Why do we sleep?

Feb 16, 2020

Why do we sleep?

Feb 16, 2020

The truth is that no one truly knows the main reason we sleep. However, the structures involved in, stages of and chemical processes behind sleep are becoming increasingly more understood with links to several significant processes being shown throughout research.

While many people think of sleep as a time of rest (which it is physically), the brain can actually be very active throughout certain stages of sleep. This activity is believed to affect the internal part of the brain more than anywhere else but does have effects on other areas such as the endocrine and immune systems. Within the brain, strengthening connections between different cells for newly learned movements and activities (plasticity), consolidating memories and ‘clearing out’ the toxins of built up waste produced from the days brain activity are a few of the important things that have been shown to be happen during sleep.

Our desire/need for sleep is driven internally via our own 24-hour rhythms (circadian rhythms) involving multiple neurotransmitters (chemicals) released in our body throughout the day that can be affected by external factors – predominantly daylight. Our body also goes through a process called sleep-wake homeostasis whereby it maintains a balance between the two states. For example, if we have been awake for a long time, our bodies will feedback to itself and stimulate more neurotransmitter to stimulate sleepiness.

How does sleep affect my pain and how does my pain affect my sleep?

There is plenty of evidence to show the relationship between sleep and pain in adults, adolescents and children. Lack of sleep will have a generically detrimental effect on pain and better sleep proves to have a more positive effect on pain. However, there are also several factors to consider – length of sleep, regularity of sleep disturbance and perceived quality of sleep to name a few.

Lack of sleep can increase the sensitivity of the nervous system and this can cause increased perception of sensory input such as the perception of acute and chronic pain.

Chronic pain has been extensively researched and having a chronic painful physical condition has been shown to be a major contributor to worsening of pre-existing insomnia and to those developing it. Positively, more acute conditions such as early post-surgical patients have been shown to have improved speed and recovery with reduced pain with procedures such as total knee replacements when having better sleep.

However, sleep can affect people in other ways too with studies showing those in chronic pain (of varied natures including headaches, arthritis and sickle cell disease) have high correlations of depressive symptoms alongside low mood, a reduced daily ability to function and health-related quality of life when reporting a high level of sleep disturbance, which can loop back to a higher level of perceived pain again.

How much should I sleep and how do I have better sleep?

The underlying fact is that here is no magic number for the number of hours we should sleep as it is proposed that different functions of our body may be best with varied amounts of sleep (a different dose-response relationship). Also, everyone has different circadian rhythms and internal drivers such as cortisol, adrenaline and serotonin levels to each other and they will vary on different days. So, to get “the best sleep” is an impossible thing to answer. The best guess from experts is that 7-9 hours is recommended for 18-64 year olds and 7-8 for those older than that, with those under 18 requiring more again likely due to state of maturation and that growth hormone is often released at night.

Despite this, there are some tips to improve aspects that lead to improved quality of sleep:

  • Avoid caffeine from late afternoon (this interact with neurotransmitters making you less tired)
  • Avoid alcohol before bed
  • Exercise daily but not immediately before bed (30mins is advised – decreases stress hormones and tires muscles, increasing the bodies need for sleep)
  • Use your bed exclusively for bedtime activities (not screens such as phones, laptops and TV’s)
  • Avoid external lights in the area you sleep
  • Maintain a routine before bed to prepare yourself for sleep including a consistent time

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