Sleep is an activity that is essential to your overall health. From boosting daily mental functions to increasing your lifespan, sleeping plays numerous roles. Still, most people know very little about how sleeping works. There is even a common misconception that it’s a dormant, or “lazy” activity. Sleep itself is broken down into five stages. These include stages 1 through 4, with the fifth stage called the rapid eye movement (REM) stage. Disruptions in any of these stages can lead to poor quality of sleep, so it’s important to understand each one so you can take steps to gain much-needed shuteye.
Stage 1: Light Sleep
Stage 1 is referred to as “light sleep.” At this stage, you may be awakened easily without multiple attempts. Whenever you take a light nap or even meditate, you’re likely resting somewhere within stage 1. You may also daydream or start having visual hallucinations, though you’re not fully asleep yet. During stage 1, your muscles start to relax, which can cause “falling” sensations called hypnic myoclonia. According to Psych Central, stage 1 usually lasts between five and 10 minutes.
Stage 2: Deeper Relaxation
The transition from stage 1 to stage 2 of the sleep cycle is first characterized by a halt in eye movements. At this point, your eye movements stop in response to brain relaxation. Furthermore, your brain waves slow down. At the same time, however, there are short bursts of rapid brain waves called sleep spindles. According to the National Institute of Neurological Disorders and Stroke (NINDS), stage 2 comprises 50 percent of total sleeping time.
Stage 3: Beginning of Deep Sleep
The third stage of sleep is characterized by even slower brain waves called delta waves mixed in with intervals of fast brain waves. Your heart rate drops, and your body starts relaxing even more. This is the main transitional phase between light and deep sleep. During stage 3, you experience difficulties in waking up.
Stage 4: Understanding Delta Waves
Stage 4 sleep is exclusively characterized by delta waves. These brain waves inhibit any eye and muscle movement, so the body is completely still. At this point, you’re truly in “deep sleep” mode. It’s difficult to wake up during stage 4 and if you are awakened, you’ll experience extreme grogginess. People who experience snoring, sleepwalking, nightmares and incontinence likely do so at the very end of this stage. This is because you’re still in a deep sleep, but your muscles might become active. According to Psych Central, each stage 4 cycle occurs approximately 30 minutes at a time.
Some of the characteristics of stages 3 and 4 sleep are similar, but the latter is a deeper form of sleep because of the influx of delta brain waves.
Stage 5: The REM Cycle
A REM cycle occurs when your brain is more active. Also called stage 5 or paradoxical sleep, a REM cycle also makes your muscles more paralyzed. At the same time, you’ll experience increases in breathing, eye movement, heart rate and blood pressure. Such characteristics are partially responsible for dreaming. Whether you remember your dreams or not, you likely experience them during every REM cycle. According to NINDS, REM cycles make up for 20 percent of your total sleeping time. The first one occurs an average of 70 to 90 minutes after falling asleep. After you complete this fifth stage of sleep, you usually go back to stage 2.
There is much focus on getting enough REM cycles every night, but you still need to cycle through the other four stages of sleep to get there. You cannot get to stage 5 if you don’t experience the deep sleep that is characteristic of stages 3 and 4. If you don’t achieve enough REM cycles, you’re likely not getting enough quality of sleep. Caffeine, physical activity, antidepressants, alcohol and tobacco can all interrupt REM cycles and overall sleep quality. It’s important to limit items that are known to interrupt your sleep. For example, limiting caffeine during the late afternoon and evening hours can translate to better sleep quality at night.
Recommendations for Sleep
Adequate sleep is not only necessary to avoid daytime tiredness, but it’s necessary for survival and nervous system function. Over time, sleep deprivation can increase your risk for chronic diseases, such as cardiovascular disease. Adults who don’t get enough sleep are also more prone to anxiety and obesity because their bodies can’t function like they’re supposed to. NINDS says seven to eight hours of sleep is the right amount of sleep for adults. More or less sleep than this recommended about of hours may adversely affect your health over time. Children, pregnant women and teenagers require more sleep than this. Infants need the most sleep, with an average of 16 hours total in one day.
Understanding the sleep cycle is important in detecting potential problems that affect sleeping. If you fail to achieve adequate sleep despite changes in lifestyle, talk to your doctor about the possibility of an underlying medical condition that may be causing the disruption.