The Impact of Delta Waves on Deep Sleep

woman being hooked up to sleep study machinery


A delta wave is a type of high amplitude brain wave found in humans. Delta waves have a frequency from one to four hertz 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 (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

Delta waves were first identified and described in the early 1900s after the invention of the electroencephalogram 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 three stages of sleep can begin:

  • Stage 1 (N1) is light sleep, typically beginning soon after getting into bed and lasting roughly 7–10 minutes. At this point, the brain creates a slow, high amplitude activity known as theta waves.
  • Stage 2 (N2) sleep encompasses about 50% of a night's sleep and is marked not only by sleep spindles but also K-complexes. This stage lasts slightly longer than the previous stage.
  • Stage 3 (N3) is deep sleep and should encompass about 20% to 25% 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 the external environment at this point. Delta wave sleep is often thought of as a transitional point between light and deep sleep. Previously, researchers distinguished between stage 3 and stage 4 of sleep, but they are now recognized as combined stages.

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.

It is in the next stage that REM sleep begins. This stage is characterized by rapid eye movements and increases in dreaming.

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 are all 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.

Was this page helpful?
Article Sources
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.
  1. American Psychological Association. APA Dictionary of Psychology: Delta wave. Washington, DC: American Psychological Association. 2018.

  2. Kayaba M, Park I, Iwayama K, et al. Energy metabolism differs between sleep stages and begins to increase prior to awakening. Metab Clin Exp. 2017;69:14-23. doi:10.1016/j.metabol.2016.12.016

  3. Bernardi G, Betta M, Ricciardi E, Pietrini P, Tononi G, Siclari F. Regional delta waves in human rapid eye movement sleep. J Neurosci. 2019;39(14):2686-2697. doi:10.1523/JNEUROSCI.2298-18.2019

  4. Afaghi A, O'Connor H, Chow CM. Acute effects of the very low carbohydrate diet on sleep indicesNutritional Neuroscience.11(4):146-154. doi:10.1179/147683008X301540

  5. Sekimoto M, Kato M, Watanabe T, Kajimura N, Takahashi K. Cortical regional differences of delta waves during all-night sleep in schizophrenia. Schizophr Res. 2011;126(1-3):284-290. doi:10.1016/j.schres.2010.11.003

  6. Colrain IM, Turlington S, Baker FC. Impact of alcoholism on sleep architecture and EEG power spectra in men and womenSleep. 2009;32(10):1341–1352. doi:10.1093/sleep/32.10.1341