Your Complete Guide To Deep Sleep

When we pull the covers back on the finer points of our sleep architecture, or the organizational structure of our sleep stages and how we move through sleep cycles, one sleep stage in particular stands out for its importance to our well-being and cognitive function: deep sleep. (1)

While most people know that the REM sleep stage is when most dreaming occurs, they probably aren’t familiar with the host of biological housekeeping functions that occur during deep sleep. (2) This sleep stage does the lion’s share of the work to make us feel restored and refreshed when we wake, but it certainly doesn’t end there.

Note: The content on Sleepopolis is meant to be informative in nature, but it shouldn’t be taken as medical advice, and it shouldn’t take the place of medical advice and supervision from a trained professional. If you feel you may be suffering from any sleep disorder or medical condition, please see your healthcare provider immediately.

Long Story Short

Deep sleep, also known as slow-wave sleep, is a vital part of our sleep cycle. The time we spend in deep sleep may determine how restored and refreshed we feel upon waking.
During deep sleep, our bodies perform various biological and physiological functions, including cell and tissue repair, fortifying our immune system, and memory consolidation.
Practicing good sleep hygiene, getting enough exercise, and limiting your intake of caffeine and alcohol may be helpful ways to improve the quality and quantity of your deep sleep.

What Is Deep Sleep?

“When we’re asleep, our brain transitions through four distinct sleep stages, which range from light sleep through deep sleep and a rapid eye movement (REM) stage,” says Dr. Chelsie Rohrscheib, head sleep expert and sleep scientist at Wesper. (2) “Deep sleep occurs during the slow wave stage (stage 3, non-REM sleep) when our brain activity is at its lowest.” (2)

The deep sleep stage is also known as delta sleep because your brain’s electronic signals during this time are delta waves, which are indicators of low brain activity. (2)

During deep sleep, these may occur: (2) (3)

Muscles are fully relaxed
Blood pressure drops
Heart rate and breathing rates are at their lowest levels
Brain waves are at their slowest levels of the night
It’s difficult to awaken (even with loud noise)

How Much Deep Sleep Do I Need?

According to Rohrscheib, “The amount of deep sleep you require is highly dependent on your genetics. If we want to look at it in broad strokes, however, the average amount of deep sleep needed is 25 percent of your night — or roughly two hours for most adults.”

However, we’ll add here that sleep architecture tends to change over time. So, while you might spend a portion of your total sleep time in deep sleep, the amount of deep sleep you actually achieve is likely to change with the turn of every calendar page. The fact is, as we age, sleep quality and quantity may decrease, as does the total time spent in deep sleep or slow wave sleep time. (4)

What Happens When You Don’t Get Enough Deep Sleep?

A lack of deep sleep can look remarkably like sleep deprivation. And if you’re not getting enough, you (and your family members) will probably notice. A lack of (or insufficient) deep sleep can cause: (5)

Daytime sleepiness
Low energy
Poor focus
Impaired memory
Moodiness and irritability

Rohrscheib adds, “Chronic deep sleep loss may raise your risk for many health issues and chronic conditions, including diabetes, heart disease, hypertension, and poor mental health.” (6) (7) It’s also worth noting that emerging research shows that insufficient deep sleep can increase the risk of dementia in older adults. (8)

The Benefits of Deep Sleep

Deep sleep (N3) is the sleep stage directly responsible for our quality of sleep and how refreshed we feel upon waking. Although slow-wave sleep only accounts for about one-quarter of our total sleep time, our bodies are able to perform a whole host of biological housekeeping functions during that time.

The physiological and biological processes that occur during the N3 or deep sleep include: (2)

Cell and tissue repair
Growth hormone release
Brain maintenance
Mood regulation
Memory consolidation
Immune system strengthening (9)

Sleep Disorders Related to Deep Sleep

Aging, stress, and changes in sleep patterns due to chronic pain can reduce the amount of deep sleep we get from night to night. (2) (10)

While disorders like sleepwalking, night terrors, and bedwetting typically occur in the deep sleep stage, Rohrscheib notes that “nearly all sleep disorders can negatively affect deep sleep.” (2) She says, “Sleep disorders that commonly reduce deep sleep include insomnia, sleep apnea, and restless leg syndrome.” (11)

Tips for Getting More Deep Sleep

For anyone interested in getting more deep sleep, Rohrscheib says, “Practicing good sleep hygiene is key to improving your overall sleep quality. (12) The practices outlined below may help you get deep sleep that is consistent and uninterrupted.

Maintain a Consistent Sleep Schedule

“Maintaining a strict sleep schedule that allows you to get seven to nine hours of sleep per night will help your brain spend sufficient time in deep sleep,” says Rohrscheib. This means going to bed and waking up at the same time every day to help regulate your body’s internal clock, promoting more consistent and deep, restorative sleep. Of course that can be easier said than done — life happens, after all — so just do your best.

Create a Relaxing Bedtime Routine

Bedtime routines aren’t just for the kiddos. Calming activities before bedtime (such as reading, meditating, or taking a warm bath) can help signal to your body that it’s time to wind down and prepare for sleep. (12)

Optimize Your Sleep Space

Light and noise are not typically considered conducive to deep sleep. (13) (14) So, make sure your sleep space is cool, dark, and quiet enough to support quality sleep. You can also take a second look at your bedding, organization system, and even your room colors to design the best environment for sleep.

Skip the Stimulants

Caffeine and nicotine, close to bedtime, can interfere with sleep onset and reduce deep sleep, so you might consider skipping the evening coffee or nightcap.

Limit Screen Time

Blue light exposure can disrupt the production of sleep-inducing hormones like melatonin, so consider limiting your screen time in the evening and work toward a complete disconnect a half hour before lights out. (12) (15)

Get Regular Exercise and Mind Your Diet

“Getting sufficient daily exercise and eating a healthy diet are two important tickets to boosting your deep sleep,” says Rohrscheib. While regular exercise can help alleviate stress and anxiety, it can also promote deeper, more restorative sleep. Just be sure to avoid vigorous exercise close to bedtime. (16)

Address Health Issues

Bearing in mind that sleep disorders, chronic pain, and stress can put a hitch in your deep sleep giddyup. Rohrscheib suggests speaking with your doctor to address any underlying issues that may impact your chances of getting adequate deep sleep.

The Last Word From Sleepopolis

Deep sleep is the most restorative part of our sleep cycle, and it plays a significant role in physical and mental well-being. Improving the quality and duration of your deep sleep through improved sleep hygiene might be the ticket to better health and mornings.

Sources

Yetton, B. D., McDevitt, E. A., Cellini, N., Shelton, C., & Mednick, S. C. (2018). Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks. PLOS ONE, 13(4), e0194604. https://doi.org/10.1371/journal.pone.0194604
Patel AK, Reddy V, Shumway KR, et al. Physiology, Sleep Stages. [Updated 2024 Jan 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526132/
U.S. Department of Health and Human Services. (n.d.). What happens during sleep? Eunice Kennedy Shriver National Institute of Child Health and Human Development. https://www.nichd.nih.gov/health/topics/sleep/conditioninfo/what-happens
A Good Night’s Sleep. National Institute on Aging. https://www.nia.nih.gov/health/sleep/good-nights-sleep
Chattu VK, Manzar MD, Kumary S, Burman D, Spence DW, Pandi-Perumal SR. The Global Problem of Insufficient Sleep and Its Serious Public Health Implications. Healthcare (Basel). 2018;7(1):1. Published 2018 Dec 20. doi:10.3390/healthcare7010001
Pan, Y., Zhou, Y., Shi, X., He, S., & Lai, W. (2023). The association between sleep deprivation and the risk of cardiovascular diseases: A systematic meta‑analysis. Biomedical Reports, 19, 78. https://doi.org/10.3892/br.2023.1660
Centers for Disease Control and Prevention. (2021, June 17). Effect of inadequate sleep on frequent mental distress. Centers for Disease Control and Prevention. https://www.cdc.gov/pcd/issues/2021/20_0573.htm
Himali JJ, Baril A, Cavuoto MG, et al. Association Between Slow-Wave Sleep Loss and Incident Dementia. JAMA Neurol. 2023;80(12):1326–1333. doi:10.1001/jamaneurol.2023.3889
Yang, H., Engeland, C. G., King, T. S., & Sawyer, A. M. (2020). The relationship between diurnal variation of cytokines and symptom expression in mild obstructive sleep apnea. Journal of Clinical Sleep Medicine, 16(5), 715–723. https://doi.org/10.5664/jcsm.8332
Jonas Beck, Erna Loretz, Björn Rasch, Stress dynamically reduces sleep depth: temporal proximity to the stressor is crucial, Cerebral Cortex, Volume 33, Issue 1, 1 January 2023, Pages 96–113, https://doi.org/10.1093/cercor/bhac055
Shahveisi K, Jalali A, Moloudi MR, Moradi S, Maroufi A, Khazaie H. Sleep Architecture in Patients With Primary Snoring and Obstructive Sleep Apnea. Basic Clin Neurosci. 2018;9(2):147-156. doi:10.29252/NIRP.BCN.9.2.147
Foster RG. Sleep, circadian rhythms and health. Interface Focus. 2020;10(3):20190098. doi:10.1098/rsfs.2019.0098
Tan DX, Reiter RJ, Zimmerman S, Hardeland R. Melatonin: Both a Messenger of Darkness and a Participant in the Cellular Actions of Non-Visible Solar Radiation of Near Infrared Light. Biology (Basel). 2023;12(1):89. Published 2023 Jan 6. doi:10.3390/biology12010089
Yuki Yamagami, Kenji Obayashi, Yoshiaki Tai, Keigo Saeki, Association between indoor noise level at night and objective/subjective sleep quality in the older population: a cross-sectional study of the HEIJO-KYO cohort, Sleep, Volume 46, Issue 5, May 2023, zsac197, https://doi.org/10.1093/sleep/zsac197
Silvani MI, Werder R, Perret C. The influence of blue light on sleep, performance and wellbeing in young adults: A systematic review. Front Physiol. 2022;13:943108. Published 2022 Aug 16. doi:10.3389/fphys.2022.943108
Alnawwar MA, Alraddadi MI, Algethmi RA, Salem GA, Salem MA, Alharbi AA. The Effect of Physical Activity on Sleep Quality and Sleep Disorder: A Systematic Review. Cureus. 2023;15(8):e43595. Published 2023 Aug 16. doi:10.7759/cureus.43595

Rohrscheib, Chelsie. Author Interview. April 8, 2024.