Sleep is a basic necessity in everyday life. This is because during sleep, the body replenishes its used up supplies. A good night’s sleep can lead us to feel refreshed and invigorated all throughout the day. A recent study shows that poor sleep can lead to cognitive decline in older men in only about three to four years.
The Importance of Sleep
Without sleep, we all cannot survive. Good sleep has a lot of health benefits. Before we go to its various benefits, let us take a closer look first on what sleep really is.
Sleep is composed of different stages that form a cycle throughout the night. Good sleep is not just all about how many hours you have slept but also on how much of the various stages of sleep you get each night. The brain is responsible for these stages because it never actually sleeps while you sleep. The brain gives out a distinctive pattern of electrical activity known as brain waves during sleep. There are two types of sleep: rapid eye movement (REM) sleep and non-REM sleep. Non-REM sleep is composed of four different stages. Usually when a person sleeps, stage non-REM sleep starts, in which he or she sleeps lightly and can be easily awakened by noises or other disturbances. During this stage, the eyes move slowly and there is slowing down of muscle activity. Stage 2 non-REM sleep then ensues wherein the eye movements stop. During this stage, the brain gives out slower brain waves with occasional bursts of rapid waves.
The body then goes into stage 3 non-REM sleep, wherein brain waves become slower. After this, stage 4 non-REM sleep occurs wherein the brain produces extremely slow waves. Looking back at these stages, stage 3 and 4 are considered to be deep sleep, the restorative type of sleep that is needed for one to feel energetic and well rested all throughout the day.
On the other hand, during REM sleep, there is rapid movement of the eyes in various directions despite the fact that the eyelids remain closed. During this type of sleep, the breathing also becomes more rapid, shallower and more irregular and there is increase in the blood pressure. This is the type of sleep where dreaming occurs and where limb muscles are paralyzed.
So what makes a person sleep? This may be due to a substance produced by the body known as adenosine. Adenosine builds up in the blood after there is increase in wake time. During sleep, the body breaks down adenosine. Accumulation of sleep after many nights of staying late is due to the buildup of adenosine in the body.
The time for sleeping is also affected by your biological clock inside the body. This biological clock is governed by your exposure to light and darkness. The biological clock is actually made up of tiny cells in the brain which respond to light signals emitted from your eyes. When there is darkness, this biological clock triggers the body to produce melatonin, a hormone that makes you sleep. Melatonin can bring about drowsiness and yawning and can increase during nighttime. Melatonin is increased from midnight until 7 in the morning, and there is a second peak between 1 p.m. and 4 p.m.
During the day, your biological clock keeps you awake. Thus staying up late at night and working late night shifts can destroy the biological clock and can lead to hormonal imbalances. This can create sleep debt which is especially dangerous to night shift workers because they are more prone to road and industrial accidents when they work on an extended shift.
There are also other factors that govern sleep such as the immune system’s production of cellular hormones called cytokines. These are substances produced by the body in response to infections and inflammations that make you sleep more than usual. This sleep may actually help your body fight against infection by boosting your immune system. Other factors that may influence sleep include sleeping habits, jet lag, intake of caffeine and medications and intake of alcohol.
Sleeping and Cognitive Health
A new study has shown that there is a link between poor sleep quality and cognitive decline in about three to four years. This study involved 2,822 community-dwelling older men at six clinical centers in the U.S., the results of which are published in the April 1 issue of the journal Sleep. The results showed that cognitive decline can be due to poor sleep quality in these older men. Cognitive function assessment in these subjects included evaluation of attention and executive function using the Trails B test. The underlying mechanisms relating disturbed sleep to cognitive decline still remain unknown.
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