Proper Sleep and Health
Sleep has been an active area of research for the past several decades, with its mysteries and roles in human health still not fully elucidated. What is clearly know, however, is that sleep is absolutely critical for our health. Every adult has a similar pattern of sleeping 6-9 hours during the night and some napping throughout the day with infants and children needing more sleep than adults. Most people know that it is our time to re-energize, but very few people know what sleep actually does for our brain and body and why it is a necessity for our survival. While it is very difficult to answer the question, “Why do we sleep?”, there have been different theories about why we sleep. Here, we first review scientific theories about how sleep functions to maintain normal health and subsequently break down the stages of sleep and their roles in human health.
Theories on Why We Sleep
Energy Conservation Theory – The primary purpose of sleep is to reduce one’s energy demand and metabolism during the least efficient times to look for food. This allows the body to save its energy for the times when it is easiest to search for food. Body temperature, heart rate, and caloric demand are all reduced during sleep, which lead to a reduced need for metabolic activity. This theory is believed to be related to the Inactivity Theory.
Inactivity Theory – In order to survive, animals would stay quiet and inactive during the times of vulnerability to avoid being detected by predators. This served as an advantage over other animals who remained active and, therefore, were more easily noticed. This theory is the oldest and most unpopular largely because of the counter-argument that it is better to be awake during a time of jeopardy than to be asleep so as to be able to escape danger.
Restorative Theories – The body is able to reinstate and replenish what is lost during waking hours. During sleep, the body undergoes muscle growth, tissue repair, and protein synthesis. Adenosine, a product of neuronal activities, is released and allows the body to feel tired. Sleep is also the time when most growth hormone is released. Sleep has also been associated with enhanced immune system activity. This may explain why infants and children need more sleep than adults.
Brain Plasticity Theory – Brain Plasticity is the most recent theory and is also not entirely understood, but is “based on findings that sleep is correlated to changes in the structure and organization of the brain.” It is thought that sleep affects brain activities and its performance. The brain’s plasticity is maintained by sleep and helps us learn and process. Examples include the long hours that infants sleep and what it does for their bodies and growth and adults’ amount of sleep and what it does for their abilities and performance.
While none of these theories have been proven, they do provide good leads as to why sleep is so important for us.
Stages of Sleep
Sleep consist of recurring cycles of Non Rapid Eye Movement and Rapid Eye Movement that have different functionalities and symptoms.
Non Rapid Eye Movement (NREM) (75% of the night). NREM is separated into four different stages:
- Stage 1 – Light sleep, between being awake and falling asleep. Lasts about 1-7 minutes in the first cycle.
- Stage 2 – Heart rate slows down and body temperature decreases. Sleep spindles are electroencephalographic rhythms between different parts of the brain that starts here and reoccur throughout the rest of the NREM stage. This stage usually lasts 10-25 minutes in the first cycle.
- Stage 3 – This stage is the beginning of slow wave sleep (SWS), also known as deep sleep.
- Stage 4 – SWS becomes more intense here and will last about 20-40 minutes in the first cycle. If woken up, a person may feel disoriented for a few minutes.
*Note: Brain metabolism is low in NREM, higher in REM
Rapid Eye Movement (REM) (25% of the night): Dreams occur during this time and the eyes are moving rapidly under the eyelids. This occurs about every 90 minutes after after falling asleep and reccurs throughout the night.
Physiological Response to Sleep
- Growth hormone (GH) is secreted during NREM, which promotes muscle mass and tissue repairs and also regulate growth. In children and teens, sleep helps growth and development.
- Sufficient sleep will lower ghrelin, which activates hunger, and will increase leptin, which regulates the amount of fat in the body and inhibits one’s appetite once fat reaches a certain level.
- Insulin is regulated throughout sleep. Sleep deficiency can increase your risk of diabetes.
- Some men and women may get sexually aroused during their sleep.
- Muscles become relaxed.
- Muscle mass and tissue repairs are boosted by sleep.
- Sleeping has been shown to help the body recover from illnesses.
- Less than seven hours of sleep can reduced antibody production.
Appetite and Metabolism:
- A study has shown that those who have fragmented sleep and reduced REM sleep have lower insulin in the morning and higher insulin in the afternoon. These results often lead to snacking and more frequent eating.
- Brain metabolism is higher in REM than NREM.
- Body temperature decreases.
- Heart rate and blood pressure is reduced by about 10%.
- Sleep is involved in heart repair and blood pressure maintenance.
Sleep deficiency is a broad term used to describe those who have irregular sleep, sleeping disorder, bad quality of sleep, or sleep deprivation. Sleep deprivation is an insufficient amount of sleep. The “most immediate, unavoidable effect of sleep deprivation is cognitive impairment.” Having sleep deficiency or deprivation can lead to these consequences:
- Higher chances of heart disease
- Decreased performance
- Lower alertness
- Lower libido
- Kidney disease
- Irregular heartbeat
- High blood pressure
- Increased food consumption
- Risk of obesity
- Impaired critical thinking
- Easily more irritable
Tips for Better Sleep
Sleep is one of the most important things that humans do for their brain and body. It is absolutely a necessity for your health. The recommended number of hours of sleep per day is 7-9 hours for adults, 9-10 hours for teenagers, and 10+ hours for children depending on their age. Infants need at least 16-18 hours of sleep per day for their development. Sleep deficiency is something that you will want to avoid to maintain good health. If you are having a hard time achieving adequate sleep, here are some tips:
- Turn off your electronics
- Avoid caffeine and alcohol
- Create a routine
- Take naps throughout the day
- Destress yourself
- Exercise regularly
- Eat and drink a suitable diet
- Minimize noise or use white noise if needed
- Keep your room clean
- Keep your room dark while you’re sleeping
- Be comfortable
- Do yoga
Take Away Point
While science hasn’t yet discovered the entirety of sleep’s physiological effects or even exactly why we need to sleep, we do know that sleep is a necessity for overall well-being and that it plays a major restorative role for our minds and bodies. Since we spend about one third of our lives sleeping, we might as well try to do it right.
- Header Image: Betsssssy (Flickr)
- Co-author: Shoua Kue
- Is Sleep Essential? – PLOS Biology
- The Importance of Sleep – Kathy Ostler, MD
- Why Do We Sleep, Anyway? – Harvard Medical School Division of Sleep Medicine
- Sleep Physiology – Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem
- The Stages of Sleep – Kendra Cherry, About Psychology
- Sleep Deprivation and Deficiency – National Heart, Lung, and Blood Institute Health Topics
- The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review – Obesity Reviews