Sleep Overview: The Benefits of Sleep

Introduction to Sleep

Do you know that the amount of sleep you get has a lot of influence on your wellbeing? Getting a good night's rest is possible by sticking to simple and consistent healthy behaviours, such as maintaining sleep hygiene, avoiding caffeine and alcohol at night, and adhering to a regular sleep schedule. Understanding factors that influence sleep could help improve your sleep quality. This article explains why we need to sleep, how to have a good night's rest, sleep disorders, and the effect of sleep deprivation on our health. 

Sleep Stages

Sleep is the behavioural and physiological changes that occur to the body and brain whilst a person is sleeping.¹ The behavioural changes observed when a person is said to be asleep could include limited or lack of body movement, decreased response to the immediate environment and lower brain activity.¹ 

There are two main categories of sleep: rapid eye movement sleep (REM) and non-rapid eye movement sleep (non-REM).¹ Non-REM sleep is subdivided into three stages of sleep, whilst REM sleep is categorised as the fourth stage of sleep. Figure 1 illustrates the process involved in sleeping. During a normal eight hours of rest, there is a cyclic change between non-REM and REM sleep, and this cycle usually occurs at least five times.⁶

Stage 1

This is an intermediate stage between being asleep and awake, and it is characterised by slow eye movement. As breathing and heartbeat rate slows down, the muscles relax as well.¹⁶  Stage 1 of the sleep cycle is the lightest phase of sleep and generally lasts about seven minutes.¹⁶

Stage 2

This stage accounts for about 50% of the total sleep duration and during which ‘sleep spindles’ (short releases of electrical activity in the brain) occur. Breathing and heartbeat rate continue to reduce at this stage, as well as body temperature. Stage 2 can last for 25 minutes.^16,6

Stage 3

This stage, also known as slow wave sleep,  is a very important part of sleep because its quality determines how refreshed you will feel when you wake up.¹⁶ At this stage, the sleeper enters into a very deep sleep; during deep sleep, the body repairs worn out tissue and muscles, both which are beneficial for growth and development. Additionally, it improves immune function. This stage accounts for about 20% of the total sleep duration.

Stage 4  

This stage is known as REM sleep; it accounts for about 25% of the total sleep duration and is characterised by rapid eye movement (the eyeballs roll quickly) and complete loss of muscle movement.¹⁶ This is to prevent you from acting out your dreams in reality, as this is the stage in which a sleeper dreams. During REM sleep, your heartbeat and blood pressure increase and the pace of breathing quickens.^6,15 This sleep stage is crucial to learning processes in humans, concentration during daytime and the overall mood of the sleeper.

Circadian Rhythms that Influence Sleep

As each day passes, most people expereince the natural urge to fall asleep and wake up. Many of us feel the need to sleep when we are stressed out and the urge to wake up when we feel well-rested. The hypothalamus ( a part of the brain) controls this drive to sleep and wake up, and is known as the circadian rhythm.¹ The circadian rhythm helps in regulating sleep and wakefulness. It changes in a cyclic flow every 24 hours.² Your circadian rhythm is controlled by hormones and chemicals in the body. 

Daylight and darkness affect our circadian rhythm: during daylight, the eyes receive lighting and decrease the level of a hormone called “melatonin”, causing the urge to be awake to increase; however, when darkness approaches, the level of melatonin increases, causing drowsiness and creating a drive to sleep.²

How much sleep should you get?

The amount of sleep everyone needs is determined by our age, as well as our health conditions. According to the American Academy of Sleep Medicine, the required daily average sleep for adults is about 7 to 9 hours of sleep,  around 9 to 14 hours for children, and toddlers and babies need between 12 and 16 hours of sleep.

Changes with Age

Changes in sleep pattern and duration occur as newborns grow and later become adults. This is because of the development of the central nervous system. It was observed that infants have a “polyphasic sleep pattern”­, meaning they have multiple periods of sleep in a day, summing up to 16 hours per day. Moreover, the elderly exhibit a ‘biphasic sleep pattern’, such that they sleep twice a day –  at night and for a few hours during the day – summing up to an average time of 8 hours or more per day.

The Importance of Sleep

The importance of sleep cannot be overemphasised; various studies have been carried out to show the relationship between sleep and memory, sleep and mental health, sleep and immune system, etc. This section focuses on the importance of sleep and its effect on human wellbeing.

1. Increased concentration and productivity

In a national survey carried out among American adults in 2008, findings showed the effect of sleep on the concentration and productivity of employed respondents of the poll.⁹ About 29% of the respondents experienced sleepiness at work due to sleep deprivation or sleep disorders. This in turn, resulted in reduced concentration and productivity at work. Alternatively, alertness and wakefulness increased attention to detail, sharpened concentration and increased productivity.⁹

2. Improved Memory

Memory functions consist of three processes: encoding, consolidation, and retrieval. The formation of new memory traces occurs after receiving information during encoding. The consolidation process helps in strengthening the new information, while the retrieval process is the point at which you recall the information stored. Studies have found that sleep plays a major role in memory consolidation.⁴

Encoding and retrieval take place during wakefulness, whereas memory consolidation occurs during sleep. Although there is no direct understanding of how sleep helps in memory consolidation, it is believed that the brain waves that occur at the various sleep stages aid in consolidating memory.¹⁷

3. Cardiovascular Health

Studies have found that cases of coronary artery disease increased in the population of people who sleep for less than 6 hours per night. It was also established that the risk of dying due to cardiovascular diseases is increased among elderly people with poor sleep quality and that the incidence of this was very low among those that sleep for 7-8 hours per night. Therefore, strong evidence suggest that sleep plays an important role in improving your cardiovascular system.⁸

4. Blood Sugar and Diabetes

A recent study published in Diabetologia (the journal of the European Association for the Study of Diabetes) found that there is a direct effect of sleep quality on various chronic health conditions such as cardiovascular disease, obesity, and type-2-diabetics. It also suggested that good sleep affects the ability of the body to regulate glucose levels11 However, according to WebMD, people who sleep for more than 9 hours are at higher risk of developing diabetes.¹⁸

5. BMI

Body Mass Index (BMI) is calculated using two measurements, weight and height. Your BMI value shows whether you are underweight, overweight, or obese. The 2008 Sleep in America poll findings shows that 75% of the obese respondents had less than 6 hours of sleep on workdays. Another study revealed that BMI increases with lower sleep duration and decreases with increased sleep duration.¹⁰

6. Boosts Immune System 

An increased amount of sleep during an infection or sickness is presumed to help improve the immune system and enhance the body’s defence. Good quality sleep has a positive influence on immunity, and this is suggested by improved vaccination responses and infection outcomes.³

7. Mental Health

Sleep affects your mental health because sleep deprivation influences your cognitive thinking. An impaired cognition may lead to poor choices and an inability to think things through before acting. Additionally, poor quality sleep can be a risk factor for depression.⁷

Sleep Deprivation

Adults that sleep less than 7 hours a day are experiencing sleep deprivation. Short-duration sleepers are at higher risk of ill-health. Sleep deprivation and lack of sleep can affect your overall health and make you prone to chronic health conditions, such as diabetes, heart disease, high blood pressure, and obesity.

Effects of Chronic Sleep Deprivation

Chronic sleep deprivation (CSD) can affect an individual’s cognition, thereby affecting their ability to acquire knowledge and form and recall memories. CSD also affects mood and can increase anxiety. Other effects of CSD may include altered circadian rhythm, emotional dysregulation, increased level of impulsivity-acting on impulse, as well as suicidal behaviour.¹⁴

Symptoms of Deprivation

The following include some of the symptoms of sleep deprivation: 

• Weakness & Fatigue
• Severe Mood Swings
• Memory Problems
• Increased Risk For Insomnia
• Hallucinations
• Drowsiness

Tips for getting a good night's sleep

Having a good night's sleep can not be overlooked, considering the importance of sleep to your health and general well-being. The following are helpful tips for achieving this.

Stick to a regular sleep schedule

In the 2019 Sleep in America Poll, a strong relationship was established between a consistent sleep schedule and good night's sleep. It demonstrated that maintaining a consistent sleep schedule will improve your sleep quality.¹⁹

Avoid caffeine and alcohol late in the day

Reducing the amount of alcohol you consume before sleeping can considerably limit sleep disruptions.²⁰ Alcohol is a sedative, and whilst it may aid with sleep in the short term, it disturbs the balance of the sleep stages. An excess of alcohol before sleep allows the body to fall into a night of deep sleep quicker than normal. Consequently, there is an imbalance between slow-wave and REM sleep which causes sleep disturbances and reduces the overall quality of sleep.²⁰ The Sleep Foundation advises that you should stop drinking alcohol at least four hours before sleep to avoid sleep disturbances.²⁰

Implement 'sleep hygiene'

Cultivating healthy sleep habits that enhance your ability to quickly fall asleep and stay asleep longer is referred to as sleep hygiene. These habits can include sticking to a consistent sleep schedule, avoiding drinking alcohol and caffeine 3 to 4 hours before bedtime, and avoiding heavy meals at nighttime.^{12, 13}

Limit blue light exposure before bed

Reducing your exposure to light before bedtime will help increase your sleep drive and consequently affect your circadian rhythm, also known as your natural body clock. Blue light lowers the production of melatonin, and this increases the urge to stay awake.¹² Electronic devices such as cell phones produce blue light; therefore, using your cell phone at bedtime is likely to increase the time it takes you to fall asleep.¹²

Sleep Disorders

A person who consistently experiences poor quality sleep is at a higher risk of developing sleep disorders. These conditions can include sleep apnea, insomnia, narcolepsy and restless legs syndrome. This article will further provide details for the first two:

1. Obstructive Sleep Apnoea (OSA)

A person who suffers from OSA often experience the following symptoms while sleeping:

• Severe sleep disruption
• Loud snoring
• Choking
• Excessive sweating at night
• Heartburn

Daytime symptoms can include: 

• Incessant headache in the morning
• Hyper Activeness
• Hearing Loss
• Forgetfulness
• Dryness of mouth when waking up in the morning 

OSA can be caused by obesity, ageing in adults, smoking, drinking alcohol, lying on the back as a sleeping posture, and even having large tonsils can increase the risk of developing this condition.

Effect of untreated OSA

Effects could include the following: 

• High blood pressure
• Low concentration during the daytime
• Mood swings
• Tiredness

How to Treat OSA

There are various treatments for OSA; they are dependent on the severity of your condition. One such example is continuous positive airway pressure (CPAP) machines. They work by pumping air gently into a mask that you have to wear while asleep. These machines are often effective when used consistently. ²¹

Another treatment option is a surgical operation in which large tonsils are removed to aid breathing.²¹

2. Insomnia

This sleep disorder occurs when a person finds it difficult to fall asleep and stay asleep. You are at risk of having insomnia if you experience the following conditions:

• Depression
• Noise in your sleeping area
• Uncomfortable bedroom temperature
• Consumption of caffeine
• Jet lag

Maintaining good sleep hygiene can help prevent insomnia. Treatment of insomnia varies depending on the cause of the disorder and can involve being referred to a therapist or even having to take sleeping pills for a short period of time.⁵

Summary

Ultimately, good quality sleep has a significant long- and short-term effect on your health and wellbeing. Consistently not getting a good night’s rest or long-term sleep deprivation and sleep disorders could warrant a visit to the doctor.