Sleep is something that every living organism does, but although all living organisms do it, we still have a lot to learn as to why we sleep. As humans, we spend one-third of our lives snuggled up and cozy in bed. A healthy person usually has a very healthy sleeping pattern. Deprived sleep and irregular sleep patterns are known to have a common link with different health issues, which signals that the quality of your sleep also determines the quality of our health. Before we investigate the effects of sleep on the body, let’s look at the different stages of sleep.
The average sleep cycle is usually 90 minutes, and during this time, we move through four stages of sleep. These four stages can fall under two broad spectrums: Non-Rapid Eye Movement (NREM) and the Rapid Eye Movement (REM) sleep.
NREM sleep is the part that contains the first three stages of sleep. Stage 1 of sleep is considered the lightest stage of sleep. It is usually defined as the stage of sleep where slow eye movement occurs. This stage of sleep is known as the drowsy stage of sleep. A person can easily be disturbed during this stage. Muscle tension reduces as the body relaxes and brain waves also slow down. Other sensations include hypnic jerks or muscle spasms; some people also experience the sensation of falling.
Stage 2 of sleep is considered to be the first actual NREM stage of sleep. It is not very easy to wake up during this stage of sleep, and slow eye movement stops. Brain waves considerably slow down, and there are short bursts of rapid eye movement known as sleep spindles with a mix of K complexes. Sleep spindles are sudden bursts of oscillatory brain activity. The electrical activity of the sleep spindles occurs either globally or locally in the brain. There are two kinds of spindles: fast spindles, which occur in the centroparietal region of the brain (13-15 Hz); and slow spindles, which occur in the frontal lobe of the brain (11-13 Hz). The K complexes that occur during Stage 2 of the sleep cycle are not rapid bursts of activity, but rather large waves that react to the external stimuli.
Deep sleep occurs in Stage 3 of NREM sleep. The brain waves during this stage of sleep are known as delta waves. These waves have a slow speed and a large amplitude. This stage of sleep is usually referred to as the most restorative stage of sleep. Waking a person up from this stage of sleep is quite difficult, as people do not easily respond to external stimuli. Deep sleep also reduces sleep drive. That is why most people observe that when they have a short nap, they can sleep at night, but if they have a long nap where they go into a deep sleep, they will be unable to sleep at night. In a deep sleep, human growth hormone is released and restores your body and muscles from the stressors of the day. Your immune system also restores itself. Much less is known about deep sleep than REM sleep. It may be during this stage that the brain also refreshes itself for new learning.
The final piece of the puzzle, Stage 4, is where REM sleep occurs. During this sleep, rapid eye movement occurs, and the person is said to be in a dream state. The brain is more active in this stage of sleep than in Stages 1 & 2. People can easily wake up from this stage of sleep, but doing so results in them being groggy and irritated. A person typically experiences three to five REM periods throughout their sleep time, with the longest REM period occurring right before awakening for the day. If woken up before completing the REM period, a person can experience a period of sleep inertia that heightens the sensation of sleepiness, which can occur for several minutes or even last several hours.
Benefits of Healthy Sleep
The first benefit of sleep that might motivate many people is losing weight. Poor sleep has been shown to have a close correlation with weight gain. People who tend to have short sleep cycles have a greater risk of obesity. In one extensive study, children and adults with shorter sleep durations were 89% and 55% more likely to become obese, respectively, so if you are trying to lose weight, it’s better to get yourself some good quality sleep!
Good sleep quality leads to better concentration and productivity. Sleep, as we already know, is highly important for various cognitive functions. One of the main cognitive functions is concentration. A study of medical interns provided a good example. In that study, the medical interns, in addition to their original work schedule, were given extra work that extended their work time to more than 24 hours, and were about 36% more likely to make serious medical errors.
The quality of sleep is also related to the probability of one developing chronic health issues, such as diabetes, heart disease, stroke and depression, and also suppresses immunity. So, as you can see, good quality sleep is important for maintaining a balanced and healthy lifestyle.