Sleep – it’s something that we all need, and also something that many of us don’t get enough of! But have you ever wondered why we sleep, and why it is so important to us? We’ve tried to track down some of the science behind why we sleep.
Sleep occurs in cycles, and divided into two types of sleep – non-REM sleep, and REM sleep. There are four stages of sleep within non-REM sleep.
The first stage of non-REM sleep is where we are in a light sleep, being neither fully awake nor fully asleep. A person can be easily woken up in this stage of sleep. Stage two, or true sleep, last for about twenty minutes and, in this stage, a person’s heart rate and respiration slows down. This stages accounts for the largest portion of sleep. Stages three and four are stages of deep sleep. Stage three sees the brain producing delta waves, a pattern that is large and slow. A person’s breathing and heart rate is at its lowest during this stage. Stage four is represented by a rhythmic breathing pattern and limited muscle activity. If a person is awakened during this stage, they cannot immediately adjust and may feel groggy or disorientated for several minutes after awakening.
The first period of REM or rapid eye movement sleep starts anywhere from 70 to 90 minutes after falling asleep. The average person will have anywhere from three to five episodes of REM sleep per night. During REM sleep, the brain is very active, sometimes even more so than when a person is awake! REM sleep is when most dreaming happens. The eyes move around (which is where the name comes from), and the respiration rate and blood pressure rises. Despite this, the body is essentially paralysed, so that a person cannot act out their dreams. Once the REM sleep is over, the whole sleep cycle begins again.
Sleep is essential because it helps to maintain cognitive skills and also plays an important role in brain development. If a person does not get enough sleep, there will be serious effects on the brain and its ability to function. After just one night without sleep, concentration is difficult, the attention span shortens, and a person may feel irritable, grumpy, groggy, or forgetful. If a person continually gets less sleep than they need, the area of the brain that controls language, memory, planning, and the sense of time becomes severely affected.
People that don’t get enough sleep also have trouble responding to rapidly changing situations and have trouble making rational judgments. If people are in a continual state of wakefulness, they can hallucinate and lose their grip on reality. In fact, if sleep is withheld for a long enough period of time, it can actually be fatal.
Lack of sleep not only affects a person’s cognitive functioning but also their emotional and physical health. Disorders such as sleep apnea have been linked to stress and high blood pressure. Lack of sleep has also been linked to obesity because the chemicals and hormones that play an important role in controlling appetite and weight gain are released during sleep.
As well, children secrete growth hormone during their sleep, which is important for their development. Chemicals that are needed by the immune system are also secreted during sleep, so a lack of sleep can actually result in a person becoming more prone to disease.
There are no hard and fast rules about how much sleep a person needs to function optimally as each person is different. The amount of sleep necessary could be anywhere between five and eleven hours, with just under eight hours being the average. The amount of sleep a person needs seems to decrease with age. For example, a newborn may sleep for twenty hours a day, while elderly people may need only six or seven hours a day.
A person has sleep patterns, which vary according to their sleep hygiene, how much physical activity they undertake, and how healthy the person is both physically and mentally. The term “sleep hygiene” refers to how we choose to sleep and it is vital to a person’s health and fitness. Because sleep is practiced according to a circadian rhythm, a person’s sleep patterns are at their best if bedtimes and the amount of sleep are consistent. If a person delays their normal bedtime or wakes up earlier than usual, this will affect a person’s performance the next day, both mentally and physically.