Nearly every tissue in the human body contains specific proteins that keep track of day and night, seasonal changes and aging. These proteins build up in our body’s cells when the sun is out, activating wakefulness and alertness, and lessen during darkness, activating restfulness and promoting sleep. This is how we develop a sense of internal timing, referred to as a biological clock (NIHGMS, 2022). 

These timing proteins take their cues from our master clock, which is a series of around 20,000 neurons in the brain that refine the information brought in by our senses. This information is then used by the body to influence our physical and mental processes, as well as our behavior, forming our own personal circadian rhythm (NIHGMS, 2022). 

What happens to our bodies during sleep is not entirely understood, however, we do know that we undergo physical changes that allow us to psychologically disengage from environmental perception and response (Potter, 2020). Sleep can also help restore hormonal balances, enhance protein synthesis and encourage internal repair. When we rest, our digestive system, heart and lungs each go through natural rhythms that help improve our overall function during the day (NINDS, 2021). 

Our time spent sleeping is separated into two distinct phases, rapid eye movement (REM) and non-rapid eye movement (NREM) (Weiner, 2010). 

REM sleep is sometimes called paradoxical sleep, because our brain activity is in some ways similar to being awake. In this phase, our brain waves are low voltage and high frequency and our muscles are paralyzed except those that help us breathe and those that move our eyes. Our blood pressure, heart rate and respirations are highly variable and our brain metabolism is normal or slightly above normal. We most often dream during REM, and if awoken in this phase, between 70% and 80% of us will be able to describe our dream content (Weiner, 2010).

NREM sleep is divided into four stages. Stage one is our transition into sleep from wakefulness, and each stage after is progressively deeper than the last. During NREM, brain waves are high voltage and low frequency and our brain metabolism is lower than normal. We do not experience muscle paralysis, nor do our eyes move rapidly while in this phase. Dreaming can occur in NREM for about 30% of us, and it is during NREM sleep that sleepwalking and night terrors occur (Weiner, 2010).

In terms of evolution, NREM sleep is thought to have developed before REM due to its influences on our more basic processes. The primary role of NREM is believed to relate to the conservation and restoration of our body’s metabolic energy, as well as the restoration of our ability to function cognitively. REM sleep is utilized for higher level mental functioning, memory processing, and the growth and development of our nervous system (Weiner, 2010).

We move through the two phases of sleep in a cycle that repeats itself approximately every 90 minutes, usually between 3 to 5 times each night. With each successive phase repetition, the relative amount of time spent in REM increases. It is estimated that about 25% of time spent by adults sleeping is spent in REM, with this number decreasing as we age (NINDS, 2021).

Each of us has a unique sleep cycle, which can vary night to night depending on the activities of the day (Weiner, 2010). For those between the ages of 18 and 64, the amount of sleep needed per night ranges between 7 to 11 hours. Sleep quality is considered to be high if we wake up feeling alert or energetic, and our sense of quality is highly dependent on the number of hours spent asleep (NINDS, 2021).

In the United States, more than 42% of adults report getting less than 7 hours of sleep on average. Meaning many of us operate daily in a state of sleep deprivation (Potter, 2020). The most common indication that we are sleep deprived is the feeling of dozing off (USDHHS, 2022) or general fatigue (NINDS, 2021). 

Impact of Sleep on Mental Health

Mental health and quality of sleep are closely correlated. The less sleep we get, the less able we are to cognitively function (Potter, 2020). 

When tired, it is more difficult to accurately interpret the words and actions of other people, and we may struggle to manage our behavior and emotions. We can become more easily frustrated, irritable or anxious in social environments, and overreact or under-react to events that occur (USDHHS, 2022). 

Without adequate sleep, our learning capacity, ability to focus, and problem solving skills start to diminish. Our coping mechanisms and memory can become harder to access. We tend to take longer to finish tasks, make more mistakes and engage in more risky behavior (USDHHS, 2022). Because of these changes, our decision making ability is significantly impaired (NINDS, 2021).

Those experiencing depression and anxiety often encounter sleep disruptions that manifest as fragmented sleep or excessive sleep (Potter, 2020). With depression specifically, changes in our sleep patterns are similar to those that occur with aging (Weiner, 2010).

Impact of Sleep on Physical Health

When sleep deprived, the hungry hormone (ghrelin) and the full hormone (leptin) don't have the time they need to self regulate. This leads us to have extra hungry hormones during the day, so we eat more than we would have if we had been well rested. Our bodies also become less sensitive to the insulin hormone that controls blood sugar, meaning our blood sugar goes up and fluctuates more during the day (USDHHS, 2022). 

Deep, restful sleep releases growth hormones that influence puberty and fertility throughout our life cycle. These hormones enhance our ability to grow muscle mass and repair our body’s cells and tissues. Those who are sleep deficient can experience a weakened immune system and are at a higher risk of getting an infection. Poor sleep makes it more difficult to fight off infection, and also increases the risk of chronic illnesses like high blood pressure, kidney disease, diabetes, obesity, heart disease and stroke (USDHHS, 2022).

Sleep deficiency has been shown to impact cognitive function in a similar manner to being drunk. This condition is responsible for well over 1,500 crash deaths each year, industrial hazards resulting in loss of life and limb, and in-home accidents that lead to falls, injury and broken bones (USDHHS, 2022).

When we are lacking in sleep, our body may elect to create sleep conditions while we are awake through a process called microsleeping. This presents as an uncontrollable loss of cognitive function while we are technically awake, and it is marked by a loss of short term memory. A common example is driving long distances, and upon arrival to our destination, realizing we can’t recall a significant portion of travel time (USDHHS, 2022).

Roadblocks to Sleep

Napping has been researched thoroughly, and despite its appeal to those who are sleep deprived, daytime sleeping often does more harm than good. Napping makes it more difficult to fall asleep and stay asleep during the night, which prolongs the cycle of sleep loss and increases reliance on napping in the future (Potter, 2020).  

Another culprit behind poor sleep quality is the use of technology in bed. Televisions, phones and computers all provide a bright source of light and prolonged distraction that makes it harder to fall asleep and maintain sleep. As do certain medications, late night eating and stress (Potter, 2020).

Unsurprisingly, working the swing shift or night shift can drastically alter our sleeping habits and negatively influence our ability to fully rest (Potter, 2020).

Strategies to Improve Sleep

Improving our quantity and quality of sleep begins with initiating good sleep habits. We can start by increasing our level of tiredness throughout the day so that we are naturally able to fall asleep faster and sleep more deeply. Staying awake for longer periods of time is one option (waking up early and skipping a nap for example), and engaging in physicality is another (Potter, 2020). For examples of ways to move throughout the day, click here.

Good sleep habits have been compiled into a dos and don'ts list, commonly referred to as sleep hygiene. The goal of this list is to facilitate sleep quality and encourage wakefulness during the day. Now, let's explore the list below for strategies that can improve our sleep experience (NINDS, 2021):

  • Pay attention to our circadian rhythm.
    • Are we an early riser or a night owl?
    • What time of day do we feel most awake? Most tired?
    • What steps can we take to honor our biological need for sleep?
  • Try to set a consistent time to begin our sleep routine.
    • Set an alarm for the same time each morning.
    • Allow ourselves at least 7 hours of sleep by timing our efforts to fall asleep.
  • Engage in calming bedtime rituals that we only do prior to falling asleep.
    • Drink a warm, caffeine free beverage.
    • Wash our hands and face.
    • Use the bathroom.
    • Take a bath.
    • Read a book.
    • Listen to soothing music.
    • Consider meditation or prayer.
  • Create a comfortable sleep space and atmosphere.
    • Make an effort to ensure our sleep space is welcoming.
    • Ensure linens are clean, dry and have a texture that feels good on our skin.
    • Select a cooler or warmer ambient temperature depending on preference.
    • Ensure proper movement of air through the sleep space.
  • Eliminate distractions.
    • Dim the lights while preparing for bed.
    • Turn lights off when sleeping.
    • Turn off the radio or television.
    • Do not use phones or laptops in bed.
  • Wear loose fitting, comfortable clothing to bed.
  • Support joints with pillows.
    • Use pillows to prop up into a comfortable position.
  • Use the bed exclusively for sleeping or sexual activity
  • Exercise in the morning or afternoon.
    • Avoid exercising at night as this can increase energy levels late in the day.
  • Avoid studying, working or dealing with problems within the family prior to bed.
    • Hold off difficult tasks until the morning.
  • Avoid napping if possible.
  • Avoid heavy meals, caffeine, alcohol and nicotine in the hours prior to sleep.