Why We Sleep – Matthew Walker
Unlocking the Power of Sleep and Dreams
Sleep is The Fourth Biological Drive
There are two main reasons we go to sleep:
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Circadian rhythm: Every living creature on the planet has some sort of sleep-wake cycle
Sleep pressure: Every second you’re awake, a chemical called adenosine is building up in your brain. The concentration of this substance is increasing your desire to sleep
We Cycle Through Two Distinct Types Of Sleep
There are two stages of sleep:
Rapid Eye Movement (REM): The brain activity during REM is almost identical to when we’re awake. In this stage, we dream.
Non-rapid Eye Movement (NREM): A dreamless sleep During this stage, we’re calm and relaxed, and the heart rate is slow and regular. NREM sleep has four sub-stages: stages 1 through 4, with stage 4 being the deepest form of sleep.
Cycles of Sleep
Each cycle lasts around 90 minutes with different NREM/REM ratios:
Cycle 1: NREM (80%) -> REM (20%)
Cycle 2: NREM (70%) -> REM (30%)
Cycle 3: NREM (60%) -> REM (40%)
Cycle 4: NREM (50%) -> REM (50%)
Cycle 5: NREM (40%) -> REM (60%)
Interesting facts about sleep
The brain paralyzes our body during REM sleep to prevent us from acting on our dreams.
Sleeping aids our progress. When we stop learning or practicing something, our brain continues to work on it in the background. When we close our eyes, this passive learning process intensifies.
Sleep fuels our creativity. During sleep, our brains build connections, nurturing our problem-solving skills and imagination.
The main function of dreaming is to help us resolve past or current emotional problems.
There is this thing called lucid dreaming, where you’re completely aware of what you’re dreaming. In this state, you can manipulate the dream and decide what to do instead of simply going with the flow of the dream.
Because the temperature drops when the sun sets, and we slept in the wilderness for thousands of years, you’ll sleep better in a colder room.
Alarming facts about not sleeping
Consuming alcohol to induce sleep is a bad practice. Alcoholic beverages mess up your REM sleep, and you get fragmented sleep.
With age, our sleep efficiency declines. This is mainly because of our frequent visits to the bathroom. A simple fix would be to reduce the intake of fluids before going to sleep.
Studies confirm that a lack of sleep can lead to a lot of nasty outcomes: diabetes, depression, chronic pain, stroke, cardiovascular disease, and Alzheimer’s disease.
You can’t sleep it off. Even if you get enough sleep to recover from last night’s party, the brain cells that died during the sleep deprivation will never heal.