What Happens When We Sleep

A man sleeping. When we get good sleep, we're healthier.

Sleep is still a little bit of a mystery. While we don’t know everything about sleep, we think it does several important things.

Sleep helps us conserve energy. When we sleep, our metabolic rate drops. We use about 35 percent less energy than we do when we’re awake.

That doesn’t mean our body is at complete rest when we’re snoozing. For example, our body is busy repairing the damage we did when we were awake. Our cells repair themselves and regrow. They create proteins and hormones and other substances that help us function when our eyes are open.

Our brains are busy too, though not like they are during the day. Short-term memory is converted to long-term memory. Unneeded information is erased.

The brain’s glymphatic system is busy too cleaning out toxic byproducts. This means our brains are ready to go when we wake up and may explain why our minds are clouded after a night of restless sleep.

During sleep, our gray matter is also busy addressing areas that regulate our emotions, which can both support brain function and emotional stability. One area that’s particularly active is our amygdala, which controls our stress response. When we get plenty of sleep, the amygdala reacts normally – but when we miss sleep it’s more likely to overreact to stressful situations.

Our body is managing and making lots of hormones, including those that regulate appetite. These hormones can make us feel hungry or feel full. Unfortunately, when we miss sleep, our bodies produce more of the hormones that encourage hunger and fewer of the ones that encourage fullness.

Our cells also make important immune system components when we sleep, so that it’s easier for us to fight off infection. When we miss sleep, we weaken our immune system.

Getting a good night’s sleep is important for all these reasons and more. When we get seven or eight hours of sleep, we give our bodies and brains a chance to recover and do important work. So make sure you’re getting your zzz’s — sleep is important for our bodies to function and important as a tool to prevent disease.

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