Why We Sleep

Why do we sleep?

I have asked myself this question so many times. I have read a few articles over the years but besides the usual stuff, that we need sleep in order for our brain to function (going without sleep will make you depressed and psychotic and eventually will kill you), until recently it wasn’t clear why we need to sleep at all.

Sleep for many can be a risky activity. We are vulnerable when we are asleep. For others, sleep is unproductive, and in a world obsessed with productivity, every single second counts. Still most of us, we spend about a third of our lives asleep. Why do we do it?

There has been quite a lot of research in the past few decades on the subject of sleep. Researchers have found that sleep is key to the brain’s ability to reorganize itself by forming new connections between brain cells (neurons). Our brain never stops changing. This capacity of the brain to change through learning is called plasticity. Brain plasticity and memory are closely connected and sleep deprivation or disruption have been related with Alzheimer’s disease which is the most common form of dementia and affects millions of people worldwide.

Although sleep alone will not be the magic bullet that eradicates dementia, prioritizing sleep is clearly becoming a significant factor for lowering Alzheimer’s disease risk, writes Matthew Walker at his splendid book ‘Why We Sleep: The New Science of Sleep and Dreams’.

Matthew Walker is a sleep scientist. To be more specific, he is a professor of neuroscience and director of the Center for Human Sleep Science at the University of California, Berkeley. In this book he explains why sleep is good both for the brain and the body and also, all the alarmingly bad things that could happen to us if we don’t get enough sleep.

There is a lot to learn in this terrific book about this elegant and symbiotic system that operates in our brains and bodies every night while we are sleeping.

Within the brain, sleep enriches a diversity of functions, including our ability to learn and memorize. Over the years we learned that we need sleep after learning, in order to save the new information and give time to our brain to process memories. During sleep recent memories are transferred from the hippocampus, which acts as a temporary memory indexer, to prefrontal cortex where they consolidated onto long term memories. But we don’t need sleep only after learning, says Matthew Walker. We also need sleep before learning in order to prepare our brains to accept new information. Without enough sleep the brain is miswired, therefore not able to absorb new information.

Sleep is also good for our emotional and mental health. Without sleep the emotional circuits of the brain become hyperactive and irrational. The part of the brain structure, located in the left and right sides of the brain, called amygdala, is the origin of strong emotions, including negative ones, such as anger and rage. Research has shown that in sleep deprived individuals amygdala have been sixty percent more responsive under conditions of lack of sleep and that individuals show an aggravated degree of reactivity. It has been found that that there are significant links between sleep disruption and conditions such as depression, anxiety, PTSD and suicide. Sleep may ultimately be a significant contributor to the prevention of mental illness, writes Matthew Walker.

But sleep is also beneficial and essential for the body. After only a week of deprivation, the blood sugar levels are disrupted so significantly, that you could be classified as diabetic. Sleep reforms the body’s metabolic state by fine-tuning the balance of insulin and circulating glucose. Sleep supports our immune defences by helping preventing infection and even fight malignancy because it is during sleep that the production of pro-inflammatory cytokines (molecules that are released as a response to an infection), takes place. I still remember my grandmother saying ‘sleep helps healing’. It seems that scientific evidence agrees with the popular wisdom.

There is a “silent sleep deprivation epidemic,” …. “the greatest public health challenge we face in the twenty-first century,” argues Matthew Walker. But sleep is not a luxury. It’s not a sign of laziness. It’s an essential biological necessity. It is mother’s Nature best life support system. It’s time to reclaim the right to a good night’s sleep and then “we may remember what it feels like to be truly awake during the day.”

Sleep well.