Sleep

SUMMARY

• Sleep is a natural and complex process that decreases the sensory activity of the human body.
• There are two types of sleep including rapid eye movement sleep and non-rapid eye movement sleep.
• Good quality sleep is important for developing long term memory.
• Genes have an important impact on sleeping patterns and related diseases. 
• Sleep deprivation negatively affects the mental and physical health of a person. There are various sleep-related diseases including insomnia, sleep apnea and REMS behavior disorder.
• Sleep hygiene practices improve the quality of sleep, thereby improving the overall quality of life
• Regulation of sleeping time should be made a priority to ensure healthy living.

WHAT IS SLEEP?

Sleep is a complex and dynamic process that involves a decreased ability to interact with surroundings due to comparatively inhibited sensory activity, decreased activity of muscles and almost no activity of voluntary muscles.

It is a naturally repeated state of body and mind with decreased sensual activity. Quality sleep is essential for survival like food and water (Carley and Farabi, 2016).  

TYPES OF SLEEP

Generally, there are two types of sleep including non-rapid eye movement sleep (NREMS) and rapid eye movement sleep (REMS).  

Non-rapid eye movement sleep (NREMS)

NREMS does not involve eye movements and dreaming is rare in this kind of sleep. People may get stuck in NREMS if they do not go through the sleeping stages properly. Mental activity in NREMS is organized and thought thereby enabling some people to sleepwalk. There are three stages of NREMS:

1. First stage of NREMS is the beginning of sleep that is often called relaxed wakefulness. If a person is aroused from this stage of sleep, he thinks that he has been fully awake. There is slow eye movement in this stage of sleep. People may also experience involuntary jerks called hypnic jerks while transitioning into stage one sleep.
2. Second stage of NREMS is a transition between first stage and deep sleep. In this phase, muscles relax while heartbeat and muscle contraction slows down. Brain activity decreases, eye movements stop and body temperature also decreases.  
3. Third stage of NREMS is also called deep sleep that helps a person to wake up fresh in the morning. Heartbeat, brain waves and breathing rates are at their lowest during this stage of sleep. If a person is awakened from this stage of sleep, he will awake groggy because mental performance is somewhat impaired during the deep sleep. That is why awakening from this stage is difficult and this phenomenon is often called sleep inertia (Carskadon and Dement, 2005). About 40-50% of schizophrenia patients have low levels of third stage NREMS.  

Rapid eye movement sleep (REMS)

REMS involve rapid movement of eyes and low muscle contraction. Heartbeat and blood pressure are close to waking levels. Breathing rate becomes irregular and faster. A person may have vivid dreams during this kind of sleep.

If a person is awakened from REMS, he is more receptive and can perform better on creative problem solving. Interestingly, the low muscle contraction, especially in the legs and arms prevents a person from acting out dreams. Some people can differentiate among colors in dreams while others have black and white dreams.

Chemical and electrical activity controlling this kind of sleep initiates in brain stem and involves presence of acetylcholine and absence of norepinephrine, serotonin and histamine. REMS occurs at around first 90 min after falling asleep. However, REMS time decreases with aging and old people have very brief REMS (Peever and Fuller, 2017).

SLEEP AND MEMORY CONSOLIDATION

REM is related to procedural memory improvement while NREMS is useful for memory consolidation. In other words, both REM and NREM help to reactivate and consolidate memories.

The hippocampus region of the brain has an important role in this process where high frequency oscillations reactivate neuronal activity. Short term memories in hippocampus are redistributed to neocortex region of the brain where they develop into long term memories.

The irrelevant information is removed by synaptic downscaling while rest of synapses is reactivated and potentiated thereby developing memories (Peter-Derex, 2019). 

GENETIC FACTORS RELATED TO SLEEP

Genes play a significant role in sleep and various genes have been found that control the sleep-wake cycle, excitability of neurons and timing of sleep. Some of the genes in cerebral cortex of the brain have variable expression between sleep and wake states.

Due to variable expression of a sleep-linked gene, ADRB1, some people may need to sleep less than others. In a recent study, various new gene regions have been found related to duration of sleep.

Therefore, the tendency for developing insomnia and other sleep related diseases can be predicted with genome wide screening of patients. Additionally, these genes may be targeted to develop a cure from sleep related illnesses (Lane et al. 2017).          

EFFECTS OF SLEEP DEPRIVATION

Sleep deprived people need an alarm clock to wake up in the morning and it is very difficult for them to get out of bed in the morning. Sleep deprived people get drowsy while driving or after meals.

They may also fall asleep while watching TV or reading books. On a broader spectrum, sleep deprived people are fatigued, depressed and lack motivation. They face problems with memorizing, concentrating, problem solving and decision making. Sleep deprivation weakens immune system that increases the chances of infections.

Effects on heart and brain functioning leads to diseases like Alzheimer’s, high blood pressure, diabetes etc. Sleep deprived people also have increased perception of pain (Bandyopadhyay and Sigua, 2019). 

DISEASES RELATED TO SLEEP

The normal sleep process may be disturbed in some people leading to trouble in normal sleeping and various sleep disorders. 

Insomnia

Insomnia is a common sleep disorder in which the patient finds it difficult to fall asleep or stay asleep. Patients may wake up early in the morning and feel tired upon waking.

Insomnia can be short term (acute insomnia) that lasts from 1 night to a few weeks or long term (chronic insomnia) that lasts from 3 nights a week for 3 months or longer. It is caused by stress, anxiety, inappropriate environmental factors like extreme temperatures or other diseases like allergies, asthma etc.

Sleeping pills for treating insomnia may have negative effects. Therefore, insomnia should be treated by treating the causative factors and using exercises and other behavioral therapies.    

Sleep Apnea

It is a serious sleep disorder that involves repeated stop and start of breathing. People suffering from sleep apnea may snore loudly and feel tired after sleep. There are three types of sleep apnea including central sleep apnea in which brain does not send required signals to muscles that control breathing.

Second type of sleep apnea is obstructive sleep apnea in which upper airway is partially blocked during shut eye. It is mostly observed in obese people who have thick neck or small airways in nose or throat. Third type of sleep apnea is complex sleep apnea syndrome in which the patient suffers from both obstructive and central sleep apnea.

Sleep apnea is treated by inserting particular devices to open the blocked airways. However, in some complex cases surgeries may be required to treat the ailment (Orr, Malhotra and Sands, 2017).   

REMS behaviour disorder (RBD)

It is a condition in which a person acts out vivid dreams due to absence of normal muscle paralysis during REMS. RBD is caused by malfunctioning of nerve pathways in the brain. It initiates gradually and worsens over time.

It is more common in people who take antidepressants, above the age of 40 or have other neurodegenerative ailments like Parkinson’s disease. Treatments include medications and making the sleep environment safe for the patient (Dauvilliers et al. 2018).

HYGIENE & AMOUNT REQUIRED

Sleep hygiene refers to different practices that are required for a good quality sleep that results in full daytime alertness. Sleep hygiene improves the productivity in daily activities and enhances the overall quality of life.

Amount of sleep required for maintaining a healthy life varies in different age groups. For example, suitable sleep duration for newborns, infants, toddlers, preschool, school-ages, teenagers and adults ranges between 14-17 hours, 12-15 hours, 11-14 hours, 10-13 hours, 9-11 hours, 8-10 hours, 7-9 hours and 7-8 hours, respectively (Hirshkowitz et al. 2015).   

Sleep hygiene is affected
by medical conditions, stress, medications, diet and environment. Different
measures can be taken to improve sleep hygiene. For instance, 

• Daily exercise of 20-30 min helps to improve the
  quality of sleep. 
• Warm bath, reading or other relaxing activities
  before going to bed helps to have a good night’s sleep. 
• Setting biological clock by going to bed and
  waking up at the same times everyday.  
• Avoiding caffeine and nicotine before going to
  bed.
• Taking daytime naps for no more than 20-30 min.
• Avoiding heavy and oily meals at the dinner.
• Sleeping in a room with little or no light, low
  temperature and no noise.   

TESTS AND DIAGNOSIS FOR SLEEP HYGIENE

Sleep abnormalities can be detected by a test called polysomnography. The patient has to spend a night at the sleep testing laboratory where a video and audio of his/her sleep is recorded. Heart rate, breathing rate, oxygen levels, brain waves, limb and eye movements are recorded throughout the night to generate data in the form of a polysomnogram.

Suitable treatments are suggested by the doctors based on the results of polysomnogram (Baglioni et al. 2016). Nowadays, smart technology based watches, rings, bracelets, headbands etc. are also available that can monitor sleep-wake cycle, period of deep sleep, heartbeat and respiration.

These devices are also helpful in analysing data about sleep as their results are close to what may be obtained by polysomnography (Park and Choi, 2019).

FACTS & INFORMATION

• Losing even 1 hr of sleep can affect a person’s
  ability to think and respond. It can significant effects on immune functioning,
  cardiovascular performance and energy homeostasis.
• Quality of sleep is more than quantity of sleep
  because a person having 8-9 hours of sleep may feel unhealthy during the day
  time due to poor quality of sleep.
• Travelling to different time zones or starting a
  night job disturbs the body’s natural biological clock. The body may take more
  than a week to adjust to the new sleep-wake cycle.
• Sleeping for longer time periods on weekends does
  not compensate for missed sleep during the weekdays. In fact, sleeping more on
  weekends disturbs the biological clock and sleeping on Sunday night
  difficult.   

CONCLUSION

In conclusion, quality sleep is essential for good health. Nevertheless, it is mostly ignored as a parameter for good health and well-being. It is recommended to schedule the sleeping time as a priority in daily life routine. Any signs or symptoms related to sleep disorders should not be ignored and consulted with a doctor as any other disease.   

REFERENCES

Baglioni, C., Nanovska, S., Regen, W., Spiegelhalder, K., Feige, B., Nissen, C., Reynolds III, C.F. and Riemann, D., 2016. Sleep and mental disorders: A meta-analysis of polysomnographic research. Psychological bulletin, 142(9), p.969.

Bandyopadhyay, A. and Sigua, N.L., 2019. What Is Sleep Deprivation?. American journal of respiratory and critical care medicine, 199(6), pp.P11-P12.

Carley, D.W. and Farabi, S.S., 2016. Physiology of sleep. Diabetes Spectrum, 29(1), pp.5-9.

Carskadon, M.A. and Dement, W.C., 2005. Normal human sleep: an overview. Principles and practice of sleep medicine, 4, pp.13-23.

Dauvilliers, Y., Schenck, C.H., Postuma, R.B., Iranzo, A., Luppi, P.H., Plazzi, G., Montplaisir, J. and Boeve, B., 2018. REM sleep behaviour disorder. Nature Reviews Disease Primers, 4(1), pp.1-16.

Hirshkowitz, M., Whiton, K., Albert, S.M., Alessi, C., Bruni, O., DonCarlos, L., Hazen, N., Herman, J., Katz, E.S., Kheirandish-Gozal, L. and Neubauer, D.N., 2015. National Sleep Foundation’s sleep time duration recommendations: methodology and results summary. Sleep health, 1(1), pp.40-43.

Lane, J.M., Liang, J., Vlasac, I., Anderson, S.G., Bechtold, D.A., Bowden, J., Emsley, R., Gill, S., Little, M.A., Luik, A.I. and Loudon, A., 2017. Genome-wide association analyses of sleep disturbance traits identify new loci and highlight shared genetics with neuropsychiatric and metabolic traits. Nature genetics, 49(2), p.274.

Orr, J.E., Malhotra, A. and Sands, S.A., 2017. Pathogenesis of central and complex sleep apnoea. Respirology, 22(1), pp.43-52.

Park, K.S. and Choi, S.H., 2019. Smart technologies toward sleep monitoring at home. Biomedical engineering letters, 9(1), pp.73-85.

Peever, J. and Fuller, P.M., 2017. The biology of REM sleep. Current biology, 27(22), pp.R1237-R1248.

Peter-Derex, L., 2019. Sleep and memory consolidation. Neurophysiologie Clinique, 49(3), pp.197-198.