It is well known that sleep serves many purposes in our daily lives, but there are certain hidden benefits of sleep that can be dangerously affected by depriving yourself of a good night’s rest.
Sleep: Memory and LearningEvery night during sleep, our brain collects and applies everything we have learned throughout the day. During the first phase of sleep,** delta sleep**, each daily experience that triggered an emotional response is integrated individually when brain activity slows down to its slowest frequency. The information is then stored for future memory during the second phase of sleep, when each piece of information is paired with a similar past emotional experience. This process results in dreams during the** REM period** phase of sleep.
This may be why** sleep deprivation can clearly affect learning.** When students become desperate to study, cramming before an exam and pulling all-nighters, they may actually be short-changing their scholastic performance. They stay awake all night, studying fiendishly, assuming that the material will be fresh and accessible for the next day’s exams. But if what is learned cannot be integrated into the brain due to lack of sleep, an all-nighter may not be such a good idea.
Sleep: Emotional Stability
One of the primary purposes of dreams is to desensitize you to your powerful emotional daily experiences. Sleep deprivation, especially during REM periods (routinely experienced by individuals who awaken at 4 am for a shift starting at 6 am) will result in elevated emotional instability.
There is a section of the brain more developed in humans than animals, known as the pre-frontal cortex. It plays an important role in cognitive functions, organization and prioritizing, and also with our ability to perform complex tasks. It also balances the other part of the brain known as the “limbic system,” responsible for helping us process our emotions. This interaction between the two areas of the brain develops what’s known as emotional intelligence. When we are sleep-deprived, and the pre-frontal cortex is overworked, this system fails. The overall result is that we experience increased irritability and have less aptitude to perform tasks that involve details.** Sleep: Hormonal System**
Some hormones in the body are selectively secreted or even peak during sleep. The most important is growth hormone, which peaks during the early portion of the night or during wave delta sleep. This hormone is responsible for growth in developing teenagers who are precisely the group most likely to stay up late and sleep less. Growth hormone also is responsible for cell repair and immune defenses in grown individuals. That’s why sleep-deprived people are more prone to infections and have poor defense responses during an illness or trauma.
Sleep: Metabolism and Weight Control
There are two hormones important in modulating eating behavior. Ghrelin is the hormone that makes us hungry and drives animals to seek food. Leptin is secreted by fat cells and signals the brain to feel satiation, so we sense that we’ve had enough to eat for our energy needs. For a variety of reasons, we don’t seem to be heeding those signals from our bodies, and most individuals eat for pleasure, binge emotionally or eat beyond fullness, which is why there is an ongoing obesity epidemic.
Sleep deprivation adds a new dimension to the obesity epidemic. It results in increased levels of ghrelin and decreased levels of leptin despite our energy needs or eating patterns. In addition, the pleasure center of the brain remains switched to the “on” position, so we crave carbohydrate-rich, pleasure-rewarding foods (typically processed, high in calories, fat and sodium) that will ultimately result in weight gain. Obesity can further result in sleep problems due to associated health conditions such as sleep apnea, leading to a vicious cycle that causes ongoing sleep deprivation and weight gain.
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Eli Hendel, M.D., is a board-certified internist/pulmonary specialist with board certification in Sleep Medicine. An Assistant Clinical Professor of Medicine at Keck-University of Southern California School of Medicine, and Qualified Medical Examiner for the State of California Department of Industrial Relations, his areas include asthma, COPD, sleep disorders, obstructive sleep apnea, and occupational lung diseases. Favorite hobby? Playing jazz music. Find him on Twitter @Lung_doctor.