Sleep
sleep
/slēp/
noun
1. a condition of body and mind that typically recurs for several hours every night, in which the nervous system is relatively inactive, the eyes closed, the postural muscles relaxed, and consciousness practically suspended.
What is Sleep?
Sleep is an important part of our daily routine that accounts for about one-third of our life. Not only is it essential for survival, but it is also a foundational pillar in our health. We often put sleep behind other pillars like nutrition, fitness, and mental health. However, in reality sleep is the foundation on which nutrition, fitness, and mental health sit, as it is a necessity for optimizing health. Good quality sleep contributes to proper organ function, sufficient energy levels, mood stabilization, hormone balance, metabolism, immune function, disease resistance, and much more. Since sleep directly restores almost every system in our body, it is even more important to understand how sleep works and how we can improve sleep quality to optimize our health.
Sleep is a process that is associated with a variety of brain regions. One region associated with sleep is the hypothalamus, a structure part of the limbic system located deep in the brain. The hypothalamus is involved in maintaining homeostasis through the modulation of many bodily processes. This region modulates sleep and wakefulness through the suprachiasmatic nucleus (SCN), clusters of thousands of cells that receive information about light exposure directly from the eyes and control your behavioral rhythm (NIH, 2019). The SCN in the hypothalamus plays an important role in regulating our circadian rhythm (natural, internal sleep-wake cycle) and therefore our sleep patterns. In addition, the SCN sends signals to another region in the brain called the pineal gland, which increases the production of the sleep hormone melatonin, when light decreases. The brain stem is another brain region associated with sleep, that is located in the hindbrain and contains the pons, medulla oblongata, and the midbrain. The brain stem is involved with autonomic functions including the regulation of our sleep-wake cycle. Cells in the hypothalamus and brain stem work together to produce an inhibitory neurotransmitter called GABA. GABA acts as a neuromodulator that reduces activity in the arousal centers of the brain promoting sleep. The thalamus is a brain region associated with sleep that plays a role in forming our dreams. The thalamus is part of the limbic system, and is involved in relaying sensory information to the cerebral cortex. During rapid eye movement (REM) sleep, the thalamus becomes active and sends our cortex sensory stimuli that appear as our dreams.
Sleep is also a process that occurs in stages that are split into two basic types, rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. There is one stage of REM sleep and three stages of NREM sleep, and each stage is linked to specific patterns of brain activity. In a
full night of sleep, we pass through each stage about 4 or 5 times with REM stages increasingly getting deeper and longer throughout the night. The first stage of sleep (NREM-1), is the transition from wakefulness to sleep. In this stage, bodily processes including brain activity begin to slow. The second stage of sleep (NREM-2), is a light stage of sleep before deep sleep, where bodily processes slow even more and body temperature drops. We spend most of our repeated sleep cycles in this stage. The third stage of sleep (NREM-3), is deep sleep and this is where bodily processes are at their slowest. Deep sleep occurs for longer periods of time and is what helps our body recover and feel rested. The other stage of sleep is REM sleep, and this is when our eyes rapidly move from side to side while our eyelids are closed. During REM sleep, our heartrate, breathing, and brain activity increase to similar levels seen in wakefulness and most of our dreaming occurs during this stage.
As important as sleep is for our overall health, a third of US adults report that they usually get less than the recommended amount of sleep (CDC, 2020). Lack of sleep is associated with poor organ function, energy levels, mood, hormone balance, metabolism, and immune function. In addition, chronic sleep deprivation is associated with an increased risk for disease and negative long-term brain effects. Our brains get rid of waste through the glymphatic system when we sleep, allowing us to remove toxins that build up throughout the day. Research suggests that these toxins build up excessively when we are sleep deprived, increasing the risk for common age-related neurological disorders like Alzheimer's disease and Parkinson's disease (NIH, 2019).
There are many ways to improve sleep quality to improve our overall health. The National Sleep Foundation Guidelines recommend that adults get an average of 7-9 hours of sleep a night, and recommend that children get an average of 10+ hours of sleep a night for growth and development (NSFG, 2021). Ways to improve sleep hygiene include having a set sleep schedule by sleeping at the same time everyday, creating a sleep environment by avoiding bright light and reducing room temperature, avoiding caffeine, nicotine, and alcohol before bedtime, and exercising during the day to increase the amount of time spent in deep restorative sleep.
"Human beings are the only species that deliberately deprive themselves of sleep for no apparent gain."
