Last week, we looked at some general information about how challenging it can be to ensure we are sleeping soundly and adequately. Still, a question remains as to why we do sleep. While some disparity amongst sleep experts persists, there are some fundamental reasons for our restful sleep to enhance our lives.
Many people exacerbate their sleep problems because they do not have a good understanding of the sleep process. Sleep, like oxygen, food, and water, is one of our basic daily needs. Like hunger and thirst, it is a drive… our body will eventually, when faced with no other options, force us to sleep. Sleep loss increases the sleep drive and promotes good sleep – much like when we are very hungry, we find ourselves more likely to eat or even eating more voraciously.
You might have noticed that you occasionally had a relatively good night’s sleep after one or several nights of poor sleep. Such a pattern demonstrates the sleep drive in action. A natural accumulation of sleep need that occurs as we go through the day plays a part in the regulation of normal sleep.
In other words, under normal conditions, sleep debt (sleep loss) “fuels” (drives) good sleep at night. Indeed, the drive to sleep gets stronger the longer one is awake before attempting to sleep. For example, a person is much more likely to sleep for a long time after being awake for 16 hours in a row then after being awake for only 2 hours. Most persons who have sleep problems are focused on the negative consequences of insufficient sleep and forget that some sleep debt promotes a “healthy appetite” for sleep. Our attempts to recover lost sleep by trying to sleep more the next night or taking long naps during the day weaken the sleep drive and prolong our sleep difficulties. We’ll elaborate on this in just a few minutes.
Although science still has much to learn about the biological purpose of sleep, we already know a great deal about the human sleep process. Many research studies have shown that sleep is an active process made up two distinct states (Rapid Eye Movement or REM sleep and non-REM sleep). Non-Rapid Eye Movement or Non-REM sleep occupies about 75 to 80% of the night’s sleep of a “typical” young, healthy adult. The rest of the night’s sleep is REM sleep. Non-REM sleep consists of several stages, marked by their special brain-body activity patterns. Non-REM sleep is divided into three stages going from lightest (Stage N1) to deepest stages (Stage N3).
During a typical night of sleep, the Non-REM and REM stages of sleep occur in consistent and predictable cycles. When good sleepers go to sleep at night they usually experience a period of relaxed wakefulness. The length of this period of relaxed wakefulness varies from one person to the next but it is typically less than 30 minutes.
About 70 to 90 minutes into the night the first REM sleep occurs. Usually, this first REM period is relatively short and is followed by a return to a lighter stage of sleep. The time from sleep onset to the end of the first REM period constitutes the first sleep cycle. For the rest of the night, REM sleep alternates with Non-REM sleep (primarily stage N2) in roughly 90-minute cycles.
Most deep sleep occurs early in the sleep period. Because most people sleep at least 3 hours, they are rarely deprived of this deep sleep stage. Some wakefulness is a normal part of the night’s sleep even in good sleepers and A few brief awakenings do not need to be a cause for concern. These awakenings become more frequent closer to an individual’s morning waketime. This explains why most people are more easily awakened in the later part of the nocturnal sleep period. This also means that even when you sleep poorly, you are unlikely to be totally deprived of the deepest, most restorative stage of sleep.
REM (dreaming) periods become longer toward the morning rising time. This is why we are more likely to awake from a dream during the second half of the night. As the night progresses our dreams may become more complex and/or vivid, explaining why nightmares are more common during the last third of the sleep period.
There are two basic processes that regulate sleep and wakefulness. One is the normal accumulation of sleep debt as the day goes on, which we mentioned a few minutes ago (in other words, the more time that passes after we wake up for the day the greater the sleep debt). This is what we refer to as the “sleep drive”. The other process is determined by our biological clock. It is called the “circadian process.”
Next week, I will delve a bit deeper into these two processes that regulate our sleep so that we can be sure we are getting the type of restorative and enervating sleep that we need! If you’re looking for some tips on getting better sleep in the meantime, I shared some tips with Reader’s Digest recently that you can get started with.
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