Deep Sleep and the Impact of Delta Waves

woman being hooked up to sleep study machinery


A delta wave is a type of high amplitude brain wave found in humans that is associated with deep sleep. Delta waves have a frequency from one to three hertz (Hz) and are measured using an electroencephalogram (EEG).

These brain waves are thought to emerge from the thalamus and are generally associated with slow-wave sleep (which begins during the third stage of sleep.) This period of time during which delta waves occur is often known as deep sleep.

How Delta Waves Are Measured During Deep Sleep

Delta waves were first identified and described in the early 1900s after the invention of the EEG allowed researchers to look at brain activity during sleep. During sleep, the brain cycles through a number of different stages differentiated from each other by the brain activity that occurs during each stage.

During the initial stages of sleep, people are still awake and somewhat alert. At this point, the quick and small beta waves are produced. Eventually, the brain begins to slow down and slower waves known as alpha waves can be observed with an EEG. Once asleep, the stages of sleep can begin:

  • Stage 1 (N1) is light sleep, typically beginning soon after getting into bed and lasting only a few minutes. At this point, the brain creates slow, high-amplitude activity known as theta waves.
  • Stage 2 (N2) sleep encompasses about 50% of a night's sleep and is marked by sleep spindles and K-complexes. This stage lasts slightly longer than the previous stage.
  • Stage 3 (N3) is deep sleep and should encompass at least 20% of a night's sleep. During this stage, the brain begins to produce the slow and deep waves of delta sleep. People are far less responsive and less aware of their external environment at this point. Delta wave sleep is often thought of as a transitional point between light and deep sleep.
  • REM sleep is characterized by rapid eye movements and increases in dreaming. REM sleep begins around 90 minutes after you fall asleep, and you may experience multiple REM cycles each night.

Delta waves are associated with the deep sleep stages: stage 3 and REM. During stage 3, less than half of brain waves consist of delta waves, while more than half of brain activity consists of delta waves during REM sleep.

How to Get More Deep Sleep

Improving your sleep hygiene can help you get more deep sleep each night. "Sleep hygiene" refers to the daily habits you follow that lead to a good night's sleep. If you're struggling, try:

  • Avoiding screens and blue light prior to bed, since the light emitted can disrupt your natural sleep patterns
  • Getting enough exercise during the day
  • Limiting your intake of caffeine and alcohol throughout the day, as both of these can disrupt your sleep
  • Making your bedroom dark, cool, and quiet and investing in a comfortable mattress and bedding
  • Setting a consistent bedtime and wake time

Sometimes, remaining in bed when you’re having trouble falling asleep can lead to feelings of frustration and stress, which can worsen your sleeplessness. If you can’t fall asleep, try getting out of bed and taking part in a relaxing activity like:

Some mental health conditions can cause problems with sleep. If you’re struggling to get enough rest due to anxiety, depression, or another issue, seeking help from a qualified mental health professional may be the right next step. A therapist or psychiatrist can help you address the underlying cause so you can get the rest you need.

Interesting Facts About Delta Waves

Interestingly, research has found that women display more delta wave activity than men. Females among most other mammalian species display a similar tendency, although researchers have not yet agreed on a specific reason why. Ketogenic diets, which are very high in fat and low in carbohydrates, can cause delta wave increases.

Brain disorders also can have an effect on the display of delta waves. Parkinson's disease, schizophrenia, and narcolepsy may be characterized by changes in delta wave activity. Even some drugs and chemicals have been shown to impact the brain's delta waves. Alcohol can also have an effect on delta waves and long-term misuse can lead to lasting changes in delta activity.

Frequently Asked Questions

How much deep sleep do you need every night?

Adults need a total of around seven to nine hours of sleep each night, and at least 20% of that time should be spent in deep sleep. The exact amount of sleep you need may vary depending on your age and other individual characteristics. Teenagers, for example, need around nine-and-a-half hours each night, while adults over age 60 often get by on much less.

What music is best for deep sleep and delta waves?

Calming, slow, instrumental music will likely be the best choice for encouraging deep sleep. One song developed specifically to induce deep sleep and delta waves is "Drifting into Delta" by Dr. Lee R. Bartel. This song has been shown to increase the time spent in slow-wave sleep.

How much deep sleep do people get on average?

Many of us don't get enough deep sleep—or enough sleep in general. Around one-third of American adults get fewer than seven hours of sleep each night. The amount of deep sleep we get each night also tends to decline with age. Adults age 60 and older may only spend about 2% of their night in deep sleep.

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Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Kendra Cherry, MSEd
Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."