Sleep is powerfully rejuvenating and a vital ingredient for good health!
There are two kinds of sleep – rapid eye movement (REM) sleep and nonREM (NREM) or slow wave sleep. REM sleep is characterized by rapid eye movements that occur during this stage of sleep. NREM sleep is divided into four stages. As a person begins to fall asleep, one enters stage one and two of slow wave light sleep, followed by 70 to 100 minutes in stages 3 and 4 of deep sleep. During deep sleep muscles relax, heart rate and blood pressure decreases, and no eye movements occur. Sleep then lightens and a REM period follows. This cycle is repeated at about 90 minute intervals throughout the night. The cycles are similar, though there is less stage 3 and 4 sleep and more REM sleep toward the morning. Four to six REM periods occur per night.
Rem sleep makes up 50% of sleep in babies, but falls rapidly as one gets older to plateau at about 25% for most of one’s life. In the elderly REM sleep falls to about 20%. Children have more total sleep time and stage 4 sleep than adults.
During the initial light sleep, the vast amount of information received that day is erased, and only the memories of importance are kept. If light sleep is disrupted, then one battles to remember what happened the previous day and one becomes disorientated. Then one goes into deep sleep during which growth hormone is released, and lots of bodily repair and housekeeping is performed. If deep sleep is disrupted, people become very unhealthy very quickly. As one then drifts into REM sleep, one starts to dream, and once the dream has finished, about 90 minutes has elapsed. This sleep cycle is then repeated several times throughout the night.
During REM sleep, the EEG resembles that of a person who is awake. Humans woken when they are in REM sleep, as illustrated on their EEG brain scans, report that they were dreaming; however, others awakened from slow wave sleep, report no dreaming. Most dreams occur during REM sleep.
In experimental animals sleep is necessary for learning and memory consolidation. Learning does not improve performance until a period of slow wave or slow wave plus REM sleep has occurred.
When you are dreaming, you are very close to the waking state and thus this is a healthy, safe time to wake up. One does not want to wake up in deep sleep as this will affect the day ahead. The best way to ensure that one wakes up after REM sleep is to work out using 90 minute slots, what time you should asleep by, bearing in mind when you plan to wake up. If one sleeps for 450 minutes (7.5 hours), then awaking will occur after the fifth REM period.
Professor Richard Wiseman, explores the science of sleep and dreaming in his new book “Night School : Wake up to the power of sleep”. One of his findings is that dreams early in the night, which you most likely will not remember, are very negative, while the dreams just before you wake up are much more positive. He suggests that the reason for this is because while sleeping one is working through the anxieties of the day and looking for solutions, so that when we wake up, we are ready to face the day. Professor Wiseman also suggests that depressed people dream about five times as much as non-depressed people, and because they spend more time in REM sleep and less time in deep sleep, with less repair of the body, they wake up feeling shattered and exhausted.
To avoid jet lag, he further advises that one tries to match your circadian rhythm with that of your destination – when climbing onto the plane, set your watch to your destination time. In this way you will psychologically start adapting to your new time immediately. To avoid jet lag, it is worth remembering: “Fly east, fly early; fly west, fly late”
We spend a third of our lives asleep. The better we understand the physiology of sleep, the more we can use this wonderful therapy to improve our daily health and vitality.
HEALTH INSIGHT
MARCH 2017