Why Do We Need Restful Sleep?

Does this look familiar to you?

The act of sleep is actually quite complex and involves two basic types of sleep: rapid eye movement sleep (REM) and non-REM (NREM) sleep. NREM is the most restorative type of sleep, so the amount you need increases when you’re sleep deprived.^[1] REM sleep, on the other hand, involves increased brain activity and is when dreaming occurs. NREM sleep has 3 different stages of depth of sleep and alternates with REM sleep throughout the night.^[2]

Generally when people are woken up from REM sleep, they remember their dreams and describe them as vivid and sometimes crazy dreams. Typically when awakened from NREM sleep, dreams are harder to recall. Also, during REM sleep our muscles in our arms and legs are temporarily paralyzed to prevent us from “acting out” our dreams. (Except for dogs that run in their sleep!) That being said, have you ever been jerked awake by a sensation of falling, just as you were drifting off to sleep? These are called myoclonus jerks, and are an involuntary contraction and relaxation of the muscles which causes jumping or twitching during the transitional period between wakefulness and sleep.^[3]Interestingly, sleepwalking, sleeptalking, and sleep terrors occur during NREM sleep, usually in the deep sleep stage.^[4]

Further, our sleep cycle is determined by our innate 24-hour body clock known as a circadian rhythm.^[5] This internal clock is affected by the amount of light your body receives in response to darkness. Our body produces hormones such as melatonin which triggers sleep, and in the morning, sunlight stimulates wakefulness. We know that these circadian rhythms can be disrupted by not only stress, but things like jetlag and shift work^[6].

Have you ever found solutions to one of your problems after sleeping on it? Or woken up in the middle of the night with inspiration from a dream? It seems that it has something to do with memory reshuffling especially during REM sleep that allows for integrating previously encountered information in order to solve problems creatively.^[7] Restful sleep is necessary for not only memory consolidation, but rejuvenation of our mood, enhancing chemicals and hormones that are necessary for our physical maintenance, immune functioning, and learning.^{[8] [9]} Good, restorative sleep can also help reduce physical pain.^[10]

Our bodies regulate our sleep much in the same way that it regulates eating or drinking. When our body needs nourishment, we get hungry. When our body needs rest, we get tired. Every individual is unique and requires somewhat of a different amount of sleep to function at their best. What is important is that the amount of sleep that you get should be sufficient for you, and that you usually feel refreshed when you wake up and not sleepy during the daytime.

In general, according to the Center for Disease Control (CDC), “short sleep duration” for adults is defined as less than 7 hours per day hours per day, and on average approximately 35% of adults describe issues with poor sleep or insomnia.^[11]Difficulty sleeping can mean not being able to fall asleep, waking up too early, lying awake for long periods in the middle of the night or not feeling refreshed after a night’s sleep.

While insomnia is often a temporary issue in response to stress, life problems, jet lag, or a change of routine, persistent loss of sleep can severely affect one’s well-being. Chronic insomnia has serious health ramifications due to the disruption in the body’s rest and repair cycle.^[13] Chronic insomnia can cause an assortment of medical, psychological, and social disturbances such as daytime fatigue, poor concentration, loss of drive to do things, irritability, depression and anxiety, as well as potential for increased incidence of disorders such as obesity, cardiovascular disease and Type 2 Diabetes.^[14] This can affect the ability to work, social activities and overall well-being.

Getting a proper sleep not only impacts our daily life, but it is also increasingly being recognized as an important piece of the stress-immunity puzzle. We’ve all heard the adage that when we’re sick with a cold or flu, we need lots of rest. This is not just an old-wives tale, it is actually based upon science. When we sleep, our body releases the cytokines that protect us from inflammation and infection.^[15] Without proper sleep we will not produce enough cytokines and have a harder time fighting off viral and bacterial illnesses.^[16]  One study found that two nights of total sleep deprivation increased the numbers of circulating leukocytes and decreased lymphocyte and neutrophil function in healthy male volunteers.^[17] Recall that leukocytes are an important cellular marker of systemic inflammation, and neutrophils are important in fighting infection.

Another interesting study used identical twins as participants to compare their sleep and immune system functioning. Researchers looked at the twins’ different sleep patterns – one sleeping longer and better than the other – in relation to their immune systems. Poorer sleep was shown to be associated with depressed immune responses to infections and thus adverse metabolic, cardiovascular, and inflammatory outcomes.^[18]

So of course, our ‘evil villain’ chronic stress affects our sleep by dysregulating the sleep-wake cycle. Cortisol levels usually decrease at night to help us sleep; however, studies have found that people with insomnia have higher levels of cortisol in the evening which causes an increased number of nighttime awakenings.^[19]

If you consider some of the side effects of stress, it clearly illustrates how we can have a hard time sleeping. Muscle tension occurs when we’re stressed, and this can hinder the relaxation needed for peaceful sleep. When we’re stressed we have an elevated heart rate and rapid breathing; however, sound sleep requires the opposite as during REM sleep our heart rate and breathing slows down.^[21]Stress also affects our digestive system causing us to experience abdominal pain, diarrhea or constipation, annoying us when we’re trying to sleep. So of course, not getting enough sleep has a reciprocal impact on our stress levels and mood, compounding the problem.

A few more factors that can impair one’s sleep are medical problems such as cardiac or pulmonary issues, pain syndromes such as fibromyalgia or arthritis, or snoring and obstructive sleep apnea. People with sleep apnea have pauses in breathing for 10 to 20 seconds or more when they sleep due to their throat muscles relaxing and narrowing their airway. Many don’t even know how often they stop breathing during the night, even when they briefly wake up choking or snorting. This process lowers the oxygen level in their blood and raises their risk of heart attacks and stroke. Oftentimes someone with sleep apnea feels unrefreshed when they wake up and are very sleepy during the daytime.^[22]

Here is a 2 minute “Central Sleep Apnea Unmet Need Video” showing someone’s apneic spells and their oxygen desaturations! In general for most people, oxygen saturation levels should be 95% and higher.