a day, and their rhythms start to increase around 2 to 3 months old. Slowly, their wakefulness increases as does their periods of sleep at night, and their sleep cycles mature. (2)

As we age, we tend to sleep less. By school age and with the introduction of social events and routines, children stop having naps, and sleep typically around 11 hours a day. With hormonal changes, adolescents still require a significant amount of sleep – about 9 to 10 hours a day. Daytime sleepiness appears to be greater during puberty, and many adolescents do not get adequate sleep. (2)

Sleep continues to change as we age, and most adults tend to start to experience earlier wake times, go to bed earlier, and have less sleep efficiency. As aging continues, slow-wave-sleep decreases by 2% per decade, and elderly people have the most disturbed sleep. (2)

Men and women generally need about the same amount of sleep, but men tend to wake more often than women and complain more often of daytime sleepiness. Women, however, tend to have trouble falling asleep but stay in slow-wave sleep longer than men. Women’s sleep patterns are also significantly affected during pregnancy and postpartum. (2)

For healthy sleep, the American Academy of Sleep Medicine recommends following these sleep recommendations: (10,11)

  • Infants 4 months to 12 months new: 12 to 16 hours, including naps
  • Children 1 to 2 years new: 11 to 14 hours, including naps
  • Children 3 to 5 years new: 10 to 13 hours, including naps
  • Children 6 to 12 years new: 9 to 12 hours per night
  • Teenagers 13 to 18 years new: 8 to 10 hours per night
  • Adults: 7 hours or more per night

Simply decide on the time you need to wake up and work backwards to estimate a lights-out time. 

Set up good habits to promote relaxation and sleep: turn off all electronics 30 minutes before lights out, take a warm shower, read a book or write in a journal, and turn the lights off at the set time. (11)

References

  1. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep
  2. https://www.ncbi.nlm.nih.gov/books/NBK19956/
  3. https://www.nature.com/articles/497S2a#article-info
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2656292/
  5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4318605/
  6. https://academic.oup.com/sleep/article/27/8/1453/2696766
  7. https://www.ncbi.nlm.nih.gov/pubmed/8679786
  8. https://www.ncbi.nlm.nih.gov/pubmed/24136970
  9. https://www.nih.gov/news-events/nih-research-matters/how-sleep-clears-brain
  10. https://aasm.org/bedtime-calculator-helps-families-prioritize-healthy-sleep/
  11. http://sleepeducation.org/healthysleep/Make-Time-2-Sleep-Bedtime-Calculator