Sleep and Performance: How Sleep Helps with Physical and Mental Functioning

While we sleep, our brains repair themselves, store memories, and interpret events from the day.

Light sleep, deep sleep or non-rapid eye movement (NREM) sleep, and REM sleep are the major stages of sleep, with REM being the dream state. During a restful period of sleep, the adult brain cycles through three to five sleep cycles.

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Children, especially babies, need more sleep than adults because their brains are rapidly growing and processing new information. No matter your age, getting a healthy amount of sleep every night is key to your quality of life and overall wellness.

Sleep Has a Huge Impact on Our Health

Being well-rested means you can think clearly, perform complex tasks like driving, learn new information, and even avoid common illnesses with a healthier immune system. Being under stress, getting sick with a fever, suffering a loss or major life change, experiencing poor physical health due to chronic illnesses, or struggling with a mental illness are all ways that the average American may lose sleep.

Sleep deprivation is common in the modern world, and it can impact your ability to think, regulate your mood, and be in good physical health. The average office worker’s job performance suffers when they do not get enough sleep.

Each person needs a slightly different amount of sleep every night, but the average adult requires seven to nine hours. It can take some self-mastery to get the highest quality of sleep without oversleeping or struggling with sleep deprivation.

Mental Health: Sleep, Learning, and Memory Effects

Good sleep has a huge impact on your ability to learn and remember, but the relationship between the two is not fully understood. Sleep researchers do know that both the quantity and quality of sleep impact memory and learning.

Learning and memory are usually described with three functions:

  1. Acquisition: New information is added to the brain.
  2. Consolidation: This is the process by which information becomes “stable” in long-term memory.
  3. Recall: This is the ability to access memories after they have been formed.

Losing sleep can affect each of these three steps. For example, without sufficient sleep, learning new information is harder, while finding memories of related information is also harder. Sufficient sleep helps your brain move through the whole process of taking in the new information you have learned and turning it into memories, so you can access the information easily. Sleep deprivation causes your conscious focus, vigilance, and attention to all drift.

Sleep specialists have found that there are some mild changes to sleep cycles when study participants attempt to learn new information.

  • Declarative memory: This is fact-based information that we can recall quickly. It was the subject of some of the earliest studies on sleep and its association with memory. One study focused on students learning a new language in an intensive language course. The participants were found to have an increase in REM sleep when dreams occur. Through this study, scientists hypothesized that dreams were a way for the brain to interpret events of the day and store memories. Further studies suggest that declarative memories become more ingrained if there is an emotional component to the learning process. It was less likely to impact the dream state and become a strong memory if emotions during the learning process were neutral. Slow-wave sleep (SWS), which is a deep and restorative sleep phase, also helps to process memories and events from the day. Since this is one of the longest periods during the sleep cycle, it may be the most often interrupted when a person struggles with a sleep disorder. Study results on the connection between memory and SWS have been mixed so far, so there are no definitive conclusions.
  • Procedural memory: This form of memory involves learning how to do something, like ride a bicycle. REM sleep has been found to be critical to this process through several sleep studies. Other aspects of procedural memory seem to rely on other parts of the sleep cycle. Motor learning, or specific coordinated physical movements, appear to be affected by light sleep stages rather than dreams. Visual learning appears dependent on SWS and REM sleep in relation to each other, like how long they last and how often the brain can cycle through both.

Sleep also helps us achieve “eureka!” moments during research or creative work. People who are tired may be able to go through the motions, but they have a harder time synthesizing information to create a whole thought. Those who get restful sleep are better able to access these high-level, innovative, creative parts of the mind.

Physical Health: Avoiding Illnesses and Building Muscle

You may think you can stay up late and still get up early for a session at the gym, but in the long term, you are hurting your physical health if you deprive yourself of sleep too often. In fact, you are more likely to make your physical health worse by not getting enough quality sleep.

The brain repairs itself and stores memories while you sleep. Similarly, the body repairs tissues and muscles, and synthesizes proteins, almost entirely during sleep. If you are lifting weights to get stronger, it is important to get enough sleep so your muscles can build themselves.

The most common concerns associated with sleep deprivation, especially through conditions like chronic insomnia, include:

  • Obesity. Insufficient sleep has been tied to weight gain in several studies. People who are chronically tired not only load up on caffeine, but they are also more likely to eat unhealthy food, to take in more carbohydrates than vegetables and lean protein, and to consume more calories in general. This is believed to be a way for the body to boost energy when the brain cannot focus. Medical studies have shown that people in all age groups who slept six hours or less a night were more likely to have excess body weight, while those who slept eight hours had the lowest relative body fat amount in the group. Another study followed babies into their childhood and found that those who were naturally “short sleepers” were more likely to become obese when they were older.
  • Diabetes. Type 2 diabetes and obesity are closely tied together, adding another layer to the struggles of sleep deprivation and weight gain. Getting irregular or little sleep is also associated with changes in how your body manages insulin, so there appears to be a direct correspondence between blood sugar levels and getting enough rest.
  • Hormones and metabolism. The brain manages the release of growth hormones, appetite-involved hormones, and more. Anything that changes your sleep cycle so it is irregular, causes you to get poor-quality sleep, or leads to sleep deprivation can also alter your metabolism, appetite, stress response, tissue growth, and fertility.
  • Cardiovascular disease. People who are obese and have diabetes are also at risk of hypertension, stroke, blood clots, and cardiovascular damage. While being sleep deprived can impact all these conditions and the conditions impact each other, sleep deprivation also has a direct impact on heart health. One study found that even moderately reduced sleep— for example, six hours a night instead of seven— was associated with higher levels of artery calcification, which is a predictor of future myocardial infarction (heart attack). There is also increasing evidence that sleep apnea, which can lead to sleep deprivation, among other problems, is a risk factor for heart disease, irregular heartbeat, stroke, and cardiovascular events.
  • Immune system problems. Sleep deprivation is closely associated with lower immune system function. Getting poor sleep increases inflammatory mediators, which boosts your chance of contracting an illness like the common cold. A study found that people who averaged less than seven hours of sleep per night were three times more likely to contract a cold compared to those who got adequate sleep on a regular basis.

The greatest potential source of harm from sleep deprivation is associated with slower reaction times. While this may result in feeling clumsy throughout the day, there is another more frightening side effect: poor driving.

Slow reaction times while driving increase the risk of a serious car accident. Even more frightening, a poll from the National Sleep Foundation found that a third of drivers reported that they had nodded off while driving.

Dr. Jennifer Miller, PT, DPT, says, “I have also found that my patients with poor sleep have a difficult time learning new exercises, remembering activities/exercises we’ve worked on in the past, and slower reaction and coordinating movements.”

Emotional Health: Social Connections and Reactions to Events

It makes sense that you are stressed out or cranky after losing sleep one or two nights in a row, but people who suffer from chronic sleep deprivation will also have a harder time regulating their emotions. If you struggle with insomnia, you are more likely to have depression and anxiety. Having these mental illnesses increases your risk of developing insomnia.

Your cognitive and physical performance will be impacted by being sleep deprived, and that can make you feel bad about yourself. Mood changes from being tired will also increase your chances of seeing this negative performance in a poor light since your reactions will be more intense and impulsive.

When our memory of events is impacted, we may interpret and reinterpret these events differently, which can lead us to make poor decisions. It becomes more difficult to assess situations and make plans. With aspects of declarative memory relying on an emotional connection to form stronger memories, it can be harder for a sleep-deprived person to remember and recall information accurately.

Sleep deprivation increases activity in the amygdala, which is the brain’s emotional response center. When this part of your brain is working too hard, you will feel more intense emotions about your experiences throughout the day. This can increase your stress levels, which can increase the activity in your amygdala.

Unfortunately, all this stress, worry, fear, anxiety, and anger can make it harder to go to sleep and get quality rest each night. Since sleep loss hampers the communication between the amygdala and your prefrontal cortex, which helps to regulate emotions, there is less resistance to immediate reactions in emotionally charged situations.

Not getting enough sleep also increases repetitive negative thinking, so while your amygdala’s emotional response in both positive and negative situations will be larger and less regulated, the focus of much of your emotional experience while tired will be on the negative feelings. It also becomes harder to turn your mind away from ruminating on negative thoughts when you’re tired.

Productivity at Work

The confluence of mental, physical, and emotional struggles associated with sleep deprivation can hurt your job performance and productivity.  Sleeping 10 or more hours per night may indicate poor-quality sleep, like waking up several times during the night, so this group may also be suffering from a type of sleep deprivation.

One study found that employees who slept 10 or more hours per night missed an average of 1.6 times more days of work because they got sick and lost 2.2 times more productivity. The study involved 600,000 employees across 66 companies. About 30% of adult employees reported getting fewer than six hours of sleep per night, but even those who slept more than nine hours were at risk of losing productivity.

Another study found that even mild insomnia could cause 58% greater loss of productivity at work. Those who reported daytime sleepiness experienced 50% more productivity loss. Those who snored, which is a sign of potential sleep apnea, experienced a 19% to 34% loss of productivity.

Athletes Need Good Sleep

People working desk jobs are not the only ones who need to be concerned about sleep deprivation. Professional athletes are at risk when they do not get enough sleep. The quality and amount of sleep that athletes get helps them build muscle, repair tissues, and keep their immune systems in good shape, so they can continue training.

Good sleep consolidates memories, like procedural memory, so certain physical actions like jumping or catching can be performed better. To retain those memories, getting enough quality sleep is crucial.

Some studies on athletes have found that rigorous training, especially before major sporting events, can increase cortisol levels. Cortisol is the hormone most associated with stress. When there is more cortisol in the blood, it can be harder to sleep.

Sleep deprivation decreases glycogen production, which increases the risk of fatigue, low energy, and poor focus. Not getting enough sleep impacts performance during training or the event itself, and it can be harder to recover (physically, mentally, and emotionally) afterward.

High school and college athletes, in particular, are at risk of several life stressors that make quality sleep harder to come by, which can impact their physical performance. Training and competition schedules, travel, academic demands, personal stress from friends and family, and overtraining are all risk factors for student-athletes.

At the same time, athletes demonstrate poor self-assessment ability when it comes to how well they sleep and how much rest they get. Some recommendations for coaches and trainers include helping athletes make a sleep schedule and stick to it, practice good sleep hygiene, and find ways to reduce stress in other parts of their lives.

Getting High-Quality Sleep Improves Your Life

If you practice good sleep hygiene, especially going to bed and getting up at the same time every day, you are likely to get enough rest most of the time, so you can be healthier in all areas of your life. Dr. Miller explains, “Good sleep is imperative and that’s why I often ask about my patient’s sleep hygiene during evaluation. Learning about how well they sleep allows me to make adjustments that can improve their pain, ability to retain new exercises, and feel better overall.”

While many people know that they will feel less groggy, more positive, and less physically run down, few understand that high-quality sleep actually keeps your immune system, muscles, memory, emotions, metabolism, and numerous other parts of your body healthy and in working order.

This article is for informational purposes and should not replace advice from your doctor or other medical professional.

Michelle Zhang, Wellness Writer Michelle Zhang

Michelle Zhang is a regular contributor to our Zoma blog and is our go-to sleep researcher. In her time with Zoma, Michelle has researched and published many articles on widespread sleeping habits and troubles. In her time outside of Zoma, Michelle is an occupational therapist and long-distance runner. She believes leading a healthy lifestyle is the key to getting better sleep at night. Michelle's work has been featured on Men's Journal, The Frisky, and The Mighty.

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