Sleep is a vital nightly “tune-up” for brain and body health and wellbeing.

During sleep, the human body seems quiet, but at a molecular, chemical, and cellular level, the body is hard at work.

Over the time you are awake, your body uses resources that only adequate sleep can replace.

Essential sleep stages must cycle a certain number of times (requiring a certain number of hours of sleep) for peak performance the following day.

Sleep Matters 

A sleeping person looks like a person at complete rest, but it’s deceptive. Numerous critical bodily functions are hard at work, repairing, replacing, and replenishing, and can only take place when you sleep for a certain number of hours. Too little or too much sleep has a profound effect on your physical health. While most of us know that a restful night’s sleep gives us more energy during the day, there are many other systems at work during sleep time. During sleep, the immune system fights existing threats, removes harmful substances, and refortifies itself. Immune health is essential to lowering the risk of acute and chronic conditions including colds and flu, as well as, diabetes, excess weight, arthritis, metabolic syndrome, heart disease, and cancer. Meeting your sleep quota is also critical to your mental and emotional health and stability to learn and remember, to be more focused and clear, and to be less depressed and anxious. Sleep also gives your body time to repair, replace, and fortify your cells, immune system, and other bodily functions. Unfortunately, two-thirds of adults across all developed nations don’t get the recommended amount of sleep that they need each night.

What exactly is sleep?

When you are asleep, you can’t protect or provide for yourself or your family. So why do we do it? Is it an evolutionary mistake? Sleep is not what it appears to be—a passive, dormant condition of our human lives. The American Sleep Association defines sleep as a dynamic activity that is controlled by nerve-signaling chemicals (neurotransmitters) to your nerve cells (neurons). The National Institute of Health reminds us that sleep is “as essential to survival as food and water.” The neurons in your brain stem and spinal cord produce nerve impulses that tell your brain to produce neurotransmitters that switch on to help you to be awake and alert. When it is time to sleep, different neurons and chemicals are released to make you sleepy (such as melatonin).

What happens when you sleep?

Scientists have worked, and continue to work, long and hard to dissect what occurs in the brain and body of a person who sleeps. What looks on the surface like one thing happening—sleep—is a complex process involving your brain and body. An adult typically needs between seven and nine hours of sleep each night to wake up in the best shape—physically, emotionally, and mentally—each day. It is during the deepest phases of sleep that all your trillions of cells get busy replenishing your muscles, repairing and re-growing tissues, and restoring energy supplies to your brain and body. This includes the hormones ghrelin and leptin, which affect and regulate feelings of hunger and fullness. This is one of the reasons we tend to overeat when we are sleep-deprived.

A healthy way to be brain-washed:

Your brain helps you to consolidate memories and cleanses your body of toxins during sleep. That grey matter is the command center of your body, but without adequate sleep, your brain can’t “tell” your body what it needs to do. Almost every organ system and function of your body rely on signals from your brain—immune system, metabolism, appetite, digestive health, heart health, and so on.

These signals tell your body to regulate, balance, and repair your body. Your immune system refortifies itself to fight diseases and to prevent infection and illness. Your hormones that affect and regulate your appetite, body weight, and impulsivity are modified and rebalanced. Your digestive system replenishes its levels of healthy bacteria and repairs your gut lining. Your blood pressure lowers, and your muscle tissues repair. In other words, your brain and body get a full “tune-up” every time you get a good night of sleep.

How much sleep do I need?

The amount of sleep you need for peak physical, mental, and emotional performance ranges from seven to nine hours each night. Some adults seem to be able to get by on less sleep, but they are a rare exception to this rule. Why do you need this much sleep? Still want more details? The National Sleep Foundation offers a chart that gives recommendations for sleep at various ages.

How much sleep do I need?

Neuroscientists have determined that there are five stages of sleep that ideally repeatedly cycle over the course of nightly (or daily) sleep. Stage 1 is light sleep where your muscles begin to relax, and your body temperature falls. Stage 2 is deeper than stage 1, and your brain waves begin to slow down. Stage 3 and 4 are progressively deeper phases of sleep with your brain waves slowing more and no dreaming. These stages occur around 20 to 30 minutes after we fall asleep, and this is the most restful part of your sleep. Interestingly, some research shows that these stages of deeper, restful sleep decrease as we age. REM sleep usually begins around 80 to 100 minutes after first falling asleep, and this is where the magic happens. Your brain progressively signals your body’s muscles to relax as you move through these stages (a good thing, because you don’t want to act out your dreams).

During REM sleep, your muscles are deeply relaxed. It’s during stages 3, 4, and REM sleep that your brain organizes, consolidates, and stores your memories. Your brain weighs the information you experienced during awake hours and decides what to keep and discard. However, sleep doesn’t just go from stage 1 to REM one time. Sleep stages are cyclical and occur in repeating cycles. The first cycle is around 70 to 90 minutes, and then, cycles slow to around 90 to 110 minutes. During these cycles, you will go back through light, deep, and REM sleep. Cycles or REM sleep are longer at the later hours of your sleep time. Babies spend most of their time in REM sleep because their brains are still developing. A toddler’s REM sleep drops to around 20 percent, and as we age REM sleep can drop to 15 percent or lower.

In Part 2 of this article, we’ll discuss the steps you can take to get the most from your sleep time.