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Why do we sleep?

Roberto León Barriera's picture
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We don’t often think about the purpose of sleep, yet we always feel better and more energized after a good night’s sleep. Studies have shown that we spend about one-third of our lives sleeping. Why is this so? There is no scientific consensus on the specific reason why we need sleep. While the question of exactly why we sleep is difficult to answer, sleep has many benefits. The effects of sleep deprivation can either manifest immediately, such as crashing your car due to excessive tiredness, or can build up with time and lead to chronic conditions. Research shows that sleep deficiency impairs your driving ability as much as being drunk. It is estimated that driver sleepiness is a factor in about 100,000 car accidents a year, and this may cause up to 1,500 deaths a year.

Lack of sleep in the long-term can affect your general health, how well you think and learn, and your mental health. Sleep is involved in the repair of blood vessels and yourheart. Therefore, not getting enough sleep, can increase your risk for chronic heart disease, high blood pressure, and kidney disease. Sleep also maintains the balance between hormones that make you feel hungry (ghrelin) and hormones that make you feel full (leptin). In people who do not sleep enough, the level of ghrelin goes up and the level of leptin goes down, increasing the risk for obesity due to overeating. Sleep is also essential for the maintenance of an adequate immune system. Lack of sleep can affect your ability to fight infections. In fact, experiments in which animals are completely deprived of sleep show that they lose all immune function and die within weeks. Other studies show that sleep deficiency alters brain activity in certain areas, creating difficulty for making decisions and control of emotions. Lack of sleep has been linked to depression and suicide. Research suggests that sleep is also essential for the consolidation of memory and efficient learning. Additionally, lack of sleep affects out alertness and focus, which can impair our acquisition of new information. It is thought that sleep is involved in the strengthening of neural connections that form memories. While it is still not clear how this occurs, many scientists believe it has to do with different patterns of brain activity and brainwaves that occur during sleep. Sleep is particularly important in infants and children. Sleep triggers the release of hormones that promote adequate growth. Infants spend between 13-14 hours sleeping, which has been shown to be essential for adequate brain development.

How much sleep do we need? In general, most adults require 8 hours of sleep, however, sleep requirements vary with each person. Some people may function well with as little as 6 hours of sleep, while others may require more. Despite the importance of sleep, surveys by the National Sleep Foundation reveal that at least 40 million Americans suffer from some type of sleep disorder and 60% of Americans report having difficulty sleeping a few nights a week or more. In addition, more than 40% of adults experience daytime sleepiness severe enough to interfere with their daily activities at least a few days each month. 20% of these adults report sleepiness a few days a week or more. Even more worrying is that 69% of children experience one or more sleep problems a few nights or more during the week. Most of these sleep disorders are not recognized, and therefore are not treated.

What are the most common sleep disorders? The two most common sleep disorders are described below:

  • Insomnia is defined as difficulty falling asleep or staying asleep. This results in too-little sleep orpoor quality sleep. Diagnosis is based on your sleep history or a sleep study, which measures how you sleep and how your body responds to sleep problems. Insomnia can be treated with behavior modification and therapy, medication, or a combination of treatments.
  • Sleep apnea is a disorder in which you have one or more short pauses in breathing for a few seconds to a few minutes, which disrupts your sleep. This is treated with weight reduction (obesity is a risk factor), breathing devices, or surgery.

Sleep researchers suggest various ways that can help improve sleep. These include:

  • Going to bed at the same time every night and wake up at the same time each day
  • Avoid caffeine for four to six hours before bed and minimize daytime use
  • Do not smoke
  • Avoid alcohol and heavy meals before sleep
  • Get regular exercise
  • Minimize noise, light and excessive hot and cold temperatures where you sleep
  • Attempt to go to bed earlier every night for certain period to ensure you get enough sleep

If these tips do not work for you and you continue with sleeping difficulties, it is important you talk to your doctor about your problems. He may help you with different techniques to allow you to fall asleep or refer you to a sleep specialist. It is possible you could be suffering from a sleep disorder that requires treatment.


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