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Key takeaways
Sleep plays a critical role in physical and mental health. Not getting enough sleep increases the risk of obesity, diabetes, heart disease, stroke, and depression.
Circadian rhythms and sleep-wake homeostasis regulate sleep, which consists of REM and non-REM stages. Sleep supports immune system performance and memory consolidation.
The Centers for Disease Control and Prevention (CDC) recommends different amounts of sleep for different age groups, emphasizing that quality and quantity of sleep are important for health.
Maintaining good sleep hygiene, such as keeping a consistent sleep schedule and creating a comfortable sleep environment, can improve sleep quality and overall health.
For many, the best part of the day is getting into bed for a good night’s sleep. Some people even think of sleep as a guilty pleasure. The good news, though, is that sleep is not a luxury—it’s a necessity. Getting enough sleep, in terms of quantity and quality, is important for the body. Sleep is critical for both physical and mental health, and not getting enough sleep can increase the risk for many conditions, such as obesity, diabetes, heart disease, and depression. The American Academy of Sleep Medicine issued a statement saying that sleep is essential to health. Continue reading to learn more about why we need sleep.
The science behind sleep
What happens when we sleep? The short answer: a lot! Let’s dive in.
Two internal mechanisms work together to regulate sleep and wake cycles:
- Circadian rhythms are in charge of many functions, such as temperature, metabolism, and hormones. These rhythms make you feel tired at night and help you wake up in the morning. The body’s biological clock controls most circadian rhythms.
- Sleep-wake homeostasis reminds the body when it is time to sleep. It knows when you need to sleep longer and more deeply. This can be affected by medical conditions, medicines you take, stress, diet, sleep environment, and light exposure.
The two types of sleep are rapid eye movement (REM) sleep and non-rapid eye movement (non-REM) sleep. The body goes through all stages of both types of sleep each night, with longer and deeper REM periods toward the morning hours.
- Stage 1 non-REM sleep is when you go from being awake to falling asleep. You are in a light sleep. Your heartbeat, breathing, and eye movements slow down, and muscles relax as brain waves slow down.
- Stage 2 non-REM sleep is a period of light sleep before you enter into a deeper sleep. The heartbeat and breathing remain slower, muscles relax more, body temperature drops, and your eyes stop moving. Brain wave activity slows, but there are quick bursts of electrical activity. This is the sleep cycle where you spend the most time throughout the night.
- Stage 3 non-REM sleep is a deep sleep that helps you feel refreshed when you wake up. Your heartbeat and breathing are at their lowest levels. Brain waves are even slower. It is difficult to wake up during this stage.
- REM sleep starts about 90 minutes after you first fall asleep. Your eyes move back and forth behind closed eyelids. Brain wave activity is more similar to that when you are awake. Breathing becomes faster and irregular, and heart rate and blood pressure increase. This stage is where most of your dreaming happens, and your arm and leg muscles are temporarily paralyzed, keeping you from “acting out your dreams.” As you get older, you spend less time in REM sleep.
How much sleep do I need?
The Centers for Disease Control and Prevention (CDC) outlines sleep requirements by age.
To summarize sleep requirements for older children and adults:
- Adults ages 18 to 60 years old need at least 7 hours of sleep per night
- Adults ages 61-64 years old need 7 to 9 hours of sleep per night
- Adults age 65 years and older need 7 to 8 hours of sleep per night
- Teenagers (13-18 years old) need 8 to 10 hours of sleep in 24 hours
- School-age children (6-12 years old) need 9 to 12 hours of sleep in 24 hours
Equally as important as sleep quantity is sleep quality. If you are sleeping 8 hours a night but waking up every hour, that is not quality sleep. You may be experiencing poor sleep quality if you:
- Wake up not feeling rested after a full night of sleep
- Wake up throughout the night
- Have symptoms of sleep disorder like snoring, gasping, or choking
To improve sleep quality, follow the sleep hygiene tips outlined in the section below called How to improve sleep quality—and see a healthcare provider if you have symptoms of a sleep disorder.
Physical benefits of sleep
People who do not get enough sleep are at higher risk for conditions such as obesity, diabetes, high blood pressure, high cholesterol, heart disease, stroke, and depression. And many of these conditions become a cycle with sleep—for example, lack of sleep may contribute to diabetes, and then when you have diabetes, you have trouble sleeping.
Getting enough sleep can provide you with many physical benefits.
Immunity
We depend on our immune systems to prevent illness, as well as fight illness when we are sick. Sleep helps support the immune system. Getting enough quality sleep helps the immune system. While sleeping, the immune system works behind the scenes to remember how to recognize and react to antigens (substances that cause an immune response). Sleep is one of many factors that help the body respond better to vaccines.
On the other hand, people with sleep problems like insomnia or sleep apnea may have an immune system that does not function as well.
Weight management
People who sleep less than seven hours a night on a regular basis are more likely to have obesity and a higher body mass index (BMI). Lower quantity and quality of sleep often lead to increased caloric intake, often with foods that are high in fat and carbohydrates.
Studies show that better sleep quantity and quality help people lose weight.
Heart health, including blood pressure
Studies show that not getting enough sleep can affect the heart and is associated with stroke, heart disease, and high blood pressure.
However, sleeping 9 hours or more per night may also be associated with high blood pressure and heart disease.
People with sleep disturbances, such as sleep apnea, are more likely to have a stroke, as well as a worse outcome after having a stroke.
Sleep is so important to heart health that the American Heart Association has added sleep to its cardiovascular health checklist, noting that adults should sleep between seven and nine hours per night.
Experts at Columbia University Irving Medical Center state that the heart benefits from consistent sleep, citing studies that found older adults with the most irregular sleep schedules were almost twice as likely to develop heart disease compared to people with regular sleep patterns. Keeping a regular schedule of going to sleep and waking up around the same time every day can help with heart rate, blood pressure, and other heart functions.
Blood sugar metabolism and diabetes
Researchers report that not sleeping enough (in terms of both quantity and quality) or sleeping too much (more than 9 hours per night) can be related to insulin resistance—although they note that the relationship between Type 2 diabetes and not sleeping enough is much better understood than sleeping too much.
One study analyzed 36 clinical trials with over one million participants and found that people with poor sleep quality (as well as those with sleep apnea or who were shift workers, both associated with sleep disturbances) had a similar risk of diabetes to people with risk factors such as family history, being overweight, and not being physically active.
Sleeping better may help control blood sugar levels. The CDC reminds patients that proper sleep helps with diabetes management as well as mood and energy levels—noting that too little sleep negatively affects every area of diabetes management, including how much and what types of foods you eat, insulin response, and mental health.
Athletic performance
Studies show that when athletes do not get adequate sleep, there is a negative effect on physical and mental performance, risk of injury (and recovery), and medical and mental health.
But, when they get enough quality sleep, athletes have improved strength, speed, reaction time, cognitive performance, and mental health.
Helps inflammation
Inflammation can contribute to many conditions, including:
- Autoimmune diseases such as rheumatoid arthritis
- Heart disease
- High blood pressure
- Inflammatory bowel disease
- Asthma and other lung conditions
- Depression and other mental health conditions
- Type 2 diabetes
- Parkinson’s disease
- Certain types of cancer
Sleep deprivation is associated with inflammation, and experts note that getting enough quality sleep reduces inflammation. Studies note the “importance of adults consistently sleeping seven to eight hours a day to help prevent inflammation and disease, especially for those with underlying medical conditions.”
Mental health and sleep
The National Institutes of Health (NIH) reports that people who do not get enough sleep have trouble controlling emotions and behavior. Sleep deficiency is linked to anxiety, depression, suicide, and risky behavior. Children and teenagers who do not get enough sleep may have difficulty getting along with their peers, feel angry or impulsive, have mood swings, and feel sad or depressed.
About who have insomnia (trouble sleeping) experience depression—and up to 80% of people with depression experience insomnia.
The National Alliance on Mental Illness (NAMI) recommends that “everyone experiencing depression should work to improve and regulate their sleep because there are only benefits to be had.”
And researchers at UC Berkeley found that deep sleep can decrease anxiety overnight. They stress the importance of getting deep sleep every night as a natural remedy for anxiety.
Sleep and productivity
Although you may be reluctant to stop working or checking tasks off your list to get some zzz’s, sleep is actually essential for productivity. The NIH reports that sleep deficiency has played a role in human errors linked to major tragic accidents such as plane crashes and nuclear reactor meltdowns, noting that research shows that getting enough quality sleep (remember quantity and quality!) is “vital for mental health, physical health, quality of life, and safety.”
Professors at MIT found that better sleep habits (consistency, quality, and quantity) were associated with better grades. They concluded that this study was a “strong indication” that sleep “really, really matters.”
The Chronobiology and Sleep Institute at the University of Pennsylvania Perelman School of Medicine reports that researchers have found that sleep helps students perform well, learn, memorize, retain, recall, and apply knowledge to solve problems creatively—and all these help test scores, too.
How to improve sleep quality
Good sleep hygiene can help you sleep better. The CDC offers some helpful tips on getting quality sleep:
- Maintain a consistent sleep schedule. Go to sleep and wake up at about the same time every day, even on weekends.
- Keep the bedroom cool (experts recommend 65 degrees), dark, quiet, and relaxing.
- Keep electronic devices out of the bedroom—not only the TV and computer but smartphones too.
- Take some time to relax before bed. Establish a routine like taking a shower and reading, then get in bed when you are tired and ready to nod off.
- Exercise during the day. Ask your healthcare provider about safe and appropriate exercise.
- Avoid caffeine in the afternoon and evening, and avoid alcohol at night.
- Avoid smoking and vaping.
- Don’t eat large meals late at night. Doing so can cause heartburn and increase blood sugar levels while you sleep.
- If you nap, nap early. Napping after 3:00 p.m. can affect your nighttime sleep.
If you have trouble sleeping, talk to your doctor.
The bottom line—why do we sleep?
Sleep is not just a pleasant time to relax and unwind, it’s absolutely necessary for your body to recover and get stronger physically and mentally.
Not getting enough sleep, in terms of both quality and quantity, can affect your health in many ways, increasing the risk for conditions such as diabetes, heart disease, obesity, and depression.
Making the effort to consistently get a good night’s rest with the right amount of quality sleep can work wonders for your mental and physical health. What steps can you take today to improve your sleep quality and overall health?
