Many people spend large portions of their lives working, often to the detriment of their sleep. Sleep repairs the physical body to improve and maintain general health, consolidate learning and memory, and recharge the psychological batteries to maintain emotional balance and well-being. Quality sleep is as important as nutrition or exercise in maintaining overall health. A nutritious diet provides vitamins and minerals to maintain body functions and generate sufficient energy to perform daily activities whereas regular exercise keeps muscles toned, improves cardiovascular activity, and reduces stress. However, neither diet nor exercise replaces the need for sleep.

According to the National Sleep Foundation, young adults (age 18-25 years) and adults (age 26-64years) should receive 7 to 9 hours of sleep but not less than 6 hours or more than 10 hours (for adults) or 11 hours (for young adults). Older adults (65years and older) should receive 7 to 8 hours of sleep but not less than 5 hours or more than 9 hours.

The circadian clock is a specialized clock generator of the human body and represents an essential part of a healthy metabolism. The intrinsic circadian rhythm can be modulated by exogenous factors such as light / darkness, behaviour patterns, physical activity, eating habits and lack of sleep or sleep disorders. Light plays an essential role in the circadian rhythm. As natural light disappears in the evening, the body will release melatonin, a hormone that induces drowsiness. When the sun rises in the morning, the body will release the hormone known as cortisol that promotes energy and alertness.

According to the National Heart, Lung, and Blood Institute, people with sleep deficiency have a greater risk of many health complications, including heart disease, kidney disease, high blood pressure, diabetes, stroke, and obesity. Current studies show that quantitative and qualitative changes in sleep patterns are significantly associated with an increased prevalence of obesity. In addition, a restricted duration and quality of sleep can lead to reduced glucose tolerance and insulin sensitivity and thus increase the risk of diabetes.

Stages of Sleep

Once we fall asleep, our bodies follow a sleep cycle which is divided into four stages. The first three stages are known as non-rapid eye movement (NREM)sleep, and the final stage is known as rapid eye movement (REM) sleep.

• Stage 1: This stage marks the transition between wakefulness and sleep, and consists of light sleep. Muscles relax and your heart rate, breathing, and eye movements begin to slow down, as do your brain waves, which are more active when you are awake. Stage 1 typically lasts several minutes.
• Stage 2: This second sleep stage is characterized by deeper sleep as your heart rate and breathing rates continue slowing down and the muscles become more relaxed. Eye movements will stop and your body temperature will decrease. Apart from some brief moments of higher frequency electrical activity, brain waves also remain slow. Stage 2 is typically the longest of the four sleep stages.
• Stage 3: This stage plays an important role in making you feel refreshed and alert the next day. Heartbeat, breathing, and brain wave activity all reach their lowest levels, and the muscles are as relaxed as they will be. This stage will be longer at first and decrease in duration throughout the night.
• Stage 4(REM): The first REM stage will occur about 90 minutes after you fall asleep. As the name suggests, your eyes will move back and forth rather quickly under your eyelids. Breathing rate, heart rate, and blood pressure will begin to increase. Dreaming will typically occur during REM sleep, and your arms and legs will become paralyzed – it’s believed this is intended to prevent you from physically acting out on your dreams. The duration of each REM sleep cycle increases as the night progresses. Numerous studies have also linked REM sleep to memory consolidation. The duration of the REM stage will decrease as you age, causing you to spend more time in the NREM stages

These four stages will repeat cyclically throughout the night until you wake up. For most people, the duration of each cycle will last about 90-120 minutes. NREM sleep constitutes about 75% to 80% of each cycle. You may also wake up briefly during the night but not remember the next day. These episodes are known as “W” stages.

Factors which affect sleep

1. Stress is the number one cause of short-term sleeping difficulties, according to sleep experts. Common triggers include school- or job-related pressures, a family or marriage problem and a serious illness or death in the family. Usually the sleep problem disappears when the stressful situation passes. However, if short-term sleep problems such as insomnia aren't managed properly from the beginning, they can persist long after the original stress has passed.
2. Drinking alcohol or beverages containing caffeine in the afternoon or evening, exercising close to bedtime, following an irregular morning and night time schedule, and working or doing other mentally intense activities right before or after getting into bed can disrupt sleep.

3. Shift work forces you to try to sleep when activities around you — and your own "biological rhythms" — signal you to be awake. One study shows that shift workers are two to five times more likely than employees with regular, daytime hours to fall asleep on the job.
4. Travelling also disrupts sleep, especially jet lag and traveling across several time zones. This can upset your biological or “circadian” rhythms.
5. Environmental factors such as a room that's too hot or cold, too noisy or too brightly lit can be a barrier to sound sleep. And interruptions from children or other family members can also disrupt sleep. Other influences to pay attention to are the comfort and size of your bed and the habits of your sleep partner. If you have to lie beside someone who has different sleep preferences, snores, can't fall or stay asleep, or has other sleep difficulties, it often becomes your problem too!

Tips on how to sleep better

• Establish a realistic bedtime and stick to it every night, even on the weekends.
• Maintain comfortable temperature settings and low light levels in your bedroom.
• Make sure you have a comfortable sleep environment – including your mattress, pillows, and sheets.
• Consider a “screen ban” on televisions, computers and tablets, cell phones, and other electronic devices in your bedroom.
• Abstain from caffeine, alcohol, and large meals in the hours leading up to bedtime.
• Refrain from using tobacco at any time of day or night.
• Exercise during the day; this can help you wind down in the evening and prepare for sleep.
• Minimize noise, light and excessive hot and cold temperatures where you sleep.
• Try and wake up without an alarm clock.
• Attempt to go to bed earlier every night for certain period; this will ensure that you’re getting enough sleep.

References

1. Meyhöfer, S., Wilms, B., Oster, H. et al. The importance of the circadian sleep rhythm for energy metabolism. Internist 60, 122-127 (2019). https://doi.org/10.1007/s00108-018-0543.
2. Lichtenstein G. R. (2015). https://www.sleepfoundation.org/how-sleep-works/why-do-we-need-sleep. Gastroenterology & hepatology, 11(12), 790.
3. Ohlmann, K. K., O'Sullivan, M. I., Berryman, P.,& Lukes, E. (2009). The costs of short sleep. AAOHN journal, 57(9),381-387.
4. Spiegel, K., Tasali, E., Leproult, R. et al. Effects of poor and short sleep on glucose metabolism and obesity risk. Nat Rev Endocrinol 5, 253–261 (2009). https://doi.org/10.1038/nrendo.2009.23.
5. B.,R., & Born, J. (2013). About Sleep’s Role in Memory. Physiological Reviews,93(2), 681–766. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768102/.
6. Fry, A. (2020). Why Do We Need Sleep? [Internet]. Online. Sleep Foundation. Available from: https://www.sleepfoundation.org/how-sleep-works/why-do-we-need-sleep.
7. American Psychological Association. (2020). Why Sleep is Important. [Internet]. Online. APA. Available from: https://www.apa.org/topics/sleep/why

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