Sleep is essential for our bodies to heal and our minds to rest. The most important phase of sleep is phase 3, non-REM sleep or delta (slow wave) sleep, which occupies 25% of our total sleep cycle and is known as the “deepest” sleep period. It is in this stage when sleep is most restful, since it helps our bodies to recover and grow, boosts the immune system and other key body processes, and contributes to insightful thinking, creativity and memory. Only the last two stages of sleep, deep sleep and rapid eye movement (REM) sleep, are considered restorative.
During N1 sleep, the body has not completely relaxed, although body and brain activities begin to decrease with periods of brief movements (spasms). Problems with getting a good night's sleep on a regular basis may be a symptom of sleep disorders or other health conditions. During REM sleep, the eyes move quickly in a variety of directions, but they don't send any visual information to the brain. In an initial experiment, Johnson and his collaborators compared 3 nights of phase 4 deprivation in 7 young adults and 3 nights of REM deprivation in 7 young adults.
REM sleep is known for the most vivid dreams, which is explained by the significant increase in brain activity. As the night progresses, a person who sleeps uninterruptedly may not spend much more time in phase 1 as they progress through other sleep cycles. Sleepwalking can be dangerous, because sleepwalkers can accidentally get hurt by falling or touching a sharp object. In general, these studies indicate that the propensity for daytime sleep increases by causing an increase in pressure in the slow wave sleep (SWS) by interrupting nighttime slow wave activity (SWA), while the propensity for nighttime sleep and SWA are reduced after a nighttime nap, during which much of the pressure of the SWA dissipates.
The role of the circadian pacemaker in regulating non-REM and REM sleep was further investigated using a forced desynchrony protocol in which subjects programmed sleep-wake cycles well outside the circadian range. It remains to be established whether these individual differences in SWS and its genetic predictors are associated with sleep and circadian disorders. It should be noted that these age-related changes in SWS and sleep continuity are observed even in healthy people without sleep problems and without sleep disorders. Getting enough restorative deep and REM sleep is essential for our physical and mental health. To ensure you get enough restorative deep and REM sleep each night, it's important to practice good sleeping habits such as going to bed at the same time each night, avoiding caffeine late in the day, avoiding screens before bedtime, exercising regularly, and avoiding alcohol before bedtime.
Additionally, if you're having trouble sleeping or suspect you may have a sleeping disorder, it's important to speak with your doctor.