SleepPosted 8 years ago under Uncategorized
We spend, on average, a third of our lives asleep. When we’re sleeping, it doesn’t look like much is going on. We barely move and we rarely speak. But our bodies are very much at work, balancing hormones; raising levels of some hormones, lowering levels of other hormones. Also our bodies are repairing our tissues and recharging our minds to prepare us for the next day.
What Happens When We Sleep
The experts have previously broken down sleep into five stages. Recently this has been changed to combine stages 3 and 4 into one stage. The first three stages are called stage 1, stage 2, and stage 3. The other commonly used term for stages 1-3 is NREM or non rapid eye movement sleep. The last stage is REM or rapid eye movement sleep. (1)
State 1 is in-between consciousness and sleeping. In this stage of sleep, we are still somewhat aware of our surroundings, as this is the lightest stage of sleep. At this stage, many of us don’t realize that we are asleep yet, and it is very common for someone when woken up from this stage of sleep to report that they were not yet asleep.
In this stage of sleep, brainwaves change from fast pulsing beta waves to slower alpha waves; and then after some time even slower theta brainwaves.
It is not unusual at this stage of sleep to experience something known as hypnagogic hallucinations. These are extremely vivid sensations experienced as one is falling asleep. A sensation of weightlessness, the feeling of falling, the sensation of being touched, or hearing someone call your name are typical examples of hypnagogic hallucinations.
Another phenomena experienced by many in this stage of sleep is the myoclonic jerk. This is when one is falling asleep and then abruptly startled awake, but seemingly without any cause. This is a type of myoclonus reflex. Although very disconcerting, myoclonic jerks are common during stage 1 sleep. (2)
This is a deeper onset of unconsciousness. At this stage of sleep we are unaware of our surroundings. Breathing and heartbeat are regular, and the body’s temperature drops slightly. This temperature drop is only by a couple of degrees Fahrenheit, but it is crucial in order get to deeper stages of sleep. This is why sleeping in a cool room tends to be helpful; most prefer temperatures between 65 and 75 degrees Fahrenheit. (3)
Dreams are more likely to occur in stage 3 than in the previous stages of NREM sleep. A small drop in blood pressure occurs. Breathing slows. Brain activity slows. Delta brainwaves are common in this stage. Many different hormones are released. Blood supply to muscles increases, tissues are repaired, and growth occurs. This stage also restores energy to the body. (4)
Stage 4 or REM Sleep
REM sleep stands for rapid eye movement. The cardiovascular system speeds up, heart rate increases, blood pressure rises, and our breathing becomes more rapid. Brainwave activity increases. In this stage of sleep, alpha waves are common.
It was believed that dreams only took place during REM sleep. Actually, dreaming is more common in REM sleep than in the other stages of sleep, but dreams can occur at every stage of sleep.
During REM sleep, dreams tend to be intense. This is why our bodies paralyze us until we cycle out of REM sleep. This paralysis is caused by chemical signals sent from the brain that inhibit us from acting out our dreams.
REM sleep plays a crucial role in our mental health, and REM sleep is the stage of sleep needed for memory consolidation. (5)
After stage 4, or REM sleep, the stages are repeated, excluding stage 1. So on a typical night, the sleeping stages would occur as 1,2,3, and 4, then stages 2,3,4, and 2,3,4 again and again until awake. The length of each stage depends on many factors, including our quality of sleep. REM sleep usually lasts 90 min. (6)
How Much Sleep Do We Need?
Sleep needs vary by age. The following are recently revised guidelines from The National Sleep Foundation’s panel on how many hours of sleep we need at different ages.
- Newborns (0-3 months): 14-17 hours a day.
- Infants (4-11 months): 12-15 hours a day.
- Toddlers (1-2 years): 11-14 hours a day.
- Young children (3-5 years): 10-13 hours a day.
- Children (6-13): 9-11 hours a day.
- Teenagers (14-17): 8-10 hours a day.
- Young adults (18-25): 7-9 hours a day.
- Adults (26-64): 7-9 hours a day.
- Older adults (65+): 7-8 hours a day.
How well one sleeps is one of the best predictors for longevity. Sleep slows the aging process. Those who sleep poorly actually age faster. Chronic sleep deprivation can shorten a lifespan by an average of eight to ten years. Good sleep habits are a necessary component to a healthy lifestyle.