The Science Behind Why Sleep

Normally, one tends to believe that when a person sleeps, the brain and the body are in a type of a shutdown mode. However, this is not the case. Sleep constitutes an active period in which the human body goes through some very important processes which lead to restoration as well as the strengthening of many body constituents and functions. While it remains a mystery as it exactly how it all happens and how the body has been programmed to go through to this rather long period of slumber. However modern science has succeeded in unraveling at least a part of the mystery and figured out the critical functions of sleep as well as the reasons one needs sleep to have optimal health as well as wellbeing 1.

The importance of Sleep

The importance of sleep has been associated with its relationship with brain health as well as peoples’ wellbeing throughout their lives.  Instead of concentrating on particular sleep disorders, neurologists and scientists prefer to concentrate on the fact that sleep is not just an indicator of any particular sleep disorder or even neurological disease, but in fact, it is a vital function related to brain health and function. Regardless of where a person is located or engaged in a certain occupation, sleep is crucial in determining that both the body and the mind are performing to their level best. Sleep is so profound and pervasive to all people, and therefore, the gauging of sleep quality is fundamental to understanding the person’s wellbeing as much as the vital signs. In the early days of sleep-related research, scientists had concentrated on the complex processes that go on in the human mind and body which related to human biorhythms. Such studies tended to gauge the importance of sleep throughout the life of an adult and how different stages of life are affected by having a quality sleep or otherwise. Moreover, scientists have also studied sleep in elderly people to ascertain the effects of disruptions in human biorhythms and their effect on human brain health and sleep. They seem to tie the human biorhythms and sleep to the proper functioning of the brain and disruptions in the circadian rhythm to accelerated neurodegeneration (degeneration of the neurological functions). 2.

More often than not, sleep is not taken very seriously by most people.  Even, almost half of those people who suffer from sleep-related issues like sleep apnea do not accept that they require medical help. Most of the people consider sleep to be something that determines whether a person is alert or tired. However, sleep is a lot more than just that. It can even end up saving a person’s life if the causes of disruption in sleep are determined and remedial action taken. For the mind and the body to work properly, sleep is a must. If one does not take it seriously and continue to stay awake for long hours, and if the lack of sleep becomes continuous, this could even prove to be fatal. One must be thankful if one can sleep well. Currently, 70 to 80 million people in the United States have insomnia which leads to either not being able to sleep when one should or once slept, stay sleeping for longer hours well beyond the time that one should be up. To such people, sleep becomes a luxury. For other people, it is something that they take it for granted, and some are so careless, they even abuse it 3.

Studying Sleep Deprivation (SD) to Gauge the Importance of Sleep

In the modern world, staying awake for long hours has become a widespread phenomenon. While sleep deprivation in the form of partial sleep restriction has been more common in the world today, scientists have concentrated more on what they describe as total sleep deprivation. Thus whether sleep deprivation (SD) is partial or total, it has been observed that they impact the cognitive functions of the brain and as such, have a direct bearing on cognitive performance. SD has a direct impact on working memory and also disrupts attentiveness. However, this is not all.  Prolonged sleep deprivation would start to affect long-term memory as well and even impact the decision-making capabilities of an individual. Partial Sleep deprivation can lead to a negative impact on attentiveness and is particularly impeding when it comes to ‘vigilance.’ Although there have not been too many studies conducted on determining the effects of partial SD on cognitive functions, it is nonetheless extremely important to recover from this state. Scientists have observed that the recovery process leading to cognitive functions restoration involved in the case of partial SD is even more demanding as compared to the one involving total SD 4.

Quality of Life Disruption due to Sleep Loss

While there might be a lot of reasons that might lead to the disruption on the quality of life of an individual, one such reason is indeed sleeping loss or deprivation. A 2018 poll conducted by the National Sleep Foundation in the United States shows that among the adults in the United States, who have great sleep health and sleep quality, 90% of these people claim that they are quite effective at getting around in life and getting things done the way they want. This contrasts sharply with 46% of those adults who are sleep deprived even partially and who are capable enough to get things done the way they want. There is a serious lack of preauthorization of ‘sleep’ as an important factor to consider for healthy living as compared to other activities such as nutrition/fitness, social life, work, as well as personal interests/hobbies, etc.5.

Lack of planning

The same poll also reveals that 65% of the public in the United States believes that if they can get enough sleep, they would be able to become more effective. However, 41% of the population is forced to admit that they rarely consider the fact that they do not plan on how much sleep they would be having the very next day. Regardless of whether one is a child or an adult, the majority in the United States seem to be ‘overscheduled’ consistently. The reason behind this problem is simple to understand. They just do not ‘reserve’ enough time to accommodate for sleep daily as a part of their daily routine planning. National Sleep Foundation manages the Sleep Health Index every quarter which has been rather consistent in the recent past, and the overall score has lingered around 76 out of a total of 100 for quite some time now. In the 2018 poll, the highest shift was noticed in at least one aspect which is related to sleep duration. This aspect has improved for American adults in terms of getting more sleep on weekdays. However, there are still some disturbing statistics lurking in the low ranges. One of these is the ‘sleep quality’ which stood at 67 in the 2018 poll 5.

Vital Role of Sleep

One of the many vital roles of sleep is to help people consolidate and solidify their memories. As an individual goes about going through his daily routine, an incredible amount of information is fed into the brain.   The information does not directly get logged r stored in the manner; it happens in computers. These facts, as well as the experiences of the human being, are first processed by the brain and are then stored. However, a lot of these vital steps take place when the person is asleep and not awake. Bits and pieces of information are transferred overnight from the short term or tentative memory to the much stronger long-term term memory. This process, which takes place while the person sleeps, is referred to as ‘consolidation.’ Scientists and researchers have also found out that people tend to retain information and perform even better on memory-related tasks after sleep.  To restore the body and mind and rejuvenate them, a person needs to sleep for long hours.  The body also grows muscles, synthesize hormones, repairs tissues, regenerate bones, etc. all during the time the person is asleep 1.

Physical Restoration through Sleep

Many theories have been put forward to explain the need for sleep for physical restoration.  The body goes through both growth and repair during sleep; however, a lot is still a mystery. Quite recently, 6 Schmidt presented a theory which is centered on the concept of allocating limited energy resources to different necessary biological processes.  This is referred to as the Energy Allocation model of sleep. According to Schmidt, the sleep-wake cycle has evolved to conduct essential biological processes while sleeping to conserve energy during sleep. According to this theory, the optimal energy consumption is obtained through the sleep-wake cycles. This keeps the total energy spent at an optimal level.  Researchers who strongly favor the restorative function of sleep note that the hormones released during the time a person sleeps usually have an anabolic function, e.g. the human growth hormones. Whereas, the hormones that are predominantly released during the wake time, have what the scientists refer to as the catabolic effect, e.g., the release of cortisol.  This function does not occur while the person is asleep 7

Optimal Use of Energy

Lower energy levels are noted during sleep. Thus, the energy costs on the human body are lower during sleep as compared to the cost during the wake time. Researchers CM Jung and colleagues had evaluated7 healthy participants in a study, and their ages were in the range of 22 ± five years.  They were allowed to sleep normal and also sleep deprived at different times. They were also studied during recovery. They found out that during twenty-four hours that the energy costs went up by 7% during the sleep deprivation period and went down by 5% during the recovery period 8. Despite such studies, while the researchers are confident about the strong role of sleep for human growth, there is still a need for further studies to dig deeper to uncover more facts. Researchers have also found out that if the sleep time is not adequate and the person is subjected to sleep deprivation over long periods, it could lead to problems like obesity and weight gain. If a person is deprived of sleep, many other factors start to creep in and start playing a significant role. These could result in an unnecessary increase in appetite. The person can start feeling hungrier, and the result would be a higher food intake leading to long term weight gain as well as obesity 9.

Immune System

The effect of proper sleep on immune system regulatory functions as well as the negative effects of sleep deprivation on the immune system are not yet very well understood.  However, a lot of research work done recently has indicated that sleep tends to enhance the early stage of the immune response put forward by the immune system of the body against any threat 10.. A study carried out to test this involved studying the immune system response in 27 healthy males after taking hepatitis A virus vaccinations. These men were made to either stay awake after they had taken the vaccine or allowed to sleep.  The ones who had gone to sleep were tested to reveal that the frequency of antigen (Ag)-specific T helper (Th) cells had doubled in them.  This process occurred during the early stages of the slow wave sleep in the first night after taking the vaccine. For those who were deprived of sleep, it was observed that their gnomonic and cellular mechanisms were disturbed.

Mortality and Sleep

Interestingly, while the 7-hour sleep duration for adults was found to be the most optimal one in terms of all-cause mortality, the ones who sleep more than 7 hours and those who are sleep-deprived, i.e., sleep for less than 7 hours showed a higher risk of all-cause mortality. In another study, it was found out that those people who slept for less than 5 hours a day as compared to the required 7 hours of sleep, the incidence of obesity, higher body mass index, hypertension, diabetes, stroke, heart attack, and hypercholesterolemia were higher as compared to those individuals who normally sleep for 7 hours a day. It was also found out that those who are sleep-deprived tend to face a higher risk of blood pressure, heart rate issues, etc. These could be symptomatic of unnecessary higher nervous system activity 11.

Sleep and Bone Repair

Human bones continue to repair throughout the life of the human being. There is regular removal of bone tissue taking place from the skeleton, and it is continuously replaced with newly formed bone tissue. This is referred to as bone metabolism or bone remodeling.  This regeneration or remodeling leads to the maintenance of strength, bone density, as well as the flexibility of the bones.  The process of bone remodeling is invoked in the case of a bone injury as well when bones need to be repaired.  The bone remodeling process is equally effective regardless of whether the bones need to be repaired after an injury or they have gone through micro-damage as a result of regular wear and tear of bones. The bone remodeling process would kick in regardless of the cause.  It starts to repair and replace the damaged parts of the bones. If an individualist is sleeping normally, i.e., adult sleeping for 7 hours daily, the bone remodeling process is quite optimal and functions properly. However, in the case of sleep deprivation, serious abnormalities in the bone and bone marrow might creep in, thereby disrupting the natural process. An experiment in animals at a laboratory at the Medical College of Wisconsin found out that sleep-deprived animals had stopped forming new bones and their bone density had started to fall gradually. Bone flexibility also got reduced due to the effects of sleep deprivation on bone marrow.  It is extremely important to have flexible bones to prevent fractures. The same study went on to prove that humans behave similarly.  The bone remodeling process stays normal as long as the sleep is normal but starts to be disrupted with increasing sleep deprivation.  For many people in this fast-moving world which tends to deprive them of sleep, this fact is very important to note. The decrease in bone density, in the long run, could lead to osteoporosis in the old age 12.

Study on Sleep Deprivation and Bone Repairs Markers

The America Sleep Association reported a study in 2017 through which it endeavored to understand the link between insufficient sleep and its effects on bone formation. The study was funded by the National Institute on Aging and the Medical Research Foundation of Oregon along with the National Institute of Arthritis and Musculoskeletal and Skin Diseases. The study involved ten healthy men who were subjected to 3 weeks of insufficient sleep consecutively.  The blood analysis carried out at the end of the three weeks showed that the marker of bone formation had gone down in concentration in their bodies.  The results were then compared with the results of those people who normally suffer from such factors as jet lag or who attend work in shifts. For those people with jet lag and shift work, the bone resorption marker had not changed. The research concluded that insufficient sleep could lead to altered bone balance as a result. In 2017, there were at least 54 million Americans who were suffering from either osteoporosis or had low bone mass density. However, 50% of these people have not yet been given or diagnosed a reason for the low bone mass. It is quite possible that insufficient sleep or chronic sleep disturbance could turn out to be a valid cause of such an affliction 13.

The Centers for Disease Control and Prevention have reported that at least 25% or more of the population in the United States gets insufficient sleep on some occasions.  10% of the population according to their data, gets insufficient sleep frequently. These are disturbing statistics as they show a lack of giving priority or lack of planning about the importance of sleep in peoples’ everyday lives. The study had also analyzed the disruption of the circadian rhythm as well as the health consequences of sleep deprivation. The study simulated what happens to those people who do shift work or suffered from jet lag. The similarities were arranged in such a way that the study enabled a scenario in the lab equivalent to flying four time zones in the United States each day for three weeks. The subjects were made to sleep 4 hours later as compared to the previous day. Thus, each day became a day having 28 hours for them.  They could also not sleep for more than 5 or 6 hours in every 24 hours. Blood tests were conducted before the study and after three weeks as well.  The biomarkers for bone repair were measured in each case. The subjects had been given the same type of nutrients in the same quantities during the 3 weeks.  Six of the men were in the age group of 20 to 27 while four fell between the 55-65 age range 13.

All of the data and information presented above clearly indicate that proper sleep is necessary to ensure the smooth functioning of the heart, the immune system, optimal energy utilization, bone remodeling and repair, muscle growth and the overall health and wellbeing of an individual. Sleep deprivation extended over long periods could seriously affect any or all of the above and can cause serious health issues in the long run. For anyone wanting to avoid serious health issues including chances of getting osteoporosis at an old age, he/she must consider attaining quality sleep and start to properly prioritize and plan for sleep for every coming day as a part of his/her daily routine. Healthy sleep daily would ensure that the metabolism of the body would function properly and would not be subjected to harms related to sleep deprivation thereby causing the body’s immune system, and the bone remodeling mechanisms to function smoothly. The nervous system, as well as the heart, would not come under pressure, and the individual would tend to live a healthy and normal life for long.

References

1NSF. (2019). Why do we Need Sleep? Retrieved from National science foundation: https://www.sleepfoundation.org/articles/why-do-we-need-sleep

2Schneider, L. (2019). The Importance of Sleep. Retrieved from Practical Neurology: https://practicalneurology.com/articles/2019-mar-apr/the-importance-of-sleep

3Stevenson, A. (2019). Why Sleep is important? Retrieved from American Sleep Association: https://www.sleepassociation.org/about-sleep/how-important-is-sleep/

4Polo-Kantola, P. A. (2007). Sleep deprivation: Impact on cognitive performance. Neuropsychiatr Dis Treat., 553-567.

5Colbert, T. (2018). 2018 Sleep in America Poll. National Science Foundation.

6Schmidt, M. (2014). Physical Restoration through sleep. Neurosci Biobehav Rev 47(0), 122-153.

7Weitzman E D, N. C. (1974). Effects of a prolonged 3-hour sleep-wake cycle on sleep stages, plasma cortisol, growth hormone, and body temperature in man. J Clin Endoc Metab 38(6), 1018-1030.

8Jung CM, M. E. (2011). Energy expenditure during sleep, sleep deprivation, and sleep following sleep deprivation in adult humans. J Physiol 589 (Pt 1), 235-244.

9Spiegel, K, T. E. (2004). Brief communication: sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Int Medi 141(11), 846-850.

10Lange T, D. S. (2011). Sleep after vaccination boosts immunological memory. J Immunol 187(1), 283-290.

11Samson Z Assefa, M. D.-A. (2015). The Functions of Sleep. Neuroscience Volume 2, Issue 3, 155–171.

12SO. (2019). Sleep Habits And Your Bone Health. Summit Orthopedics, https://www.summitortho.com/2015/03/06/sleep-habits-bone-health/.

13 ASA. (2017, April 5). Sleep Deprivation Can Lead to Loss of Bone Formation. Retrieved from American Sleep Association: https://www.sleepassociation.org/sleep-news/sleep-deprivation-can-lead-loss-bone-formation

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