Preachers and plumbers, teachers and truck drivers, cardiologists and cops, women and men, Presidents and pastry chefs, kids and adults, Christians and Muslims, Republicans and Democrats, rich and poor. Can you name something they all have in common? Everyone has to sleep.

             

Why single out sleep? Because among the many things we humans have in common, sleep is often forgotten or taken for granted. And we sometimes forget how essential it is. A person can go without food for weeks; a few days without sleep and he or she is hallucinating and unable to function. Sleep is almost as essential each day as water.

 

It is also a bit of a mystery. Adults need between seven and eight hours of sleep each day, but scientists don't really know why. Sleep seems to allow the body to restore itself and to enable the brain to organize all that has happened during the day, but these are not proven theories.

 

When we are sleep-deprived, our body makes more ghrelin -- a hormone that pushes us to eat -- and less leptin -- a hormone that tells us we've had enough. The body also produces more cortisol -- a hormone that tells our body to make more fat.

 

There seems to be an optimum amount of sleep for each person. People who sleep less have an increased risk of heart disease, obesity, and diabetes. Surprisingly, sleeping too much also carries increased risk of heart disease, obesity, and diabetes.

 

Since March is National Sleep Awareness Month, it is a good time to look at this universal human reality and see what the latest thinking and research can teach us.

Stages of sleep

Sophisticated use of electroencephalography has allowed scientists to study the brain during sleep and begin to understand the cycles of sleep. They have identified four stages. One of those stages is characterized by rapid eye movement, which they call REM sleep. The other three stages are referred to as non-REM sleep.

 

Non-REM sleep

Stage one (N1) of non-REM sleep is the state between sleep and wakefulness when the brain begins to produce theta waves. In this state the sleeper can experience "hypnagogic hallucination," which is that experience most of us have had where we seem to see things that we experienced intensely during the day. It is sometimes called the Tetris Effect. If you have played a lot of Tetris that day, you might see Tetris blocks as you go to sleep. This is also the stage when you can have the feeling of falling, or when you can suddenly jerk awake, or when you can have muscle twitches.

 

In non-REM stage two (N2), the sleep is deeper, and it is harder to awaken the sleeper. There are more theta waves, and the EEG shows something the scientists call "sleep spindles," bursts of rapid brain activity. One idea is that these spindles inhibit cognitive processes so sleep can remain tranquil. These may also have something to do with being able to sleep through loud noises. There are also "K-complexes" in this stage, a type of brain activity which may prevent the cortex from being aroused, thus keeping the sleeper asleep. K-complexes may also help in memory consolidation, a process by which memories from the day are transferred into long-term memory.

 

Stage three (N3) of non-REM sleep is very deep. The sleeper is "dead to the world," very difficult to wake up. This is slow-wave sleep, showing delta waves. Sleep-walking and sleep-talking happen in this stage.

Source: www.helpguide.org

 

REM sleep

REM sleep got its name because the eyes of the sleeper are observed to move quickly and randomly. Most of the body's muscles are paralyzed during this stage. REM sleep is also when dreams come. Perhaps it is good that the muscles are paralyzed; otherwise sleepers might act out what they are dreaming. This is sometime called "paradoxical sleep" because the brain is very active while the body is prevented from activity.

 

In a normal night you will cycle through these stages four or five times in approximately 90-minute periods. The cycle moves from N1 to N2 to N3, then back to N2, then to REM then back to N1 to start over. How long each stage lasts depends on how old you are and how long you have been asleep. You tend to do more non-REM sleep in the first few hours and more REM sleep just before you wake up.

 

Sleep disorders

According to The Answered Patient, nearly 70 million Americans suffer from a sleep disorder, though some of these may not even know there is something wrong with their sleep. A further claim is made that insufficient sleep is a U.S. epidemic. A sleep disorder may be defined as any disturbance that affects the person's ability to fall asleep or to stay asleep at night or to stay awake during the day. People of any age can have a sleep disorder-from newborns to the elderly, and scientists have found nearly 100 kinds. Here are the most common:

 

Insomnia

As many as 30 to 35 percent of adults complain of insomnia. This common condition, according to the National Sleep Foundation, has a number of forms. Acute insomnia is a brief episode of sleep difficulty caused by the stress of a particular event, like a job change, or bad news, or travel. Chronic insomnia is a long-standing pattern of sleep difficulty and arises from many causes. Comorbid insomnia is caused by a psychological condition such as chronic anxiety or depression or a physiological condition, such as arthritis or back pain. Onset insomnia is difficulty falling asleep at the beginning of the night. Maintenance insomnia is the inability to stay asleep. People with this can fall asleep but they wake up during the night and have trouble getting back to sleep.

 

Sleep breathing disorders

These have to do with the flow of air during sleep. In sleep apnea the airway of the sleeper becomes partially blocked, limiting the air getting to the lungs and often causing loud snoring, even choking sounds. The brain and body become oxygen-deprived, which may wake the sleeper. This may happen often during the night causing the sleeper to wake in the morning feeling tired. In addition to the daytime sleepiness and difficulty sleeping caused by this condition, the repeated lack of oxygen can lead to other negative consequences like high blood pressure, stroke, heart disease, and depression. Many people with sleep apnea do not know they have it. When diagnosed, it is manageable using a machine that creates continuous positive airway pressure called CPAP. An oral appliance and surgery are also options.

 

There are a number of different kinds of sleep apnea, and then there is sleep-related groaning called "catathrenia," where a prolonged sound when the sleeper exhales resembles a groan. The most common sleep breathing disorder is snoring, which occurs when the flow of breath makes the tissues in the back of the throat vibrate. It most often occurs as the sleeper breathes in, and can be caused by air flow through the nose or mouth or both. It can happen at any age, but it becomes more common as the sleeper gets older. Its worst effect is on the sleeper's bed partner, but it can sometimes be so loud it even wakes the sleeper. As noted above, snoring can also be a symptom of the more serious sleep apnea.

 

Circadian Rhythm disorders

Our "circadian rhythm" is the roughly 24-hour cycle of our internal biological processes, formed by the 24-hour day/night cycle of earth's rotation and sometimes called our "biological clock." It means at certain times of the day the body is disposed to sleep.

 

Because many people in our society travel by air, most Americans have experienced jetlag and may not think of it as a sleep disorder. It occurs when people travel across more than two time zones, causing their internal circadian rhythm to be out of sync with the intervals of day and night in the new time zone. Their internal signals tell them it's time to sleep when the external reality indicates otherwise. It takes time for the body to reset itself and then it must do it all over again when the traveler returns.

 

According to Sleep Education, "Your body uses sunlight to determine how much of the sleep-promoting hormone melatonin it produces. Melatonin production is high during the evening and very low during the day. As a result, you are alert during the daytime and sleepy at night." This is why traveling across multiple time zones can disrupt your circadian rhythms.

 

Shiftwork is a necessity for some people, but it is actually the cause of a sleep disorder. Some workers experience a disruption of the circadian rhythm. Their body wants to sleep when they have to be at work and is ready to be awake when they need to sleep. Some people adjust after a few weeks, and some never do.

 

Narcolepsy

Hypersomnia is a condition which causes the person to be excessively sleepy. Narcolepsy, the most common form, is a chronic sleep disorder where the person feels overwhelmingly tired and, in the worst case, can suddenly and uncontrollably fall asleep. About one person in 2,000 has this condition, though some are undiagnosed. It can be dangerous because it impairs the person's ability to do things which demand constant alertness, like driving a car. Narcolepsy with cataplexy involves a mix of excessive sleeping in the daytime with a condition called cataplexy where the person experiences a sudden loss of muscle tone while awake leading possibly to slurred speech, buckling knees, or in extreme cases -- paralysis, triggered by strong emotions of joy, surprise, laughter, or anger.

 

Sleep movement disorders

These are conditions that cause movement during sleep and make it hard to fall asleep and stay asleep. In restless leg syndrome a burning or itching sensation makes it hard to get comfortable enough to fall asleep. Sleep-related leg cramps happen when a muscle in the leg contracts intensely causing great pain. Bruxism is when the sleepers grind their teeth. The jaw commonly contracts in sleep, and when this contraction is too strong the teeth grind together causing them to wear down.

 

Parasomnias

These are disorders where unwanted events or experiences occur while you are falling asleep or waking up -- abnormal movement, behaviors, emotions, perceptions, or dreams. The sleeper remains mostly asleep during these and often has no memory of them. Sleepwalking is when the sleeper gets out of bed and walks around the room while still asleep. Sleep-walkers might sit up and look around in confusion. Their eyes are open with a "glassy" look. They might do routine things normally not done at night. Behavior can also be hostile or violent. It is hard to wake someone who is sleepwalking, which happens during the deep slow-wave stage of sleep and is sometimes combined with two other kinds of parasomnia-sleep-talking and night terrors or nightmares.

 

Treating sleep disorders

Restoring good sleep begins with establishing healthy sleep habits (See "How to improve your 'sleep hygiene'"). A CPAP machine is used to treat sleep apnea. Various kinds of light therapy can be used for circadian rhythm disorders. Insomnia can be treated by medication, and combining it with cognitive behavioral therapy has had positive results. There are a number of medications used to treat the many different sleep disorders. Then bringing treatment fully into the 21st century, there are software programs using wrist bands or motion-detection technology in smart phones to track a person's sleep cycles. The resulting information is used then to give feedback and to offer suggestions.

 

The goodness of sleep

Just as all humans have in common the need to sleep, all would have to agree on its benefits (see "Benefits of Good Sleep"). Miguel de Cervantes, Spanish writer of the 16th and 17th centuries who authored the classic Don Quixote, wrote, "Now, blessings light on him that first invented sleep! It covers a man [person] all over, thoughts and all, like a cloak; it is meat for the hungry, drink for the thirsty, heat for the cold, and cold for the hot. It is the current coin that purchases all the pleasures of the world cheap, and the balance that sets the king and the shepherd, the fool and the wise man, even."

Sources: sleep education.org, sleepfoundation.org