Within the last 100 years, sleep scientists have begun to chart the various stages of sleep.
In particular, two main sleep stages have been discovered, namely REM sleep and non-REM sleep.
Furthermore, within the non-REM stage, 3 stages have been proposed to distinguish the unique characteristics of each state, specifically stage 1, stage 2 and stage 3.
Slow-Wave Sleep and Your Health
In this article, we will focus on stage 3 of non-REM sleep, discussing 6 facts that distinguish this sleeping state from other others.
Predominance of Delta Waves
Stage 3 of non-REM sleep, often called slow-wave sleep (SWS sleep) or even deep sleep, is characterized by high-amplitude, low frequency brain waves when the electrical activity of the brain is measured using an electroencephalogram (EEG).
In particular, these delta sleep waves must be present for at least 20% of a period of time (30 seconds) for the period to be considered slow-wave sleep.
Although recent research has discovered even lower frequency brain waves, delta waves have traditionally been considered the lowest frequency brain waves with a frequency of 1-4 hertz. This is an indication of the depth of the corresponding sleep in this stage as well as how relaxed the brain is.
Most notably, brain activity and muscle activity decrease considerably when delta waves are shown on an EEG test.
Slow-Wave Sleep Varies with Age
What’s fascinating about slow-wave sleep is that it varies depending on how old you are. In particular, children and young adults experience this sleep state much more frequently than older adults.
Even further, the elderly hardly experiences this state at all, with about 2-5% of their overall sleep being characterized by pronounced delta waves.
Babies, on the other hand, are thought to experience as much as half of their overall sleep in slow-wave sleep, with the other half being REM sleep.
Slow-Wave Sleep Varies Throughout the Night
Slow-wave sleep is also more pronounced in the beginning of the night and decreases in quantity as the night progresses. Towards the end of the night, our sleep cycle is dominated by REM sleep and light sleep.
Slow-Wave Sleep Aids Memory Consolidation
Slow-wave sleep is thought to play an important role in the consolidation of long-term memories, particularly declarative memories.
Declarative memory refers to memories that can be consciously remembered, typically facts and events.
What’s interesting is that that procedural memory formation is not as enhanced as declarative memory formation during slow-wave sleep. Procedural memories are memories that are concerned with skills and actions, like combing your hair.
These kinds of memories are typically called implicit because they build upon previous memories. REM sleep is thought to enhance any kind of procedural task that we learn during the day.
Deprivation Leads to Disorientation
One of the most prominent characteristics of slow-wave sleep is that sleepers will appear disoriented and even irritable if awakened during this stage. This is a sign of how crucial this stage is for restoration and integration, as any interruption is not welcomed by the sleeper.
If you frequently wake up in the morning to an alarm clock, then you’ve probably experienced some of these negative effects, as your sleep cycle was likely cut short by the arbitrariness of the clock.
This is why it is critical to rely on your natural circadian clock to determine the perfect time to sleep and rise.
Deprivation Leads to Compensation
Slow-wave sleep is so important for sleep health that any disruption will lead to the body compensating later in the night.
If you only enter a light sleep throughout the night, perhaps because you are awakened by some environmental stimulus, then your body will enter slow-wave sleep more quickly and more frequently to balance out the sleep cycle.
This is fascinating because it shows that the entire sleep cycle is interconnected and that an imbalance in any one part can result in an imbalance in another part.
Thus, quality of sleep is just as important as quantity of sleep. Sure, it’s important to get your nightly 8 hours, but just as critical is to cycle through all stages of the sleep cycle.
Yet, if you happen to be deprived of one part of the sleep cycle, the compensatory states will actually be less effective and restorative, as the body is trying to cram them in in an unnatural way.
All the more reason to turn off the television and limit blue light exposure before bed.
Our Final Thoughts on Slow-Wave Sleep
The underlying brain waves that characterize slow-wave sleep are fascinating due to how close they flirt with death. If our brain waves were of a lower frequency than delta waves, then we would be considered brain dead.
Yet, there is still much to learn about slow-wave sleep. As our technology advances, our knowledge of slow-wave sleep will surely improve.
Feature image via Wealth In Health TODAY