August 20, 2022 5 min read
Getting rest after a long day at work can be one way to recover from fatigue; more importantly, how much time spends sleeping directly affects how one performs at work. This article discusses the amount of time to spend sleeping.
The body goes through four stages of sleep, including REM and NREM. The body cycles through these stages 4–6 times, lasting 90 minutes. Fewer NREM stages occur later in the night, and REM sleep periods last longer. The circadian rhythm regulates sleep, which varies throughout life. Newborns spend over 50% of their total sleep in REM, often instantly entering REM. Initially, newborns sleep in brief bursts of 12 to 18 hours. From 5 to 10, children's sleep requirements drop to 10 hours. Teenagers need 8–9 hours and adults 7–8 hours. Our circadian clock also regulates the nighttime release of adrenocorticotropic (ACTH), prolactin, melatonin, and norepinephrine, all critical hormones for regular body function.
According to Ghasemzadeh et al. (2019), sleep phases are broken down into five stages, i.e., wake, N1, N2, N3, and R. these stages are progressive, and as one spends the more time sleeping, the more they are likely to get into a deep sleep which is highly beneficial. These stages last around ninety minutes each, and the body can repeat these stages up to six times a single night, depending on the amount of time one spends sleeping. Below is a discussion of each stage. Sleep is divided into minute pockets of thirty-second epochs, and each epoch is assigned a different name at different stages.
Carskadon& Dement (2005) showed that Stage W is the first stage, and it lasts between five to ten minutes and is considered the shortest of the cycles. This phase majorly relies on whether the eyes are open or closed. This stage causes us to feel tired and calm. Power naps should be no more than twenty minutes to avoid deep sleep. Too long a nap might cause a deep sleep awakening, leaving you tired. Eyes wide, there are alpha and beta waves, mostly beta. The alpha rhythm is dominant as people fall asleep and their eyes close. Patel et al. (2021) indicated that stage W epochs are considered complete when it features more than 50% alpha waves and eye movements associated with wakefulness.
Jawabri& Raja (2019) noted that this is the lightest stage of sleep, which begins when more than half of the alpha waves are replaced by low-amplitude mixed-frequency (LAMF) activity. Muscle activity in this stage is toned down to a regular rhythm, wherever it is present in areas such as the skeletal muscle and the diaphragm, where breathing occurs regularly. This stage typically lasts 1 to 5 minutes and accounts for around 5% of the whole cycle. This stage is important to the muscles as it prepares various body muscles for repairs and rest.
According to Blagrove et al. (2011), as an individual enters this stage, the circadian rhythm slows down the heart rate and body temperature; this enables one to enter a deeper sleep state. The existence of sleep spindles, K-complexes, or both distinguishes it from other stages. These sleep spindles activate the superior temporal gyri, anterior cingulate, insular cortices, and thalamus. The K-complexes indicate a shift towards a deeper state of sleep. They are a single, lengthy delta wave that lasts only a second. As the individual falls deeper into sleep, they enter N3. Delta waves will replace all of their waves. Stage 2 sleep lasts around 25 minutes in the first cycle and gradually increases in length with each subsequent cycle, eventually accounting for nearly half of total sleep.
Patel et al. (2021) explained that this is the deepest sleep stage, distinguished by significantly slower frequency and high amplitude signals known as delta waves. This is the most difficult stage to awaken from, and for some people, even loud noises (over 100 dB) will not bring them up. As adults age, they spend less time in slow, delta wave sleep and more time in stage N2 sleep. If someone is awoken during this stage in their sleep cycle, they will experience a brief period of mental fogginess known as sleep inertia. Individuals who awaken during this period have considerably impaired mental performance lasting between 30 minutes to an hour. The body heals and regrows tissues, produces bone and muscle, and fortifies the immune system. Thus, it is important to anyone sleeping.
Schlemmer et al. (2015) stated that this is the stage in which you dream. Surprisingly, the electroencephalogram (EEG) reading at this stage is similar to that of an awake person, yet the skeletal muscles are atonic and non-moving. The ocular and diaphragmatic breathing muscles, on the other hand, remain active. On the other hand, the breathing rate has changed, becoming more chaotic and irregular. This stage normally begins 90 minutes after you fall asleep, and each REM cycle becomes longer throughout the night. The first phase is usually 10 minutes long, and the last one might run-up to an hour.
Li et al. (2021) noted that various factors affect the amount of sleep one needs, including age, nature of work, and sex of the individual. However, infants below three months generally need between fourteen to seventeen hours of sleep. Infants aged between four months to eleven months require at least twelve hours of sleep, up to fifteen hours. Between one and two years, Toddlers would generally carry on the day with eleven hours of sleep. Generally, kids below thirteen years should spend at least ten hours of sleep for maximum benefits. Teenagers require at least eight to ten hours of sleep. Adults need between seven to eight hours of sleep, but this figure can range from six hours to ten hours. The aged population, i.e., above sixty-five years of age, needs at least eight hours of sleep. On the other hand, pregnant women might need more sleep than is usual due to the fetus.
There are at least four stages of sleep, i.e., wake, N1, N2, N3, and REM sleep which are distinct and aid the body in different ways. Sleep cycles last for about ninety minutes and increase progressively as one spends more time sleeping and can repeat up to six to seven times a night. Generally, sleep is needed at one age, and adults can spend at least six hours sleep, although this may vary from individual.
Blagrove, M., Fouquet, N. C., Henley-Einion, J. A., Pace-Schott, E. F., Davies, A. C., Neuschaffer, J. L., & Turnbull, O. H. (2011). Assessing the dream-lag effect for REM and NREM stage 2 dreams. PLoS One, 6(10), e26708.
Carskadon, M. A., & Dement, W. C. (2005). Normal human sleep: an overview. Principles and practice of sleep medicine, 4(1), 13-23.
Ghasemzadeh, P., Kalbkhani, H., & Shayesteh, M. G. (2019). Sleep stages classification from EEG signal based on Stockwell transform. IET Signal Processing, 13(2), 242-252.
Jawabri, K. H., & Raja, A. (2019). Physiology, sleep patterns.
Li, L., Nakamura, T., Hayano, J., & Yamamoto, Y. (2021). Age and gender differences in objective sleep properties using large-scale body acceleration data in a Japanese population. Scientific reports, 11(1), 1-11.
Patel, A. K., Reddy, V., & Araujo, J. F. (2021). Physiology, sleep stages. In StatPearls [Internet]. StatPearls Publishing.
Schlemmer, A., Parlitz, U., Luther, S., Wessel, N., & Penzel, T. (2015). Changes of sleep-stage transitions due to ageing and sleep disorder. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 373(2034), 20140093.
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