Our next blog series comes from a different kind of book that challenges us in a different kind of way. Why We Sleep: Unlocking the Power of Sleep and Dreams by Matthew Walker, PhD, helps us to understand the science behind sleep and recovery and encourages us to take our sleep just as serious as we take our waking hours. Taking on the challenge of improving our sleep quality and quantity can have a tremendous impact in our life satisfaction, our performance, and in our relationships. The next blog of this series will discuss how we sleep, specifically to understand REM and NREM, while also looking at how adolescents sleep differently.
Over time, humans have evolved to sleep slightly differently because of our busy lifestyles. Researchers who have studied human sleep patterns found that our ancestors slept in a biphasic pattern with 7-8 hours at one time during the night and then a 30-60 minute nap in the afternoon. Further, our ancestors used the sun to guide their sleep pattern. They went to bed when it got dark out (around 9pm) and awoke when it was light (around 6am). In our society today, most of us use a monophasic pattern of sleep, only sleeping once during the night and typically receiving less than 7 hours. We also have shifted our bedtimes to much later in the evening, sometimes working such long hours that our ancestors would already have been in bed. Most people still get up early to take on the challenges of the next day, resulting in less overall hours of sleep and no mid-day nap.
During sleep, scientists discovered that we experience two distinct phases, one where our eyes move rapidly under our eyelids (REM) and one where we have no eye movement (NREM). Throughout the night, NREM and REM switch back and forth in cycles. In the simplest terms, the first phase we hit during sleep is REM, before cycling into NREM stage 1 and 2 and then finally hit NREM stages 3 and 4, which are considered slow wave or deep sleep. Full cycles of sleep take approximately 90 minutes. Adults spend about 20 percent of their time in REM and the remaining 80% in NREM; however, the early night cycles are more predominantly NREM and the later ones REM. REM sleep is somewhat perplexing because why would we want such a light level of sleep, and why do our eyes get involved in the sleeping process? Researchers have found that REM sleep is what really makes us complex and interconnected humans. REM is responsible for helping us to navigate socioemotional signals including facial expressions and gestures, helps us to make thoughtful decisions, gives us the ability to regulate our emotions, and helps us build our emotional intelligence.
Sleep also changes across our lifespan. Adolescents have a particularly challenging time with sleep as there is a shift from more REM to NREM as their cognitive skills, reasoning, and critical thinking all starts to improve. But adolescents face difficulties in keeping up with the amount of sleep they need. “Adolescents face two harmful challenges in their struggle to obtain sufficient sleep as their brains continue to develop. The first is a change in their circadian rhythm. The second is early school times.” The circadian rhythm in adolescents is shifted to later in the evening so they are still at peak wakefulness when most adults are starting to get sleepy. This poses a challenge in getting them to go to sleep early and then also wake up early for school.
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