Sleep Fundamentals || Y is for Why Do We Sleep?

From our Sleeping is Fundamental series

Here are some of the top theories explaining why we spend a third of our lives asleep.

why we sleepWhy do we sleep?

It might surprise you to learn that there’s still no hard and fast answer to this question.

Why not? Sleep medicine as a research and clinical focus is still rather young, with key discoveries about sleep occurring mostly in the middle to late 20th century. If sleep researchers don’t know the answer, it’s because there simply hasn’t been enough research to confirm all the theories out there.

What the public may not always understand is that research requires funding, and funding doesn’t happen without a sense of urgent “need to know” as well as the enthusiasm from both the people and the government.

Only until recently has it become clear to everyone in the medical field that sleep is not a passive, secondary process, but rather a dynamic, necessary one for overall health and well being.

Theories about why we sleep

This said, there are some theories which could sensibly explain the purpose of sleep:

We sleep to allow the body to recover from a day’s worth of stress

Sleep provides the body a chance to manage physical and emotional stress accumulated throughout the day. Scientists continue to see distinct links between sleep and recovery for athletes, people experiencing large amounts of emotional stress, even the functionality of the immune system in relation to quantity of sleep.

We sleep to allow the brain to consolidate all the information it has processed during the day

Sleep seems to offer the brain a chance to process everything experienced and learned throughout the day. Consolidating memory in particular (much like “defragmenting” one’s computer) helps keep the brain running efficiently; getting adequate sleep, for this reason, can be linked to better memory health as well and learning performance overall.

We sleep to “recharge the battery”

By being awake for around 16 hours each day, we generate a “sleep drive” not unlike an appetite after having not eaten. This sleep drive pushes us to turn in for the night to recharge and reenergize ourselves.

While a sleep drive might be considered an internal physiological aspect of sleep, it cooperates (or should) with the circadian system, which relies on external time cues like the earth’s light-dark cycles to create a sleep-wake pattern. This explains why you feel so tired during the day after not getting enough consolidated sleep at night.

You need to go into “sleep” mode to maintain optimal health (or, clinically speaking, homeostasis). Sleep deprivation is the often-dangerous consequence of not getting that recharge.

We sleep to deep clean the central nervous system

When we think of waste products in the human body, we’re more apt to consider the digestive and excretory systems, or maybe the skin as an organ which clears waste (through the sweat glands). However, waste management in the body happens literally at the cellular level; each cell has its own cleanup crew to remove toxins.

The brain, made up of billions of cells, must also find a way to remove its waste products. If not, they can lead to neurological conditions like Alzheimer’s disease. Sleep provides the brain with the time needed to do the “dirty work.”

The brain requires sleep to remain “plastic” or flexible to process new stimuli

Neuroplasticity is a term that describes the ability of the brain to makes internal system changes, such as redirecting brain signals through alternative pathways, or cortical remapping. Plasticity can also describe the degree to which the brain can regenerate gray matter or strengthen synaptic connections.

Our brains are thought to be more or less “plastic” at all ages, though it makes sense that children and young adults, who have brains still in development, may actually enjoy more plasticity.

Sleep has been shown to provide opportunities for the brain to do the work of repairing, rebuilding, and remapping.


When will we know for certain why we sleep?

why we sleepThanks to significant gains in neuroscience and the wonderful spotlight pointed at circadian research at the Nobel prize level in 2017, we are learning much more about sleep as a physiological process at a more accelerated rate. Any headlines in the news sharing fresh discoveries about sleep are something to look forward to as researchers continue to demystify this important aspect of human health.


About Tamara Kaye Sellman (621 Articles)

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