What Are Slow Wave Delta Sleep Stages?
Deep sleep (also known as slow wave sleep or Delta sleep) is recognized by EEG activity with high voltage (75 µV) waves with a frequency range typically between .5 Hz and 3.5 Hz. Longer periods of Deep sleep occur in the first part of the night, and Delta sleep waves are present primarily in the first two sleep cycles. In addition, children and young adults will have more total Deep sleep per night than older adults. Young adults typically spend 20% to 25% of their sleep in this stage, while the elderly’s Deep sleep drops to about 3% by age 75. However, a number of medical studies, demonstrate that this is not an uncommon finding by mid-life.
After we exercise our muscles need to rest. It appears that the brain is no different and that the rest it requires, occurs during Deep sleep. During this stage of sleep, there is a significant decrease in cerebral functioning and metabolic rate and a drop in cerebral blood flow. The activity falls to about 75 percent of the level found in wakefulness. The regions of the brain that are most active when awake have the highest level of deep or slow waves during slow-wave sleep, as they need the greatest rest. All of these factors indicate a more restful state is being induced in the brain regions that need them most and that this rest occurs during Deep sleep.
Sleep deprivation studies also demonstrate that the primary function of Deep sleep is to allow the body and brain to recover from daytime activities. When sleep-deprived humans return to normal sleep, the recovery percentage for each stage of sleep is not the same. Only 14% of light sleep is regained after sleep deprivation, but 68% of Deep sleep and 53% of REM sleep are regained. This suggests that Deep sleep is more important than the other stages of sleep, as it returns immediately in greater quantity.
It’s also noteworthy that food proteins ingested during the day are synthesized into complex proteins of living tissue to allow for the healing of muscles as well as all bodily tissues during delta sleep. In addition, glial cells, the major cell type of the nervous system are also restored during this stage to provide energy for the brain. These activities are facilitated by growth hormone, which, is secreted during Deep sleep – not a coincidence.
Another key function of Deep sleep is memory consolidation. Impaired memory consolidation has been seen in individuals with primary insomnia who have less Deep sleep and do not perform as well as those who are healthy in memory tasks following a period of sleep.
Deep sleep is very much associated with a decrease in sympathetic and an increase in parasympathetic activity of the Autonomic Nervous System (ANS), demonstrating a shift in balance of the ANS from flight or fight to rest and rejuvenation. This is why Deep sleep is stress relieving, creates a sleep environment with fewer awakenings and arousals to promote greater sleep maintenance and causes a reduction in anxiety and depression.
In essence, Deep sleep relaxes and heals the body and mind and undeniably, is the most important sleep stage for physical restoration and rejuvenation and plays a significant role in emotional and mental processes. This is why, one of the greatest functions of the SOLTEC•HEALTH™ System is to support an environment that produces more normal amounts of Delta wave sleep.