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What is sleep, and why is it important?

Sleep is elusive for many of us — over 14% of American adults experience trouble falling asleep most days of the week, according to the Centers for Disease Control and Prevention. Yet sleep is one of the body's most impactful processes, and one that we can’t live without. Lack of sleep can have serious short- and long-term effects on your physical and mental health.

Most of us have experienced the “brain fog” associated with a poor night’s sleep. You may struggle to remember simple things or have trouble solving problems or making decisions. You may also find it hard to overcome food cravings the day after an all-nighter, as skimping on sleep can disrupt the hormones that control appetite. The good news is that brain fog and food cravings typically fade away after you get back to a more normal sleep schedule.

But over time, chronic sleep deprivation can have more serious, long-lasting effects. A growing number of studies have linked long-term sleep deficits with significant health problems, among them an increased risk of Alzheimer’s disease, obesity, type 2 diabetes, high blood pressure, heart disease, viral infections, depression, and anxiety.

The stages of sleep

There are many ways to help improve sleep quality and duration to meet the recommended goal of at least seven hours of sleep per night. If you’re trying to get more quality sleep, it can be helpful to understand the different stages of sleep that you pass through during the night.

There are two major types of sleep: REM (rapid eye movement) sleep, and non-REM sleep, also known as quiet sleep. Non-REM sleep has three main stages:

• During stage one, you’re in between being awake and falling asleep. Your sleep at this stage is light and easily interrupted; if someone drops something in the kitchen, it’s likely to wake you up.
• Stage two is considered the first stage of true sleep. Your breathing and your heart rate start to slow, and you become less aware of what’s happening around you.
• And by the time you reach stage three (also known as slow-wave sleep or deep sleep), your muscles are relaxed, your breathing and heart rate are slow and even, and your blood pressure drops. This is the stage where your body renews and repairs itself.

Each sleep cycles lasts about 80 to 100 minutes, with most of us going through four to six sleep cycles per night.

Rapid eye movement (REM) sleep is another part of your body's normal sleep cycle, lasting from just a few minutes to up to half an hour. REM sleep is also known as dreaming sleep, during which your body is paralyzed but your eyes dart back and forth behind closed eyelids. Your blood pressure increases, and your heart rate and breathing speed up. REM sleep is important for processing and consolidating new information you’ve learned. (And people who don’t get enough may be at a greater risk for dementia, according to a study published in the journal Neurology.) This is why people often recommend that you "sleep on it" when you're dealing with a problem.

Sleep hygiene: Habits for better rest

Some causes of poor-quality sleep take time, patience, and may require professional help. For example, some medical conditions can impact or disrupt your sleep, including:

• sleep apnea (a condition in which breathing temporarily stops or becomes shallower many times each night, causing the sleeper to rouse, if not completely awaken)
• insomnia (trouble falling asleep, unwelcome awakenings, or fitful sleep)
• narcolepsy (a disorder affecting the regulation of the sleep/wake cycle)
• other medical conditions including chronic pain, diabetes, heart disease, acid reflux, thyroid disease, and some brain and nerve disorders.

Our schedules and habits can also be to blame. Not all of these disruptors can be eliminated or solved; people who work an evening or night shift (health care workers, police officers, security guards, and transit workers, for example) may not be able to change their schedules to better accommodate a sleep cycle that’s aligned with their bodies’ natural sleep/wake cycles. For these shift workers, the best options may be more subtle, like getting your family on board with your sleep schedules, negotiating a new start or end time to your workday, or investing in a light therapy lamp.

But all of us can benefit from better sleep hygiene. Sleep hygiene is a set of practices and routines that help you get better sleep.

Some tips include:

• adhering to a regular sleep schedule (even on the weekends)
• turning the temperature down in the bedroom
• using dark curtains or eyeshades to keep daylight out
• running a fan to help block external noise
• using the bedroom only for sleeping or sex
• keeping the bedroom free of distractions like the computer, television, or your phone
• relaxation techniques such as meditation, guided imagery, deep breathing exercises, and progressive muscle relaxation (alternately tensing and releasing muscles) to counter anxiety and racing thoughts
• avoiding exercising within two hours of bedtime
• avoiding long or late afternoon naps
• eating dinner at least three hours before bedtime, and avoiding alcohol in the evening.

What to do when you can't sleep

If you try all of the above and still can’t sleep, get out of bed and do something else, like read a book or listen to a non-stimulating podcast. And if sleep still eludes you, talk to your doctor. They can identify causes and recommend solutions — from medications for heartburn to cognitive behavioral therapy for insomnia (CBT-i), which includes strategies like setting regular wake times and using relaxation techniques.