Human beings spend one third of their life span sleeping. Infants and toddlers sleep much more. For many, sleep is the best part of the routine, relieving tiredness and bestowing psychologically soothing effects. In spite of decades of fascinating research, there is no one answer to why we sleep. The evolutionary underpinnings are debatable, but sleep is considered to be a universal biological need in the animal kingdom and a mechanism to conserve energy and restore the body and mind.
The sleep cycle
During a night's sleep, two types of sleep alternate in a cyclical fashion. These two types of sleep have been referred to as the Rapid Eye Movement [REM] Sleep and the Slow Wave Sleep or Non REM sleep [NREM]. REM sleep is interspersed with the NREM sleep, recurring every 90 minutes. Researchers have identified five different stages of sleep, with the first four being NREM which progresses towards REM sleep:
- Light sleep; transition between wakefulness and sleep, muscles begin to relax, person can be easily awakened, 5 - 10 per cent of total sleep time.
- Brain waves [electrical activity recorded via electrodes placed on the skull] slow down with occasional bursts of rapid waves [sleep spindles]. No eye movements. 40 - 50 per cent of total sleep time.
- Characterised by very large and slow brain waves or delta waves interspersed with smaller faster waves.
- More delta activity recorded [stages 4 and 5 constitute 20 per cent of total sleep time]
- REM sleep: 20 - 25 per cent of total sleep time and occurs 4 - 5 times during an 8 - 9 hours sleep period. Duration of REM sleep period varies from 5 - 30 minutes. Decreased muscle tone, irregular heart rate, increase in brain metabolism by 20 per cent are characteristics and the person is cannot be woken up easily by sensory stimuli. Dreams in this stage are vividly recalled even after waking up.
The dream factor
Dreams are mind's natural stress-busters. Psychoanalytically, dreams allow unconscious unfulfilled wishes and fantasies to be acted out in a safe context, which leads to release of anxiety and provides psychological balance. Dreams have also been widely interpreted to understand the unconscious mechanisms of the mind, thus revealing more about one's mental health.
While the average adult requires one third of the day i.e. eight hours, children usually need 9-10 hours of a night's sleep to feel fresh. However, modern lifestyle forces people to make do with 5-6 hours of sleep. The level of fatigue does not determine the hours of sleeping, instead it determines the length of REM sleep. Hence, the more fatigued you are, the less of REM sleep and the more of deep sleep you tend to get.
Research shows that metabolic activity of the brain decreases significantly after 24 hours of sustained wakefulness. Sleep deprivation [which researchers claim can be more dangerous than food deprivation], other medical complications, environmental conditions like light and disturbed levels of the hormone melatonin can lead to sleep disorders. It can also lead to an eventual decrease in immune system functioning as measured by white blood cell count, and decrease in the release of growth hormones.
The biological clock
An internal biological clock regulates the timing for sleep in humans. The activity of this clock makes us sleepy at night and awake during the day. Our clock cycles with an approximately 24-hour period and is called a circadian clock. The most important function of a biological clock is to regulate overt biological rhythms like the sleep/wake cycle. The cue that synchronises internal biological clock to the environmental cycle is light.
Upset circadian rhythm
- Effect on travellers: Jet lag results from the inability of our circadian clock to make an immediate adjustment to the changes in light cues that an individual experiences when rapidly crossing time zones. It produces a number of unwanted effects including excessive sleepiness, poor sleep, loss of concentration, poor motor control, slowed reflexes, nausea, and irritability.
- Monday morning blues: By staying up and sleeping in an hour or more than usual on the weekends, we provide our biological clock different cues that push it toward a later night time phase.
- Shift work: Modern society requires that services and businesses be available 24 hours a day. So, some individuals must work the night shift. These individuals no longer have synchrony between their internal clocks and external daylight and darkness signals.
- Lack of sunlight: Very little light reaching the biological clock in the SCN [a group of cells in the hypothalamus] appears to bring on this recognised form of depression in susceptible individuals.
Voluntary behaviour: People who engage in voluntary, but unintentional, chronic sleep deprivation are classified as having a sleep disorder called behaviourally induced insufficient sleep syndrome. This is a type of hypersomnia. It involves a pattern of restricted sleep that is present almost daily for at least three months.
Personal obligations: Sleep deprivation can occur when personal obligations restrict sleep time. For example, a person may lose sleep while providing home care for a relative with a chronic illness.
Work hours: The work hours required by some occupations can produce sleep deprivation.
Medical problems: Sleep deprivation may be a symptom of an ongoing sleep disorder or other medical condition that disturbs sleep.
- The primary effect of sleep deprivation is excessive daytime sleepiness. This degree of severe sleepiness can be a safety hazard, causing accidents while driving and workplace injuries.
- Mood becomes irritable, anxious, depressed and shows lack of motivation.
- Performance will also be hampered due to lack of energy, coordination and concentration.
- Sleep deprivation has been associated with an increased risk of high blood pressure, heart attack, obesity and diabetes.
The remedy lies in use of sleep hygiene techniques and consulting professionals if the problem becomes severe. Sleep hygiene begins with arranging basic necessities for a good night's sleep:
- A comfortable bed reserved only for sleeping at night
- Absence of lights and loud noises
- Fixed time to sleep and wake up everyday
- Day time sleeping is discouraged to ensure accumulation of fatigue at the end of the day
- Intake of caffeine, alcohol or watching bright screens like TVs and computers should be avoided at least since two hours before bedtime
- Dinner should be light and balanced in carbohydrates and proteins
- A glass of warm milk just before going to bed, also helps in inducing sleep, since warm milk contains tryptophan which stimulates secretion of sleep-inducing hormone, melatonin.
Sleep is essential for a person's overall wellbeing. It is therefore advisable to work one's routine in a manner that one gets the desired amount of sleep. This helps fight stress with the body's natural restoring mechanism, thus maintaining an integrated physical, mental and spiritual wellbeing.
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