Several mysteries baffle the human mind day after day and sleep are one of them. Rest is a part of our everyday life, yet there are some aspects of it we do not understand. We have not yet uncovered the causes of dreams and nightmares. We do not know how to control sleep paralysis. Rapid Eye Movement (REM) phase of sleep is possibly one of the biggest mysteries that have inspired several curious minds since the early days of science. It is a part of sleep architecture that is indispensable, yet not very well-understood. REM sleep is where we do most of our dreaming. To screen colorful pictures our brain requires a lot of energy. This state of sleep is shared among all warm-blooded mammals, although the high energy demand makes its benefits challenging to understand.
What is REM sleep?
There have been several successful studies involving the drug-induced suppression of the REM state. It has shown no significant effect on the behavior of the mammal during its waking phase. Since the discovery and categorization of this stage by Eugene Aserinksy, it has been about five decades, and no adaptive functions of it have come to the surface. Over the last couple of years, neurologists and sleep experts have unearthed the neural circuitry that is responsible for the maintenance of the different stages of sleep. Even that has not helped in unveiling the mystery of the evolution of REM sleep.
Nonetheless, all mammals dream and some of us even see the meaning behind those dreams. REM sleep is ubiquitous among infants and children, but they do not report dreams until they are about 4 to 5 years old. It is one of the four stages of sleep in human beings, and REM recurs every 90 minutes or 1.5 hours in people without any sleep disorders. A complete sleep cycle consists of 4 non-REM stages interspersed with a REM stage. We experience about 4 to 5 REM stages during 8 hours of sleep, and each one is successively longer than the previous ones. It is the reason scientists often refer to our resting state as paradoxical sleep. That is because our brains are more active during this stage of sleep than it is during wakefulness.
What is NREM sleep?
Non-REM or NREM phases consist of high voltage slow wave sleep that is usually dreamless. We experience 3 of these stages, increasing in depth successively, that leads to REM sleep. That means almost 80% of our nighttime rest is non-REM and dreamless. Scientists have divided this stage into N1, N2, and N3 stages. Dreaming during any of these stages is very unlikely. During non-Rapid eye movement sleep, the upper airways become floppier and the sleeper experiences weaker muscle contractions due to lower levels of calcium. Loud breathing and snoring are common signs of NREM sleep. The problem of collapsing airways is especially predominant in overweight individuals, whose fat deposits weigh down on the respiratory tract.
Almost all the common sleep-related problems including sleepwalking sleep talking, sleep sex, nightmares, night terrors and sleep eating are NREM parasomnias. These occur when a physiological signal triggers “awakening” in the brain when it is sound asleep. You can think of it as a state between full sleep and awakening. These are more common during slow wave sleep (SWS) or the deepest NREM state than in REM. During the N3 stage, a person often faces significant difficulty while waking up or responding to alarm calls. It induces “sleep inertia” – a state of confusion among all ages upon awakening from the deep N3 state.
What are the contributions of rapid eye movement sleep to health?
The Rapid Eye Movement stage of sleep has been the topic of several studies, publications, and seminars. We do not know a lot about the complete set of functions REM sleep might have. Some propose it has restorative functions and others often state that it boosts the conversion of short-term memory to long-term memory. Some experiments prove that rapid eye movement is necessary for increasing the chances of survival in mammals. Certain viruses suppress this stage and decrease the life expectancy significantly. Researchers do not understand the precise mechanism and functions of REM, but several theories help –
Have you noticed how cramming notes the night before the exam always made you feel confused? Research shows that sleep is the only tool that can convert short-term memory into long-term memory. People, who take time in preparing for their exams often score better because they get the much-needed nighttime sleep on the night before. REM sleep, in particular, aids spatial memory, emotional memory, and procedural memory. In human beings, REM stage helps with learning new movement techniques and problem-solving methods. Deprivation of this stage of sleep shows impairment of factual memory. However, contradictory studies using people with suppressed REM and antidepressants that eliminate REM sleep show little to no proof of a deteriorating memory.
REM occurs less with age. It is most common among neonates since it helps in brain development. The deprivation of enough rapid eye movement sleep in the early years can result in behavior problems, a decrease in brain mass, problem with neural connections, permanent disruption of sleep and premature death of neuronal cells.
Fresh oxygen to the cornea
Dr. David Maurice of Columbia University proposed a theory that stated REM aids in the supply of oxygen to the cornea. According to his hypothesis, the aqueous humor, or the fluid between the iris and cornea remains static unless it receives external stimulus. REM stage provides sufficient movement that stirs the liquid and facilitates the diffusion of oxygen. It is consistent with the observation of REM stages in new-born babies and fetuses.
According to the Sentinel Hypothesis by Frederick Snyder, in 1966, certain mammals like the hedgehogs, rabbits and rhesus monkeys often awake after a brief period of REM sleep. Even human beings are more likely to wake up after a rapid eye movement stage, rather than after a slow wave sleep state. That might be an evolutionary adaptation that helps the animals scan their environment periodically for predators. He stated that this state results in the periodic activation of the mammal. However, his theory does not explain the muscle paralysis, experts associated with the REM state.
Increases energy reserve in the brain
During the REM stages of sleep, the hippocampus becomes especially active. It facilitates the refill of ATP (main energy currency in mammals) in the hippocampus and other brain structures. In healthy young human adults, the level of blood glucose periodically increases right before nighttime sleep due to controlled changes in the hormone levels. During NREM stages, the concentration of glucose in the brain increases and this signifies the beginning of the ATP synthesis process that occurs during REM sleep. Several interconnected events ensure the availability of glycogen (glucose form) for the synthesis of the tri-phosphate energy molecules.
A recent publication in the Journal of Immunology Research points towards pathogen-mediated modification of NREM and REM sleep states. In fact, people, who do not get complete rest every night are more susceptible to several viral and bacterial infections including the flu. Greater susceptibility to one or more of these infections has a direct link with sleep deprivation. Sleep and immunity have a two-way relationship that helps our body combat viral and bacterial infections, and parasitic attacks.
Compensates for reduced foraging
Jim Horne is a sleep expert and researcher at the Loughborough University. He suggests that REM sleep in modern human beings helps in compensating for the significant decrease in the need for foraging during the night.
Many research groups and well-known sleep experts are still there, who believe that REM sleep does not serve any particular purpose. They think that this phase is a result of accidental brain activation during sleep.
How much do we know about the different stages of REM sleep?
According to the sleep experts, REM sleep has several stages as well. The tonic REM sleep, phasic REM sleep, effort and arousal are the four stages experts commonly mention in studies of sleep phases. Each of them has a few shared traits and a few differences. Tonic REM sleep and effort share maximum physiological similarities.
Here are a few traits that tonic REM and effort share in the human subject –
- There are periodic dilation and constriction of pupils during these stages.
- The heart rate of the subject decelerates.
- There is a desynchronization of the ECG.
- The activity of rhythmic theta waves increases during these stages.
- The activity level in the hippocampus increases.
The phasic REM and arousal stages have several shared traits as well. These include –
- An acceleration of the heart rate.
- There is a significant increase in the blood pressure level.
- There is a prominent rapid movement of the eyes.
- Subjects can go through fluctuations in respiratory functions.
- They also experience increased electro-dermal activity.
- The amygdala becomes more active during these stages.
Closer study of these stages shows that REM sleep facilitates the mobilization of ATP in certain parts of the brain associated with memory, emotion, and creativity.
Have you ever felt the sweet relief sleep brings after days of staying up late or not getting enough sleep? Sleep deprivation brings forth REM rebound. That is usually the rapid cycling of sleep into the REM stage after experiencing several nights of sleeplessness. The brain tends to accelerate to this stage and remains in a period of extended rest during a REM rebound.
When can you call yourself sleep deprived? When you experience lesser than 2 hours of sleep per night, you are suffering from sleep deprivation. A severe lack of restorative sleep can increase the REM cycle by 20% of the normal REM duration. Therefore, you could experience a 24-minute increase in REM at least. Our brains tend to make up for lost restorative sleep, and this significant increase shows the presence of REM rebound.
Not getting enough sleep is usually a side effect of sleep apnea. People, who undergo CPAP treatment for the first time often experience REM rebound. However, this increases the risk of hypoventilation in patients with severe obstructive sleep apnea (OSA).
The lack of enough REM sleep can result from late work hours, shift changes and other dietary problems. One way to ensure that you are getting enough restorative sleep is by recalling your dreams. If you can recollect your dreams to a significant degree each night that signifies that you are getting enough refreshing sleep. The lack of it can cause excessive fatigue, muscle ache, and mood swings. It decreases physical performance and mental capacity in the long run.
Dreams are the expression of the mind. They are mental activities, and they should not exhaust us after a night’s sleep. Have you ever tried to catch a ball in your sleep because you were dreaming about playing catch? Have you ever acted out any of your dreams? There are people, who walk, talk and move about in the bed while they dream. If you know someone who talks, screams, cries or even laughs in their dream, they might be suffering from REM sleep behavior disorder (RBD).
People with RBD often suffer injuries from one of their episodes, and they are always at risk of injuring their co-sleepers. We usually dream during the REM state. During this phase of sleep, our brains exhibit electrical activities similar to the waking stage. However, there is temporary muscle paralysis that prevents us from moving about during this phase. In the event of an RBD episode, the neurological barrier between these sleep stages usually breaks down. The increasing blurring of the distinction between the periods causes the loss of temporary muscle paralysis. One state invades another in little-understood mechanisms.
RBD: what does it mean for the patients?
Experts don’t yet know what causes RBD, but several studies show its association with neurodegenerative diseases like Huntington’s, Alzheimer’s, Parkinson’s, diffuse Lewy body dementia, Shy-Drager syndrome and multisystem muscle atrophy. Almost 55% of the cases of reported RBD do not have any particular trigger, but 45% of the cases result from alcohol abuse, withdrawal from antidepressants and sedatives. Another study shows that about 38% of the cases of RBD develop Parkinson’s in the later years. RBD and Parkinson’s share a complicated relationship, but not all with this sleeping disorder necessarily develop Parkinson’s.
Several factors can increase your chances of developing RBD.
- You are male, and you are over 50 years of age – women suffer from this sleep disorder, but middle-aged men are always at high risk. In the recent years, children, teenagers, and young adults have been reporting cases of RBD. Examples of brain tumors (pre-op and post-op) usually increase the chances of RBD irrespective of age and sex.
- You have narcolepsy: it is a chronic sleeping disorder that begins with excessive daytime sleepiness (EDS). Narcolepsy Type 1 and Type 2 increase the risks of a person developing RBD.
- You are taking certain types of medications: tricyclic antidepressants tend increasing instances of RBD. Withdrawal from sedatives and addiction to alcohol often exacerbates cases of REM sleep behavior disorder.
There are multiple personal risk factors and environmental factors that contribute to the development of REM sleep behavior. These may include exposure to pesticides, unattended head injury, hemorrhaging due to strokes, smoking or drug abuse. If you suffer from a parasomnia like this you should always consult a sleep expert or with your doctor for better management of your sleep-movements. If you someone in your family suffers from RBD, always ensure that the window next to their bed is locked, their beds are low and that their sleeping area is devoid of sharp object.
Pharmacology and its effects on REM sleep
Experts have seen and studied the effects of prescription medication on REM sleep. All the popular antidepressants, sleeping medications, and other psychoactive drugs have a significant impact on this stage. In a healthy individual, a sharp decrease in the level of noradrenaline and an increase in acetylcholine indicate the beginning of the REM stage. These drugs work by increasing cholinergic activity. It is not at all surprising for a person on any one or more of these drugs to have more vivid dreams. It is also a typical experience for people on nicotine patches. Nicotine stimulates cholinergic activity, just like the modern drugs that can treat Alzheimer’s. Galantamine, memantine, and donepezil are such medicinal compounds that work by increasing the levels of acetylcholine in the forebrain.
There is another category of drugs that can affect the REM sleep by exercising their effects on NREM sleep. Benzodiazepines and Z-drugs work by repressing the shortwave sleep (SWS) in patients. They disrupt the cycle of sleep to such an extent that SWS and REM antagonize each other. There can be a dis-inhibition of REM that can cause vivid nightmares, which are characteristic for withdrawal syndromes. Cocaine addicts suffer from suppression of REM sleep and alteration of serotonin-based transmissions. That results in REM dis-inhibition, and unpleasant dreams as the drugs wear off.
Almost all mood-altering drugs and medications have similar effects on sleep. Several serotonin reuptake inhibitors (a class of antidepressants) can have similar symptoms upon withdrawal. Patients taking SSRIs often report experiencing vivid, bizarre and intense dreams that can last the entirety of their sleep. On the contrary, people taking monoamine oxidase inhibitors (MAOI) suffer the loss of their ability to dream for extended periods.
Alcohol and REM sleep have never seen eye-to-eye
In case of extreme cases of alcohol abuse, people suffer from 100% dis-inhibition of REM. During the withdrawal stages, patients can lose complete control over the REM and NREM cycles. It unleashes a flood of delusions and sporadic anxiety attacks. Alcohol affects the quality of sleep drastically. Few pegs of liquor can stimulate endorphins and help you fall asleep. Experts often state how a glass of wine with dinner or some sherry after dinner is fine for health, but at the same time, they warn you about the deleterious effects of alcohol on your health. Alcohol increases the alpha wave activity and delta waves during sleep. Together, these wave patterns can inhibit restorative sleep.
Prolonged alcohol abuse can result in disruption of your circadian rhythm. It can lead to many sleeping disorders including several parasomnias, advanced sleep onset, delayed sleep onset and excessive daytime sleepiness. Hypersomnia is also common among people with a history of alcohol abuse. Heavy drinkers often fall asleep on their feet and wake up during the latter part of the night feeling tired but sleep deprived. It often exacerbates cases of OSA and other breathing problems that can inhibit proper restorative sleep. Additionally, alcohol dehydrates the body fast, and it can trigger the urge to urinate. People, who regularly drink before bedtime often have to get up in the middle of the night to pee. It is primarily a problem for diabetic people.
In short, alcohol has many harmful effects on the sleep quality and quantity. A nightcap may help you fall asleep quicker than before, but it will also wake you up before you have completed your rest. Confusional awakenings are frequent in such cases.
What are the essential functions of the deep restorative sleep?
We come across several REM suppressants in our daily lives. Alcohol, sleeping pills, antidepressants, and cannabis are standard tools of quick sleep onset, but at the same time, they trigger chemicals that block REM sleep. People often inquire about the effects of restorative sleep and the lack of it. Here are a few facts you might experience if you are not getting restorative sleep on a regular basis –
- Emotional regulation: People often feel more irritable, and you are more likely to fly off the handle at the slightest provocation without restorative sleep. Depression is just one of the effects of the lack of REM. Dreaming is very important since our brains cope with the day’s stress and emotional duress at the simultaneously. It is common among people with sleep apnea.
- Increased localized swellings and pain: The lack of restorative sleep can increase instances of joint pain, muscle fatigue and occasional headaches. A migraine increases with the lack of REM sleep. People, who suffer from REM suppression, suffer from a significant increase in inflammatory responses.
- Distorted glucose metabolism: The lack of full sleep causes glycogen buildup in the body. The brain utilizes less energy due to the absence of the dream state. It creates an increase in the blood glucose levels. It impairs the glucose utilization and breakdown metabolisms in the human body. The lack of REM sleep can increase the risk of diabetes in adults. Additionally, those suffering from high levels of blood glucose or insufficient insulin metabolisms often suffer from obesity.
- Increasing risk of dementia: Middle-aged people, especially men, suffering from a chronic lack of REM sleep often have late-onset dementia. They are at higher risk of developing the disease than those, who get their restorative sleep daily.
- Miscellaneous effects: A popular publication by Dr. Patrick McNamara shows that REM contributes to the increase of anxious depression, mood instability, biased memory processing and loss of memory. Proper sleep can restore mood disorders and improve cases of anxious depression.
How can you improve your REM sleep quality?
These provide us with plenty of reasons to improve our sleep quality. Both REM and NREM sleep can improve the health of a person considerably. Here are a few ways you can work on your sleep quality as well –
- Go to bed on time: this sounds quite simple and rather obvious, but over 50% cases of sleep deprivation arise due to insufficient resting time imposed by the person. Stop working on your mobile phone or laptop, reduce exposure to blue light and hit your bed at least 8 hours before the alarm goes off. Establishing a bedtime routine is crucial for sending the correct shut-down signals to your body and mind. Always accommodate at least 60 minutes of sleep time in your sleep schedule. Since REM cycles occur every 60 to 90 minutes, extending your sleep by another hour increases your chances of catching another REM.
- Get yourself checked by a professional: people often experience unwanted awakenings at night due to bladder problems, breathing problems or even indigestion or flatulence. They seem like trivial irritations, but the bear a severe impact on your health. Recurring health problems like these can cause you to lose precious resting time. Several tests like the polysomnography and EEG can help you understand if you have sleep apnea that can be interfering with the quality and quantity of your sleep.
- Avoid caffeine: caffeine seems like the most harmless and the tastiest beverage there is in the world. Something so delicious can never be wrong for our health, or can it be? Coffee can drive away sleep successfully. We should not be drinking more than 100 grams of coffee per day. The active compound does not leave our body immediately, and it is a potent diuretic. Therefore, we lose water content, and that increases the resultant concentration of caffeine in our bodies at the end of the day. Be very careful about your prized macchiato today evening! Drinking coffee too late can impede sleep onset and mess with the beginning of REM sleep.
- Say “no” to alcohol: Alcohol and sleep have been frenemies for a long time. Drinking a lot of alcohol before bedtime can hasten the sleep onset. However, it also reduces the duration of sleep, so you miss out on your regular share of REM cycles. You wake up distraught, without enough restorative sleep behind you. To stay away from this problem, always keep alcohol at least 2 hours away from the bed and drink plenty of water in the meantime to make up for the nasty dehydration.
- Start napping: as an adult, napping is a privilege. Your doctor or your sleep specialist asks you to nap; you merely take the offer! An hour-long nap can fit in a REM cycle, and it can make up for whatever dream action you are missing out at night.
While you are fast asleep, your brain is working non-stop to screen some of the most amazing, sweet, strange, outrageous and, sometimes, scary dreams to you. While you are happily watching the movies in your sleep, your brain is undergoing a massive repair and restoration overhaul. Your central nervous system, autonomous nervous system, and immune system are all undergoing necessary maintenance as well. That is the only reason we feel fresh, energized and ready for the next day.
It’s time for the sweet dreams
Even after knowing so much people ask “what are dreams,” “what are dreams made of,” “what are our dreams telling us.” The answers to these questions are still unreachable due to the human limitations. The brain is a complex organ that not only controls the function of each organ system in our body, but it also controls its functions precisely. It takes care of your memories, and at the same time, it makes sure that you do that math correctly on your test. It is a super organ that neuroscientists are still trying to get to know accurately.
We can confidently say that since the 1950s, there have been several groundbreaking studies on the properties of sleep stages and REM sleep was always on the center stage. The brain goes through 5 stages during regular rest, and these stages consist of 4 NREM and 1 REM stage. A person can only enter his or her REM stage after progressing through the 4 NREM stages. Each step is successively longer in duration than the last one. Finally, the REM stage opens the doors to the dreams. 8 hours of sleep should give you about 4 -5 REM cycles. The fifth REM cycle is the longest of them all. It can last for up to 90 minutes at times. That might be a reason we put a lot of emphasis on our morning dreams. REM sleep is a lot of statistics, physiology, brainwave study, and psychological study, but it is still a mystery to almost everyone.