Lack of Deep Sleep: Evaluating Causes to Improve Sleep Quality

Almost everyone could benefit from getting more sleep, and deep sleep seems even more desirable. Indeed, a lack of deep sleep can have serious health consequences. What exactly constitutes “deep” sleep, and how do you determine if you’re getting enough of it? And what can be done if you’re not? 

Deep sleep refers to slow-wave sleep, the deepest stage of sleep and the most difficult from which to wake someone. Characterized by slow electrical activity largely in the frontal lobes of the brain, it occurs more in the first third of the night. It is sometimes called stage 3 or N3 sleep, and includes what was previously known as stage 4 sleep. 

Children have the highest amounts of slow-wave sleep. Over the course of their lifetimes, women experience more deep sleep than men. In a study published in the Archives of Internal Medicine, research showed men’s slow-wave sleep gradually decreased with age while women’s percentages slightly increased. Between ages 37 and 54, men had an average of 11.2% slow-wave sleep and women had 14.2%. Beyond age 70 the gap widened to 5.5% in men and 17.2% in women.

Health Benefits of Deep Sleep

During deep sleep, the body releases growth hormones important for the development and repair of tissues. It is of vital importance for normal growth during childhood, and has an ongoing role in adults, building muscle mass with exercise and alleviating the effects of normal wear and tear on the body. The increased blood flow to the muscles during deep sleep aids in these processes.

 Deep sleep may also have important roles in clearing metabolic waste from the brain through the glymphatic system (including a protein called beta-amyloid). This improves memory processing and consolidation, optimizes immune system function, and restores cell energy stores.

How to Determine If You Are Getting Enough Deep Sleep

The depth of sleep may correspond to its perceived quality—you can usually tell when you aren’t getting enough deep sleep. Light sleep may be fragmented, punctuated by frequent arousals (transitions from deep to light sleep) or awakenings. When you wake up, you may feel unrested, and experience sleepiness and fatigue throughout the day.

Unfortunately, presently there is no accurate and easy way to measure your sleep stages and determine whether you are getting enough deep sleep on a nightly basis. The gold standard test for sleep diagnosis is the polysomnogram, a formal study done at a sleep center that measures: 

  • Electrical activity of the brain (and, by extension, sleep stages) with an EEG
  • Muscle activity in the chin
  • Eye movements
  • Breathing patterns
  • Oxygen levels
  • The heart rhythm with an electrocardiogram (ECG or EKG)
  • Leg movements

This testing has obvious limitations as it is somewhat disruptive to sleep, incompatible with long-term sleep monitoring, relatively expensive, and inaccessible. Though it is highly accurate at determining the presence and amount of deep sleep, it is not useful in the slightest to someone who introspectively wishes to assess their sleep.

Wearable technology, including numerous fitness trackers and associated devices, seems to offer the promise of convenience and long-term assessment. These devices are highly dependent on the detection of movement, heart rate, and sometimes other variables like oxygen levels or even EEG. These are imperfect surrogates for the hallmarks of deep sleep. Improvements in the science behind this health technology may someday improve the accuracy of the measurements. This will give us a new way to understand the depth of the sleep experienced each night.

Causes for Lack of Deep Sleep

Consider these potential contributors to a lack of deep sleep:

Weakened sleep drive: Sleep drive can be weakened, and the proportion of deep sleep reduced, by taking naps or spending a prolonged period in bed to the point that there’s no longer the innate ability to sleep.

Sleep disorders: There are certain sleep disorders that may disturb deep sleep. Sleep apnea and periodic limb movements of sleep cause recurrent awakenings. These disruptions may reduce deep sleep. Effective treatment may cause a rebound of deep sleep and further normalization of the balance of sleep stages over time.

Substance use and withdrawal: Caffeine is a stimulant that reduces deep sleep. It may have effects even hours after its consumption. Similarly, the use of benzodiazepine and opioid medications reduces deep sleep. (Conversely, withdrawal from a benzodiazepine medication seems to increase deep sleep.) Trazodone, an older antidepressant that is often used as a sleep aid, seems to increase deep sleep through effects on the histamine system. Both marijuana and lithium, a medication for bipolar disorder, may also enhance slow-wave sleep. Interestingly, the non-benzodiazepine sleep aids (zolpidem, eszopiclone, and zaleplon) seem to have no effect on deep sleep.

Solutions

Though it is recognized that deep sleep is important to the perceived quality of rest and significantly impacts health and quality of life, it is surprising that we have relatively little information on how to enhance the amount of deep sleep we get. Still, there are possible solutions:

Boost sleep drive: Extended periods of wakefulness enhance what’s known as the homeostatic sleep drive, increasing deep sleep. In other words, you may need to reduce the opportunity for sleep so that when you do get to bed, you achieve deep sleep. Sleep consolidation, or sleep restriction, is an effective treatment for insomnia that is integrated into a cognitive behavioral therapy for insomnia (CBTI) program. Sleep deprivation may enhance sleep depth when sufficient sleep occurs.

Follow a circadian rhythm: Deep sleep follows a circadian pattern with greater amounts in the early part of the night. It may be enhanced by keeping to a regular sleep-wake schedule, including on weekends, and using morning sunlight as a consistent cue to the circadian system immediately upon awakening. When sleep is irregular, the disturbed timing of deep sleep may reduce it.

Behaviors and environment: Further research is needed to understand the effects of behaviors and the environment on the initiation and maintenance of deep sleep. Exercise and adequate daytime physical activity may help, but the ideal timing is less certain. Taking a warm bath or shower about 90 minutes before your anticipated bedtime may help with the circadian onset of sleep. There is some evidence that a cool bedroom temperature enhances deep sleep. Excessive environment noise or light, or an elevated temperature, may undermine it. It is also possible that external devices—including those that emit varying electrical patterns, vibrations, sounds, or light—may have a role in enhancing sleep depth. Whether a headband that purports to change sleep depth by altering brain waves actually works remains to be seen.

Risks Associated With Lack of Deep Sleep

There is clear evidence that a lack of sleep has profound effects on health. When deep sleep is compromised, the quality of sleep plummets. As noted above, there can be important impacts on the body and, importantly, the brain. Consider these consequences:

Pain: Chronic pain is exacerbated by reduced deep sleep. This may manifest in various ways, including as a clinical diagnosis of fibromyalgia. As sleep depth improves, pain may abate.

Impaired growth: Children who have untreated sleep disorders like sleep apnea experience reduced deep sleep. This impairs the release of growth hormone. Fortunately, once effectively treated, these children may experience a growth rebound.

Dementia: The accumulation of beta-amyloid plaques within brain tissue characterizes the development of memory impairment and Alzheimer’s disease. A lack of deep sleep, and the disturbance of the process of cleansing the brain of these proteins, may accelerate this degeneration.

It is likely that a lack of deep sleep also contributes to immune system dysfunction and the risk of routine infections, such as the common cold or influenza, as well as the risk for chronic diseases like cardiovascular disease and even cancer.

A Word From Verywell

If you are concerned about a loss of deep sleep, consider what’s in your control. Try to optimize the consistency of your sleep-wake schedule, including weekends. Create an ideal sleep sanctuary, preserving the bedroom as a space for sleep and eliminating disruptive electronics. Avoid naps and ensure you are not spending too much time attempting to sleep (most adults need 7 to 9 hours of sleep to feel rested, but older adults may only need 7 to 8 hours). Reduce caffeine consumption and avoid other substances that may reduce deep sleep. Finally, if you suspect you may have a sleep disorder like sleep apnea or insomnia, get evaluated by a board-certified sleep medicine physician. These simple changes may be the key to ending a lack of deep sleep, promoting both well-being and long-term health benefits.

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Article Sources

  1. Mander BA, Winer JR, Walker MP. Sleep and human aging. Neuron. 2017 Apr 5;94(1):19-36. doi:10.1016/j.neuron.2017.02.004.


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