How does sleep affect the lives of individuals?

By: Sharanya

Edited: Ritisha Debnath

Sleep is a fundamental process that occurs at cellular, physiological, and behavioral levels in the human body. Similar to eating food, drinking water, keeping your body mentally and physically fit, sleep is vital to the human body for numerous reasons.  At the basic level, sleeping allows for energy conservation, self-repair/recovery of the body and memory consolidation. Although during sleep the body seems to be at rest, the brain is actually still performing activities. Sleep occurs through the interaction between two systems: circadian rhythm and homeostasis. 

During the day,  when awake, the brain releases adenosine, a chemical that accumulates throughout the day increasing the pressure to sleep. Additionally, the SCN (suprachiasmatic nucleus) located in the hypothalamus detects light via the eyes making the call to trigger the pineal gland to release melatonin to promote sleep when it is dark. In turn, when there is light, the levels of melatonin decrease in order to keep you awake. Sleep promoting cells in the hypothalamus and brainstem release GABA, a brain chemical that reduces activity in those areas of the brain and relaxes the muscles. Furthermore, the transition into waking up also depends on the hormone cortisol which increases alertness throughout the day and it counteracts the hormones adenosine and melatonin in the morning.

There are primarily two sleep stages, the rapid eye movement (REM) stage and non-REM sleep stage. Humans usually go through four to six sleep cycles per night with each cycle lasting from ninety to one hundred and twenty minutes. Stage one of non-REM sleep is the transition from wake to sleep– a period of relatively light sleep where the heartbeat, breathing, eye movements, and the brain start to slow down from their usual trends. The muscles in your body start to relax and this lasts for a brief period of time. Next, in stage two of non-REM sleep is the period where you enter even further into the deep sleep, similar to the first stage the same functions occur but at even deep levels. Your body temperature will drop, eye movements completely stop, and brain wave activity slows but brief bursts of electrical activity occur, producing specific patterns. This stage is where you will spend most time out of all the stages. Followed by this stage is stage 3, “a period of deep sleep…occurs in longer periods during the first half of the night” (Brain Basics: Understanding Sleep). At this point, heartbeat, breathing, and brain waves are at their lowest levels and the muscles are relaxed to where it is difficult for you to wake up. This stage is crucial for the “consolidation of non declarative memories”( Differential Effects of Non-REM and REM Sleep on Memory Consolidation) or facts and events. Lastly, the REM stage “first occurs about 90 minutes after falling asleep…[is when the] eyes move rapidly from side to side behind closed eyelids” (Brain Basics: Understanding Sleep). Breathing becomes faster and irregular in this stage, and the  heart rate and blood pressure increase. Dreams primarily occur in this stage and REM sleep is crucial for “non declarative memories” (Differential Effects of Non-REM and REM Sleep on Memory Consolidation) otherwise known as consolidating emotional and procedural memories like motor skills. 

The recommended amount of sleep needed is  as follows: newborns (birth to 3 months) need between 14-17 hours, infants (4 months to 12 months) need between 12 -16 hours including naptime, young children (ages 1 to 5) need between 10 to 14 hours including naptime, school aged children (ages 6 to 12) need 9-12 hours, teenagers (ages 13 to 18) need 8-10 hours and adults (18 and older) need 7-9 hours. Although these are the recommended and usual amounts that people sleep, these aren’t concrete sleeping  amounts, thus individual needs is what defines your sleep amount. Factors like genetics, age and lifestyle all contribute to the hours of rest a specific person needs. 

Sleep disorders are conditions that disrupt sleep patterns which reduce optimal function and wellbeing of the body. Narcolepsy is a condition of overwhelming sleepiness during the day, these sudden “sleep attacks” occur because the brain is unable to regulate your sleep wake cycle.  This condition can include two different types: Narcolepsy Type 1 and Narcolepsy Type 2 where type 1 causes “sudden muscle weakness and/or very low levels of a brain chemical called hypocretin/orexin” and type 2 “causes daytime sleepiness like type 1, but without cataplexy” (Cleveland Clinic Narcolepsy). Symptoms of this, in addition to the ones mentioned above, are: hallucinations, sleep paralysis, and poor nighttime sleep. Circadian rhythm disorders occur when your body’s internal sleep wake cycle falls out of sync with the environment. This includes conditions like jet lag disorder, shift work sleep disorder (SWSD), delayed sleep-wake phase disorder (DSWPD), advanced sleep-wake phase disorder (ASWPD) and many more. Insomnia is a sleep disorder that makes it difficult for someone to fall asleep or stay asleep which includes symptoms like memory issues, trouble falling asleep, waking up too early without being able to fall back asleep etc. Parasomnia is a sleep disorder that causes abnormal experiences or behaviors during sleep, split into non-REM, REM and other parasomnias. Non-REM parasomnias includes: sleep terrors, sleepwalking , confusional arousals; REM parasomnias includes: nightmare disorder, RBSD, recurrent isolated sleep paralysis; and others include: bedwetting, sleep related groaning, and sleep related hallucinations. Sleep apnea is a condition that makes you stop breathing due to a blockage in airways or because the brain doesn’t control breathing as usual. The three types are obstructive sleep apnea (OSA), central sleep apnea (CSA) and mixed/complex sleep apnea or a mixture of both obstructive and central sleep apnea. Lastly, there are sleep-related movement disorders, such as restless leg syndrome, which don’t have  cures, but there are treatments.

Additionally, “some people with damage to the SCN sleep erratically throughout the day because they are not able to match their sleep/wake cycle (circadian rhythms) with the light-dark cycle. Most blind people maintain some ability to sense light to help them regulate their sleep/wake cycle” (Brain Basics: Understanding Sleep).

In the long run, many sleep disorders/conditions can be prevented through lifestyle and sleep routine changes. Avoiding excessive amounts of screen time at late hours, caffeine and alcohol are red flags to watch out for. In the end, if you notice sleep problems consistently, it is best to contact your PCP and look into sleep specialists if needed.