While we have made great progress in understanding the science of sleep, there is still much to be explained. Experts remain uncertain about sleep’s biological purpose, and there are many myths surrounding sleep. We will take a closer look at some of the most common questions about sleep.

How Sleep Works

What Happens When You Sleep?

As you sleep, your brain works to physically repair your body and encode memory . In the process, your brain also flushes out waste that accumulates during your waking hours that may contribute to neurodegenerative diseases.

As this activity happens, your brain cycles through four stages of sleep multiple times a night. The first three stages of sleep are considered non-rapid eye movement (REM) sleep, and the fourth is REM sleep. Each stage of sleep is associated with certain brain wave patterns and physical activities:

  • Stage 1: This non-REM sleep lasts several minutes as you transition from being awake to falling asleep. Your heartbeat, breath, eye movements, and brain waves begin slowing down and your muscles relax.
  • Stage 2: The second stage is also non-REM sleep. Over the course of a night, you spend more time in this stage than other stages. During this stage of light sleep, you experience a lower body temperature and more relaxed muscles. Your heart and breath slow even more.
  • Stage 3: This stage of non-REM sleep is known as deep sleep. In this stage, your heart and breath reach their slowest rates. Your brain waves slow further, and it is difficult to wake you up. In the first half of the night, this stage is longer. In later cycles, it becomes shorter.
  • Stage 4: This stage is REM sleep. About 90 minutes after you first fall asleep, REM sleep begins. During REM, your breath and heart rate speed up. Your eyes move rapidly, hence the name of this stage. A majority of dreams occur during REM sleep. Your brain temporarily paralyzes your muscles, so you do not act out those dreams and hurt yourself.
A normal sleep cycle graph showing the time spent in N1, N2, N3, and REM stages of sleep.

What Is a Circadian Rhythm?

Circadian rhythms are internal cycles that run on a roughly 24-hour schedule, much like the earth’s rotation. Circadian rhythms originate in a part of the brain called the suprachiasmatic nucleus, found in the hypothalamus. These rhythms are most known for regulating your sleep-wake cycle, but they also regulate other important biological processes, such as your core body temperature, appetite, and hormone levels.

Sunlight entrains your circadian rhythm, impacting when you want to sleep and when you want to be awake. When you are exposed to less light, such as in the evening, your melatonin levels rise and you feel sleepy. When you are exposed to more light, melatonin falls and cortisol rises, so you feel alert and awake.

Why Is Sleep So Important?

We spend about a third of our time sleeping. Sleep is as essential to our survival and wellbeing as food and water are. Sleep impacts nearly every aspect of the body, affecting the brain, heart, and lungs, as well as metabolism, mood, and immune system. Physical, emotional, and mental health all depend, in part, on good sleep.

Why Do You Forget Your Dreams When You Wake Up?

Dreams primarily occur during REM sleep. In addition to dreaming, your brain also uses this stage of sleep to make sense of your emotions, process learnings from the day, and decide what to commit to memory. Researchers have identified a particular set of neurons that play a key role in helping your brain forget new information it has deemed unimportant, which may include dreams. These neurons activate during REM sleep.

If you would like to remember more of your dreams, it may help to write them down in a dream journal the moment you wake up.

Sleep Duration

How Much Sleep Do Adults Need?

Most adults need at least seven hours of sleep per night to feel their best. How much you personally need can depend on your activity levels, your genetics, and your physical health. For example, athletes and people who are extremely physically active may need to sleep nine hours. For older adults, sleep needs shorten by an hour to seven to eight hours per night.

Individuals vary in terms of how much sleep they need within the average range. However, if you find you are sleeping significantly more than nine hours or less than seven, it could be a sign of a sleep disorder or underlying health condition.

What Happens If You Don’t Get Enough Sleep?

When you do not get enough sleep, you become sleep deprived. Sleep deprivation can affect you whether you have one night of poor sleep, or suffer from short sleep on a regular basis.

In the short term, sleep deprivation affects your mood, judgment, and ability to focus. While sleep deprived, you might have trouble remembering things and be more prone to make errors at school or work.

In the long term, lack of sleep is associated with chronic health problems like diabetes, high blood pressure, stroke, obesity, depression, and heart and kidney disease. Sleep deficiency also increases your risk for injuries like car accidents.

How Long Should It Take to Fall Asleep?

It should take you about 20 minutes to fall asleep, on average. If falling asleep regularly takes more than 30 minutes, that might be a sign of a sleep disorder like insomnia. Trouble falling asleep could also be the result of poor sleep habits, such as ingesting caffeine late in the day, looking at your smartphone in bed, or following an irregular sleep schedule.

If you still are not asleep after lying in bed for a while, sleep experts recommend getting out of bed. Doing a quiet activity in another room until you feel more tired can help prevent your brain from associating your bed as a place of unrest.

Conversely, consistently falling asleep the moment you get into bed could be a sign of sleep deprivation. Not getting enough sleep on a regular basis can cause excessive tiredness, making you fall asleep quickly.

Sleep Concerns

What Do I Do If I Can’t Fall Asleep?

Many strategies exist to promote falling asleep more quickly. For example, you can practice deep breathing exercises by breathing slowly in and out of your nose and counting each inhale and exhale. You can also try progressive muscle relaxation , a technique that involves sequentially tensing and then relaxing each muscle, from your toes to your head. Music, meditation, and visualization may also help.

If you lie in bed trying to fall asleep and more than 20 minutes pass, get up and go into another room. You want your brain to associate your bed with rest, not tossing and turning. It may help to do something that is quiet and relaxing. You might listen to some soothing music, draw or color, or read a nonfiction book. Avoid using your cellphone, or turning on the TV or computer when you cannot fall asleep.

If you regularly have trouble falling asleep, talk to your doctor. They can advise you on better sleep hygiene or refer you to a specialist to check for a sleep disorder.

What Are Warning Signs of Sleep Deprivation?

The most obvious sign of sleep deprivation is excessive tiredness. Other warning signs of sleep deprivation include:

  • Dozing off while driving, working, watching TV, or reading
  • Difficulty focusing, learning, or problem solving
  • Slower reaction times
  • Trouble remembering things or making decisions
  • Making more mistakes at school or work
  • Behavioral problems in children, such as increased impulsivity, anger, or mood swings
Insufficient sleep increases risks in almost every system of the body.

Do Older Adults Experience More Sleep Problems?

As we age, we sleep less. Whether older adults actually need less sleep, or their brains are not able to regulate sleep to the same extent, is unknown. A reported 1 in 4 older adults experience tiredness that interferes with their daytime plans. Perhaps for these reasons, older adults also nap more often.

Sleep disorders, including insomnia, are more common in old age. As we age, so does our brain, and it is possible that a reduction in gray matter could cause problems with sleep regulation. Alternatively, these brain changes could be the result of sleeping less.

Some sleep problems common in old age are caused by other aspects of aging. Older adults are more likely to have comorbid health conditions that disrupt nighttime sleep, such as chronic pain, depression, or a need to urinate. We also experience a circadian shift in old age, where we naturally tire and wake up earlier.

Why Do I Jerk as I’m Falling Asleep?

If you have ever found yourself jolted awake by a muscle contraction or movement as you were drifting off to sleep, you likely experienced a hypnic jerk. Hypnic jerks are sudden, involuntary muscle jerks that occur in the transition from wakefulness to sleep. They are normal and common. However, if you would like to reduce the chances of these movements happening, it may help to practice stress management and relaxation techniques, limit your use of caffeine and other stimulants, and avoid exercising right before bed.

Why Do I Drool During Sleep?

Drooling is considered a normal part of sleep. Although you produce more saliva during the day, your brain continues producing saliva at night to keep your mouth and throat lubricated and prevent a dry mouth. Back sleepers typically swallow the saliva during their sleep, but side and stomach sleepers may notice some on their pillow in the morning.

Sleep Hygiene

What Is Sleep Hygiene?

Sleep hygiene refers to a set of recommended habits and behaviors designed to promote quality sleep. Educating a person on sleep hygiene is often part of treating insomnia. Sleep hygiene includes:

  • Exercising regularly
  • Keeping stress levels low
  • Following a regular sleep schedule
  • Avoiding or limiting caffeine, nicotine, and alcohol
  • Limiting or avoiding daytime naps
  • Making your bedroom a relaxing environment

Incorporating these practices into your routine may help improve your sleep.

How Can I Get a Better Night’s Sleep?

Your physical, emotional, and mental health all improve with better sleep. Even minor lifestyle changes can lead to more restful sleep. To get a better night’s sleep, you may want to try the following:

  • Follow a Regular Sleep Schedule: Go to bed and wake up at the same time every day. The more consistent your sleep schedule, the easier it will be for you to naturally feel tired and alert at the right times. In older adults, following a daily routine in general is also associated with better sleep.
  • Carefully Choose Foods and Drinks: A sleep-friendly diet includes a variety of foods, with adequate protein and fiber. It also helps to avoid eating anything too spicy or fatty close to bedtime to prevent heartburn or acid reflux from interfering with your sleep. You may want to consider limiting your caffeine and alcohol consumption, too. Both disrupt sleep, especially when ingested in the evening.
  • Get Sun and Exercise: Reinforce your circadian rhythms with plenty of exposure to natural light, especially early in the day. For an extra energy boost, pair your sunlight time with exercise. Daily exercise has been shown to improve sleep.
  • Make Your Bedroom an Oasis: A calm bedroom environment can make it easier to physically relax. Prepare your bedroom environment by keeping it as cool, dark, and quiet as possible to promote sound sleep. It may help to block out light by removing electronics, and using blackout curtains or an eye mask. A white noise machine can help minimize disturbances from outside noises. It is also important to invest in a mattress, pillow, and bedding set that makes you feel comfortable.

What Is the Best Temperature for Sleep?

The ideal bedroom temperature for sleep falls between 65 and 68 degrees Fahrenheit. We tend to sleep more restfully in cooler bedrooms, due to a biological process known as thermoregulation. Throughout the day, our brain keeps our core body temperature within a certain range. In line with our circadian rhythm, our core body temperature begins to dip in the evening and reaches its lowest point in the middle of the night. By keeping our bedroom temperature low, we facilitate this process and encourage more restful sleep.

Do Mattress Type and Cost Really Matter?

Both mattress cost and type can matter when it comes to comfort. A high-quality mattress generally costs between $600 and $2,000. Mattresses that are significantly less expensive are more likely to be made from lower-quality materials or poorly constructed. Mattresses that are more expensive may have extra features and designer elements that do not necessarily translate to better sleep.

The best type of mattress for you is whichever one allows you to sleep soundly at night. It is important to choose a mattress that supports healthy spinal alignment while you sleep, and replace it when that is no longer the case. One study found that when people replace their old mattress with a new one, they report significant improvements in sleep quality and back pain . That study, along with others, also found that medium firm mattresses consistently provided the optimal comfort for most people.

How Long Should I Nap?

Short naps of around 20 minutes can immediately refresh you, relieving sleepiness and improving focus. Longer naps that last over 30 minutes can provide similar benefits for an even longer period of time, but they commonly lead to grogginess upon waking up.

In general, the best time to nap is during the early afternoon. Napping for longer than 30 minutes later in the day, however, can reduce your sleep drive and make it difficult to fall asleep later that night.

Learn more about our Editorial Team

11 Sources

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