2.6: The Importance of Sleep

Although Sleep is not included as an important behavior in either the Physical Activity Guidelines for Americans (2nd edition) or the WHO Guidelines on Physical Activity and Sedentary Behaviour, Sleep is addressed as an important health outcome when considering the impact of physical activity and sedentary behavior. Along with nutrition and exercise, sleep is one of the three pillars of a healthy lifestyle. Healthy sleep improves your health and quality of life in a variety of ways.

Sleep is an important part of your daily routine—you spend about one-third of your time doing it. It is estimated that about 1 in 3 adults, and even more adolescents, don’t get enough sleep, which can affect their health and well-being. People who don’t get enough sleep are more likely to have health problems like obesity, diabetes, heart disease, stroke, dementia, and cancer. They’re also more likely to have trouble at work or school. In addition, about 100,000 motor vehicle crashes every year in the United States are related to drowsy driving. It is recognized that improving sleep habits and sleep environments can help people stay healthy and safe. Thus, is is not surprising that one of the goals of Healthy People 2030 is to improve health, productivity, well-being, quality of life, and safety by helping people get enough sleep.

Getting good sleep is not just about the quantity of sleep, but also the quality of sleep. Healthy sleep requires adequate duration, good quality, appropriate timing and regularity, and the absence of sleep disturbances or disorders.

Recommended Sleep Quantity

The American Academy of Sleep Medicine recommends that adults should sleep 7 hours or more per night on a regular basis to promote optimal health.

Table \(\PageIndex{1}\) : How much sleep do I need?^[7]

Age Group	Recommended Hours of Sleep Per Day
0–3 months	14–17 hours (National Sleep Foundation) No recommendation (American Academy of Sleep Medicine)
4–12 months	12–16 hours per 24 hours (including naps)
1–2 years	11–14 hours per 24 hours (including naps)
3–5 years	10–13 hours per 24 hours (including naps)
6–12 years	9–12 hours per 24 hours
13–18 years	8–10 hours per 24 hours
18–60 years	7 or more hours per night
61–64 years	7–9 hours
65 years and older	7–8 hours

Healthy Sleep Habits

Tips for healthy sleep habits^[8] include:

• Keep a consistent sleep schedule. Get up at the same time every day, even on weekends or during vacations.
• Set a bedtime that is early enough for you to get at least 7-8 hours of sleep.
• Don’t go to bed unless you are sleepy.
• If you don’t fall asleep after 20 minutes, get out of bed. Go do a quiet activity without a lot of light exposure. It is especially important to not get on electronics.
• Establish a relaxing bedtime routine.
• Use your bed only for sleep and sex.
• Have a warm shower/bath or a cup of herbal tea
• Make your bedroom quiet and relaxing. Keep the room at a comfortable, cool temperature.
• Do your best to avoid having disruptive pets, children, partners sleep with you
• Make sure your room is pitch black or use a sleep mask over your eyes
• Limit exposure to bright light in the evenings.
• Turn off electronic devices at least 30 minutes before bedtime.
• Don’t eat a large meal before bedtime. If you are hungry at night, eat a light, healthy snack.
• Exercise regularly and maintain a healthy diet.
  • The time we spend doing moderate to vigorous activity throughout or day will benefit our sleep. Strong evidence demonstrates that moderate-to-vigorous physical activity improves the quality of sleep in adults. It does so by reducing the length of time it takes to go to sleep and reducing the time one is awake after going to sleep and before rising in the morning. It also can increase the time in deep sleep and reduce daytime sleepiness. The improvements in sleep with regular physical activity are also reported by people with insomnia and obstructive sleep apnea. In children, the more they are sedentary the lower their sleep duration.
• Avoid consuming caffeine in the afternoon or evening.
• Avoid consuming alcohol before bedtime.
• Reduce your fluid intake before bedtime.

Understanding Sleep

The National Sleep Foundation provides helpful information about the basics of sleep including understanding circadian rhythms and the sleep cycle^[9].

Major advances in sleep science have occurred over the past half-century since the discovery of rapid eye movement (REM) sleep in 1953^[10].

Circadian Rhythm

Have you heard the term circadian rhythm? Circadian means “recurring naturally on a twenty-four-hour cycle, even in the absence of light fluctuations,” it is sometimes called the “body clock.” When we talk about circadian rhythms, it’s mostly in relation to sleep.

Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle. Your circadian rhythm is regulated by your bodies biological clock, which is an organisms’ natural timing device. The master clock in the brain is a group of about 20,000 nerve cells (neurons) and coordinates all the biological clocks in a living thing, keeping the clocks in sync. Without the right signals from your body’s internal master clock, you might not fall asleep, have fragmented or sleep poorly, or wake up too early and not be able to fall back to sleep.

Your body’s biological clock produces circadian rhythms and regulates the timing of things in your body, like when you want to sleep or eat. Your circadian rhythm can influence important functions in your body such as releasing hormones, your eating habits, and your body temperature. For example, your digestive system produces proteins to make sure you eat on schedule, and the endocrine system regulates hormones to match your energy expenditures during the day.

Although natural factors in your body produce circadian rhythms, the environment, such as daylight, exercise, and temperature, also affect them. For example if you experience jet lag or change to working a night shift it could impact your light-dark cycle. The light from electronic devices at night can also confuse your biological clock and impact your circadian rhythm.

Sleep Stages (Sleep Cycle)

In 1953 there was a breakthrough in sleep science, this is when our understanding of what happens during sleep drastically changed. Prior to the 1950’s it was thought that our brains just shutdown when we slept, however in the 19050’s scientist learned that our brains do not shutdown, rather they cycle through several different stages of sleep. Dr. Nathaniel Kleitman was an American physiologist known as the Father of American sleep research, he and his students discovered what we now call REM sleep, or rapid eye movement sleep. Prior to the incredible work produced by Kleitman, it was thought that the brain and body were in a completely inactive state during sleep. It was discovered that over the course of one night, your body goes through the sleep stages every 90 minutes or so. Sleep stages last for different periods of time depending on the age of the sleeper, but generally speaking non-REM cycles are longer in the beginning of the night while REM cycles are longer later in the night.

There are two types of sleep: Non-REM and REM sleep. Non-REM sleep is furthered divided into three stages (stage 1, stage 2, stage 3) where distinct brain activity occurs. REM sleep involves more brain activity than Non-REM and is considered a more “wakeful” state, as your heart rate and blood pressure increase to levels close to what you experience when you are awake. While all sleep stages are important, Stage 3 and REM sleep have unique benefits. One to two hours of Stage 3 deep sleep per night will keep the average adult feeling restored and healthy. If you’re regularly waking up tired, it could be that you’re not spending enough time in that deep sleep phase. Meanwhile, REM sleep helps your brain consolidate new information and maintain your mood – both critical for daily life. Talk to your health care provider if you feel you are not getting the restful sleep that you need.

The Four Sleep Stages (cycles)

Stage 1 (Non-REM)
Stage 1 of the sleep cycle is the lightest phase of sleep and generally lasts about seven minutes. The sleeper is somewhat alert and can be woken up easily. During this stage, the heartbeat and breathing slow down while muscles begin to relax. The brain produces alpha and theta waves.

Stage 2 (Non-REM)
In Stage 2, the brain creates brief bursts of electrical activity known as “sleep spindles” that create a distinct sawtooth pattern on recordings of brain activity. Eventually, the waves continue to slow down. Stage 2 is still considered a light phase of sleep, but the sleeper is less likely to be awakened. Heart rate and breathing slow down even more, and the body temperature drops. This stage lasts around 25 minutes.

Stage 3 (Non-REM)
This stage represents the body falling into a deep sleep, where slow wave sleep occurs. The brain produces slower delta waves, and there’s no eye movement or muscle activity from the sleeper. As the brain produces even more delta waves, the sleeper enters an important restorative sleep stage from which it’s difficult to be awakened. This phase of deep sleep is what helps you feel refreshed in the morning. It’s also the phase in which your body repairs muscle and tissue, encourages growth and development, and improves immune function.

Stage 4 – REM Sleep
About 90 minutes after falling asleep, your body enters REM sleep, which stands for Rapid Eye Movement sleep and is named so for the way your eyes quickly move back and forth behind your eyelids. REM sleep is thought to play a role in central nervous system development in infants, which might explain why infants need more REM sleep than adults. This sleep pattern is characterized by dreaming, since your brain is very active during this stage. Physically, your body experiences faster and irregular breathing, increased heart rate, and increased blood pressure; however, your arm and leg muscles become temporarily paralyzed, stopping you from acting out your dreams. REM sleep increases with each new sleep cycle, starting at about ten minutes during the first cycle and lasting up to an hour in the final cycle. Stage 4 is the last stage before the cycle repeats. REM sleep is critical for learning, memory, daytime concentration, and your mood. REM sleep plays a significant role in helping your brain consolidate and process new information and then retain the information in your long-term memory. Without REM sleep, your immune system could be weakened, you may experience pain more deeply, poor memory, mood dysfunction, less ability to focus, and the growth of new healthy cells and tissue in the body might be blocked. Poor REM sleep may be due to sleep disorders such as insomnia or obstructive sleep apnea, which causes you to wake during the night.

Sleep Disorders

Quality of sleep is impacted by several types of sleep disorders^[11] including insomnia, hypersomnias (or excessive sleep), circadian rhythm sleep-wake disorders, parasomnias (or sleep events), sleep-related breathing disorders, or sleep-related movement disorders. Sleep disorders, like sleep apnea, negatively affect people’s health and safety, and many adults who have a sleep disorder don’t get the treatment they need.

Raising awareness about sleep disorders can help people recognize symptoms and get the help they need. The American Academy of Sleep Medicine (AASM) provides extensive information and resources about sleep disorders to help inform you about the different types, symptoms, and treatments.

Challenge: Understand Your Sleep

A sleep diary is a useful way to track your sleep at home by recording when you went to bed, woke during the night, and woke in the morning. It is helpful to also track the time of day when you exercise, nap, or take a medication, and when you have caffeine or alcohol.

A sleep diary will help you understand your sleep pattern and how much sleep you’re getting. It also will show how often you have disrupted sleep. It may also will help you note certain activities that can affect your sleep.

Keeping a sleep diary is very helpful for communicating with your doctor about your sleep.

Use the AASM Sleep Diary