5 Stages of Sleep
1) Stage 1: is the beginning of the sleeping cycle, a relatively light sleep stage. Stage 1 is often considered the transition period between wakefulness and falling asleep. In Stage 1, the brain produces high amplitude theta waves, which are slow brain waves. This is a relatively brief period that generally lasts only 5 to 10 minutes.
2) Stage 2: is the second of the sleep stages and lasts generally about 20 minutes. The brain begins producing sleep spindles, bursts of rapid, rhythmic brain wave activity. Your heart rate begins to slow and body temperature starts to decrease.
3) Stage 3: is when deep, slow brain waves, known as delta waves, start to emerge. Stage 3 is a transitional period between light and very deep sleep.
4) Stage 4: Sometimes referred to as Delta Sleep because of the slow ‘delta’ waves occurring in the brain at this time. Stage 4 is a very deep sleep lasting approximately 30 minutes. Delta Sleep is the deepest of the sleep stages and the most difficult in which to wake a sleeper. Sleep walking, Talking in your sleep, and bed wetting are most likely to occur near the end of Stage 4.
5) Stage 5: Known as REM (Rapid Eye Movement) sleep, Stage 5 is when most dreaming occurs. REM sleeping is characterized by eye movement, increased respiration rate, and increased brain activity. REM sleep is also referred to as ‘paradoxical sleep’ because while the brain and other body systems become more active, muscles become more relaxed. Dreaming is a result of the increased brain activity, voluntary muscles become paralyzed. On average, we enter the first REM Sleep stage about 90 minutes after falling asleep. The first REM cycle may last only a short time, but each cycle becomes longer and can last up to an hour as sleep progresses.
Sleep does begin in Stage 1 and progresses into and through stages 2, 3, and 4. After reaching Stage 4, Stage 3 and then Stage 2 are repeated before entering Stage 5 (REM). Upon completion of Stage 5 REM sleep, the body usually returns to Stage 2. A person will cycle through these sleep stages approximately 4 or 5 times throughout the night.
So, how much sleep is “enough” sleep? In March 2015, eighteen leading scientists and researchers formed an expert panel for the National Sleep Foundation. For adults, the panelists official recommendations were that people ages 18-64 need 7-9 hours of quality sleep per night and those 65+ need 7-8 hours.
A 2006 survey conducted by The Harvard Women’s Health Watch found that more people than ever before were sleeping less than six hours a night and 75% of us had sleep difficulties at least a few nights per week. More important is chronic sleep loss, which can contribute to health problems such as weight gain, high blood pressure and a decrease in the immune system’s power. Sleep problems seem to be on the increase as our society is changing.
The Harvard Women’s Health Watch suggested six reasons to get enough sleep:
- Improve Learning and Memory: Sleep helps the brain commit new information to memory through a process called memory consolidation. In studies, people who slept after learning a task, tested better on that task than those who didn’t sleep. Whether we’re learning math, how to play the piano, how to perfect our golf swing, or how to drive a car, sleep helps enhance our learning and problem-solving skills. Sleep also helps us pay attention, make decisions and be creative.
- Control Metabolism and Weight: Chronic sleep deprivation may cause weight gain by affecting the way our bodies process and store carbohydrates. Sleep also helps maintain a healthy balance of the hormones that make us feel hungry (ghrelin) or full (leptin). When we don’t get enough sleep, our level of ghrelin goes up and our level of leptin goes down. This makes us feel hungrier than when we’re well-rested.
- Maintain Safety: Not getting enough sleep contributes to a greater tendency to fall asleep or fight the urge to fall asleep during the daytime. These lapses may cause falls and mistakes such as medical errors, air traffic mishaps, and road accidents.
- Improve Mood: Sleep loss may result in irritability, impatience, inability to concentrate, and moodiness. Too little sleep can also leave us too tired to do the things we like to do.
- Maintain Cardiovascular Health: Serious sleep disorders have been linked to hypertension, increased stress hormone levels, irregular heartbeat, and stroke.
- Avoid Disease: Sleep deprivation alters immune function, including the use of the body’s killer cells to fight common infections. Giving your body the required amount of sleep may also help fight cancer, kidney disease, and diabetes.
As you can see, sleep plays a vital role in good health and well-being throughout our lives. Getting enough quality sleep at the right time can help protect our mental health, physical health, quality of life, and safety. The way we feel while we’re awake depends in part on what happens while we’re sleeping. During sleep, our body is working to support healthy brain function and maintain our physical health.
Sleep supports healthy growth and development. Deep sleep triggers the body to release the hormone that promotes normal growth in children and teens. This hormone also boosts muscle mass and helps repair cells and tissues in children, teens, and adults. Sleep also plays a role in puberty and fertility.
The damage from sleep deficiency can occur in an instant, such as a car crash, or it can harm us over time, such as when ongoing sleep deficiency causes some chronic health problems. It also can affect how well we think, react, work, learn, and get along with others.
Studies also show that sleep deficiency alters activity in some parts of the brain. If we’re sleep deficient, we may have trouble making decisions, solving problems, controlling our emotions and behavior, and coping with change. Sleep deficiency also has been linked to depression, suicide, and risk-taking behavior.
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