Not so long ago, our culture lionized folks who did not sleep — they seemed smarter, stronger, and more determined than the rest of us mere mortals. American heroes such as Thomas Edison, Thomas Jefferson, and Benjamin Franklin were probably “short sleepers,” people who thrived on six or less hours of sleep per night and therefore had a few more hours a day available for genius and action.
Mother (Nature) Knows Best
Today we know better. “If we didn’t need eight hours of sleep and could survive on six, Mother Nature would have done away with 25 percent of our sleep time millions of years ago,” neuroscientist and author Matthew Walker has explained on Hidden Brain.
Only about 2 percent of people have the genetic mutation that allows them to thrive on six or less hours a sleep per night. You can determine if you are one of those people if you take a genetic test.
The rest of us are just kidding ourselves. If you are like 98 percent of adults, you need between seven and nine hours of sleep a night. Individual needs within that range vary; most adults do best when we get between seven and eight hours of sleep and go through five or six complete sleep cycles. Many of us are sleep-deprived, and it’s damaging our health.
We now know that people are 13 percent more likely to die prematurely if they regularly get 6 or fewer hours of good sleep a night. In recent years, scientific studies have linked sleep deprivation to a hot mess of health problems, including high blood pressure, increased diabetes and heart disease risk, weight gain, poor balance, mood disorders, and memory issues.
What Each Stage Of Your Sleep Cycle Does For Your Health
Have you ever been drifting off to sleep and suddenly your whole body jerks? That’s Stage 1, the first 5 percent or so of each sleep cycle.
Stage 2 occupies between 45-55 percent of each cycle.Your breathing and heart rate slow and your body temperature decreases slightly.
If you wake up at night to go to the bathroom, it’s probably during Stage 1 or 2 of one of your sleep cycles. Similarly, if you have the luxury of “sleeping in” without being awakened by an alarm clock or some other nuisance, you will wake up during these stages.
Deep sleep begins during Stage 3 and transitions into Stage 4, which together make up about 20% of each sleep cycle. Breathing is very slow and relaxed, muscle activity is limited, and your brain slows down. When you are awake, your brain consumes a whopping 25 percent of your energy. During deep sleep, the brain activity becomes big, slow delta waves that don’t consume nearly as many resources. That means your body can devote more energy to parts other than your four-pound, hardworking brain. The blood supply to your muscles increases, tissue growth and repair occur, your energy is restored, and hormones are released. That’s why deep sleep is so crucial for health.
The fifth stage is REM (rapid eye movement). Brainwaves speed up from the delta stage. Your breathing is rapid and shallow. If you are awakened and remember a dream, you were likely in the REM stage of a sleep cycle, when dreams happen. Scientists don’t fully understand what happens during REM, but they know it’s essential for processing our memories and even safeguarding our mental health. (For a fascinating story about what happened to a man who went without REM for 11 days, check out this podcast episode.)
Your body does work during stages 3, 4 and 5 of sleep that it doesn’t do at any other time—it resets your enzymes and hormones, boosts the immune system, puts permanent memories in place, and clears away metabolic waste. During deep sleep, your brain sweeps itself of neurotoxins, “almost like a dishwasher,” one neuroscientist has explained. Scientists now suspect that deep sleep is crucial for reducing the risk of dementia.
If you’re not getting the deep sleep you need, your body can’t do this important work and your health suffers. Here’s how one neuroscientist explained it to me: “Imagine your body is a building and the janitorial staff need eight hours a night to clean it. One or two nights of working only six hours won’t have a noticeable effect. However, after several consecutive nights of six hour shifts, you’ll start to see dirt pile up in the corners.”
Sleep is one of the best things we can do for our health and, best of all, it’s totally free of charge. Yet many folks living in the developed world don’t get enough sleep. In my next post, I’ll share some simple hacks to help you improve your sleep and your health.