Sleep

Why Is Sleep Important?

Sleep is a reversible state of unconsciousness. It is achieved by stimulating the sleep-promoting neurons, which are specialized cells that transmit nerve impulses, and inhibiting the wake-promoting neurons in the brain. It is controlled by the body’s internal clock and external factors known as zeitgebers. Zeitgebers include light, atmospheric conditions, exercise, medications, and food.

Sleep is essential for memory, learning, homeostasis, and overall well-being.

What Is the Importance of Sleep for Your Mental Health?

Sleep disturbances can cause mood changes and are core symptoms of psychiatric diagnostic criteria, including major depressive disorder, bipolar disorder, and post-traumatic disorder. Disturbed sleepers report more psychiatric symptoms than normal sleepers. Many psychiatric disorders have been noted to have a component of circadian dysregulation, and this is most commonly seen in mood disorders like seasonal affective disorder and bipolar disorders.

Data examined by researchers in the Wisconsin Sleep Cohort Study showed that insomnia increases the odds of developing a new psychiatric disorder over the following year, including depression and anxiety. In most cases, a worsening sleep disorder or increased sleep disruption exacerbates any underlying psychiatric problem.

Fortunately, a meta-analysis of several trials done at Keele University, School of Psychology, and the University of Sheffield in the United Kingdom showed that improving sleep quality improves mental health.

What Happens to Your Brain When You Don’t Get Enough Sleep?

Insufficient sleep is twofold: reduced sleep quality, which is based on the time spent in the different sleep stages and sleep disruption, and the number of hours spent sleeping, which is the sleep quantity.

Sleep deprivation is common in modern society due to various factors, including work demands, social and family responsibilities, and sometimes medical conditions. About one-third of adults report sleeping less than seven hours per night on weekdays or weekends.

Acute sleep deprivation can negatively affect brain health and result in cognitive performance changes, including mental activities like problem-solving, paying attention, making decisions, and alertness. Cognitive impairment can occur in total sleep deprivation as well as sleep restriction for several nights.

Metabolic activity in the brain also drops after long-term sleep deprivation, which can lead to a slower response to stimuli. In a psychomotor vigilance test, which measures an individual’s reaction time and accuracy in detecting random numbers shown on a computer screen in a small box, there was a steady decline in performance, with more lapses, false responses, and slowed responses with chronic partial sleep deprivation.

How Much Sleep Should Adults Get?

Sleep needs decrease from birth to adulthood. The National Sleep Foundation consensus report specifies that seven to nine hours of sleep is recommended for adults aged 18-64 and older.

However, this also depends on genetic and behavioral factors. Some healthy people may require less than seven hours of sleep. This is usually associated with genetic factors, and this condition can be distinguished from insomnia by the absence of daytime impairment.

How Much Sleep Should Children Get?

The average infant requires about 14-16 hours of sleep. This amount of sleep is necessary for their brain development. At one year of age, the sleep requirement decreases to 10-14 hours. At the age of 2 years, the average sleep requirement is 12 hours, which further decreases to 10-11 hours at 4 years.

The average sleep requirement between ages 4 and 12 is 9-10 hours, and by adolescence, this duration further decreases to 8-10 hours.

Sleep supports brain development, including emotional development and physical growth spurts in teenagers.

Stages of Sleep

Physically, sleep is divided into two stages: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep.

Based on electroencephalography (EEG) criteria, NREM consists of three stages: Stage N1, Stage N2, and Stage N3.

Usually, NREM and REM sleep alternate, each cycle lasting 90-100 minutes; however, the REM stage becomes more frequent and lengthier in the later part of the sleep.

Stage Wake

Adults are typically awake for two-thirds of a 24-hour day. Open eyes, movement, and conversation can demonstrate alertness. As activities wind down, people recline and may close their eyes. This stage is when someone is getting sleepy. They are still awake, but the brainwaves slow down to a stable alpha rhythm known as the posterior dominant rhythm, a bridge between wake and sleep.

Stage N1

Stage N1 accounts for 5% of sleep time. The alpha wave rhythm, a medium-frequency pattern of brain activity associated with the restful but alert stage, decreases, and theta waves, which are slower-frequency than alpha waves, appear, marking the first sleep stage. Slow eye movements occur in the latter half of this stage.

Stage N2

Stage N2 usually comprises the largest percentage of total sleep time, typically 45-55% of the night. The electroencephalogram usually shows theta waves, sleep spindles, and K complexes in this stage.

Stage N3

Stage N3 is frequently referred to as “deep sleep.” It is characterized by low-frequency, high-amplitude delta EEG waves and typically accounts for 10-20% of the total sleep time.

Stage REM

REM sleep, also called stage R, requires three features to be determined.

• The EEG demonstrates a low-voltage mixed pattern with sawtooth waves with a 2-6 Hz frequency.
• The electrooculogram (EOG) measures the electric potential between the front and back of the eyes, demonstrating rapid eye movements.
• Electromyography (EMG), which measures muscle response to nerve stimulation, demonstrates atonia, indicating the inactivity of all voluntary muscles except the eye muscles and diaphragm.

There are two phases of REM sleep: phasic and tonic. During phasic REM, bursts of rapid eye movement and respiratory and heart rate variability occur, and some muscle twitches may occur. Muscle activity is more limited during tonic REM, with few eye movements. Dreams occur in the REM stage, which usually accounts for 20-25% of total sleep time.

Hormones and Sleep

The biological clock in a specific brain area known as the suprachiasmatic nucleus affects most neuroendocrine secretions and sleep state.

Adrenocorticotrophic-Cortisol Rhythm

The circadian rhythm mainly controls the adrenocorticotrophic-cortisol rhythm but is also affected by the sleep and wake cycle. The cortisol level decreases at the onset of sleep but rapidly increases later in the night until you wake up. Then, it slowly declines throughout the day. Partial sleep deprivation can cause reduced glucose tolerance when the cortisol level in the evening increases due to sleep deprivation.

Growth Hormone (GH)

Growth hormone is secreted during stage N3 sleep. Therefore, GH’s most significant secretory pulse occurs shortly after sleep onset. If stage N3 is reduced, GH secretion is also reduced. Sleep-related release of GH is reduced in old age.

Leptin and Ghrelin

Sleep is associated with increased ghrelin levels, an appetite stimulant gastric peptide. Leptin is an appetite-suppressant hormone produced by adipose tissue, which can rapidly increase or decrease in response to caloric intake. Leptin also increases during sleep, but the ghrelin level falls later at night despite maintaining fasting conditions. This balance prevents arousal from sleep due to hunger.

A study from the Journal of Clinical Endocrinology and Metabolism found that with sleep deprivation, there is a reduction in leptin level and an increase in ghrelin level, leading to a 24% increase in hunger rating and a 23 % increase in appetite rating in a study by Spiegel and colleagues.

Prolactin (PRL)

Prolactin is also sleep-dependent. Secretion from the pituitary gland increases 60-90 minutes after sleep onset and peaks in the early morning.

Thyroid-Stimulating Hormone (TSH)

Thyroid-stimulating hormone (TSH) is produced in the pituitary gland levels shortly before sleep onset and declines during sleep. Sleep deprivation is associated with a nocturnal rise in TSH levels.

Gonadotrophic Hormones

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH), show a pulsatile rise at sleep onset in prepuberty. LH is responsible for testosterone secretion in men, and FSH stimulates spermatogenesis. LH and FSH stimulate ovaries and estrogen/progesterone, which are responsible for menstrual cycle changes. Shift-worker increase in the incidence of infertility in women is thought to be related to an inhibitory effect on gonadotropin release during the follicular phase of the menstrual cycle.

Renin, Angiotensin, and Aldosterone

Renin is an enzyme produced by the kidneys. It works alongside two other hormones — angiotensin and aldosterone — which help with mineral balance and blood pressure. Aldosterone levels increase during sleep, and sleep deprivation can prevent the rise of its level at night, causing an imbalance.

Metabolism and Sleep

Metabolism involves two major processes- anabolism, which means building up, and catabolism, which means breaking down. Metabolism is the amount of energy the body requires to function and maintain itself. Metabolism can lead to the production of free radicals, which are unstable atoms that can damage cells.

During sleep, the metabolism slows down, and the body can deal with the damage done while awake. During normal sleep, the metabolic rate can reduce by 15% and reaches a minimum in the early morning in a circadian pattern.Sleep deprivation can cause metabolic dysregulation, including post-prandial glucose and lipid metabolism alterations.

Sleep Myths and Truths

Here are some prevailing myths regarding sleep and their corresponding clarifications.

Myth: The length of sleep is all that is important.

Truth: Both quality and quantity matter in sleep. Fragmented sleep can affect your overall well-being. Effects of poor quality and fragmented sleep can include fatigue and tiredness during daytime, lack of concentration, and gastrointestinal disturbances.

Myth: I can “sleep in” if I stay up late and have no problems.

Truth: Changing your bedtime and wake time can lead to circadian rhythm disorders. You may eventually have difficulty falling asleep or have early morning awakenings. It is essential to have a set bedtime and wake time to get consolidated sleep.

Myth: If I sleep less during the week, I can catch up on the weekend.

Truth: Sleep deprivation can lead to sleep debt, and if this deprivation continues for a long time, sleeping in on weekends will not help your body catch up with your sleep debt and fully recover from sleep deprivation.

Myth: Alcohol before bed can help you sleep.

Truth: Alcohol can undoubtedly make you sleepy and help you fall asleep, but it can cause sleep fragmentation and lead to poor quality of sleep. It can also worsen snoring and sleep apnea.

Myth: Keeping television on does not bother my sleep.

Truth: Light from the television can increase nighttime awakenings, and blue light may provide too much stimulation and prevent you from falling asleep.

Myth: If you can’t fall asleep, stay in bed until you fall asleep.

Truth: If you cannot fall asleep within 20 minutes, it is better to get out of bed, do something relaxing like reading a book or listening to music until you are sleepy, and then go back to bed. It is important to associate bed with only sleeping; if you struggle to fall asleep in bed, your mind may associate the bed with frustration and not relaxation.

Myth: Taking an afternoon nap is good for you.

Truth: Taking a nap in the afternoon can reduce the normal sleep pressure that builds up during the day to help us fall asleep at night. Napping during the day can lead to difficulty falling asleep at night and cause dysregulation of a person’s sleep schedule.

Myth: Most people talk or move while dreaming.

Truth: Approximately 80% of dreams occur during REM sleep and 20% during NREM sleep. During REM sleep, your eyes can twitch, but your body does not normally move. In persons with REM behavior disorder, the body does not stay still, and the person may make punching or kicking motions in bed. If this occurs, you need to see a healthcare provider.

What Are Some Health Risks of Not Getting Enough Sleep?

Sleep deprivation can lead to accidents and workplace errors, reduced quality of life, cardiovascular morbidity and lead to immunosuppression, and negative metabolic consequences, leading to increased risk of obesity, metabolic syndrome, and type 2 diabetes.

Additionally, cognitive impairment is most prominent in acute sleep deprivation and sleep restriction. Sleeping less than seven hours a night in laboratory settings resulted in cumulative deficits in alertness and attention. Sleep deprivation may result in a mental status that represents anxiety or depression.

Sleep deprivation can lead to circadian rhythm disorders and disconnecting sleep and wakefulness from their body temperature associations. Excessive sleepiness due to lack of sleep is a common cause of car crashes and near misses and contributes to over half of fatal truck crashes in the United States.

Short sleep duration has been associated with adverse cardiovascular effects like increased incidence of hypertension. Myocardial infarction, arrhythmias, and other cardiovascular diseases.

Chronic sleep loss is associated with increased inflammatory markers and immunodeficiency. The immune response to vaccination against influenza decreases after six days of restricted sleep. Sleep deprivation also enhances susceptibility to viruses that cause the common cold.

What Are the Common Sleep Disorders?

The third edition of the International Classification of Sleep Disorders (ICSD-3-TR), published by the American Academy of Sleep Medicine, lists seven major categories of sleep disorders, which are:

• Insomnia
• Sleep-Related Breathing Disorders
• Central disorders of Hypersomnolence
• Circadian Rhythm Sleep-Wake Disorders
• Parasomnias
• Sleep-Related Movement Disorders
• Other sleep disorders

Some disorders are easily recognizable, while others require specialized testing for accurate diagnosis.

What Are Some Tips for Better Sleep?

It’s important to get enough sleep so that your body can reap the many benefits it provides. Here are some tips for improving sleep that can easily be incorporated into a busy lifestyle:

Maintain A Sleep Schedule

Establish and maintain a daily schedule of activities every day of the week. Try to eat at regular times. Keep the same bedtime and waketime hours even through the weekend.

Exercise

Maintaining a regular daily exercise program has many benefits, including improved sleep. If you are a poor sleeper, try to do this exercise in the late afternoon or early evening; however, refrain from exercising vigorously at night.

Plan To Wind Down

Allow at least 30 minutes of wind-down time before bed. Approach bedtime as relaxed as possible. Plan to spend your evening winding down with activities that relax you. Discipline yourself not to think about stressful or upsetting thoughts before bedtime.

Journal

Use a Thought-Worry journal in the early evening to write down your thoughts so that these thoughts don’t come back to you before bedtime.

Avoid Drinking & Eating Close To Bedtime

Avoid alcohol or a heavy meal before bedtime. Avoid eating if you wake up in the middle of the night.

Sleep Cool

Keep the room where you sleep cool and dark. The ideal temperature for sleep varies by person and age, but it should be between 65-68 degrees Fahrenheit.

Avoid Screens

Avoid using electronics, including phones, laptops, iPads, and television, for 30 minutes before bedtime.

Maintain A Wake Time

Restrict time in bed to not more than 8 hours. Consider setting up an alarm clock to get up. Even if you get very little sleep, start your day at the designated time. This is the strongest signal you can give to your internal clock to set the circadian rhythm.

Try A Different Space

If you have trouble falling asleep in bed (either at the beginning or middle of the night), after you feel like it has been 15-20 minutes (do not time yourself with a clock or watch), get out of bed and the bedroom altogether. Go somewhere else in your home to do something relaxing but not engaging. Examples include reading and listening to music. Keep it relatively dark. When you feel sleepy again, return to bed to sleep. Repeat this process until your designated wake time.

Avoid Napping

Do not take naps unless your sleepiness is severe enough to impact safety, such as if you feel too sleepy to drive. Naps can reduce the amount of sleep you need at night, causing difficulty falling asleep or light sleep.

Avoid Caffeine

Avoid caffeine or caffeinated products in the late afternoon or evening.

Spend Time in the Sun

As soon as you get up or when it gets bright outside, get 30 minutes of outside light without wearing sunglasses.

Ultimately, getting good sleep is like preparing for a marathon; achieving quality rest and proper sleep hygiene requires consistent practice.

Practical Considerations for the Role of Sleep

Sleep affects all systems in the body, and good sleep is essential for emotional and physical well-being.

If you are struggling to fall asleep despite having good sleep habits or think you or a loved one has a sleep disorder, contact your healthcare provider for further evaluation.