I don’t know how many times I command the alarm some mornings. Do you ever feel like you’re not getting enough sleep? Perhaps you aren’t!
The average American and Australian today sleep fewer than seven hours a night, a decrease of about two hours from a century ago. Nine hours were too much, in the opinion of Thomas Edison, who helped change our sleep habits when he brought light bulbs into our nights.
He actually said, “Sleep is an absurdity, a bad habit” and announced that people who slept when darkness fell were “far less intelligent” than those who turned on lights to continue working. Sleep was a waste of time, he thought, so Edison focused on creating the light bulb.
And it worked. According to the US Centers for Disease Control, around 70 million American adults are chronically sleep deprived, snoozing less than the recommended minimum of about seven hours a night.
Caffeine binds to the same brain receptors as adenosine, a natural compound that signals your brain to prepare for sleep. This explains why drinking coffee at night can keep you awake.
Indeed, we are proud of our sleeplessness. Dr. Matthew Walker, author of Why We Sleep and professor of neuroscience and psychology at the University of California, Berkley, says, “People have this . . . braggadocio about how little sleep they are getting. Everyone is desperate to seem busy because we equate busyness with importance.”
Edison was, it turns out, dead wrong. Current research shows just how much we need our sleep and what happens if we don’t get enough.
In fact, our need for sleep is by design. According to our Creator’s own written Word (Psalm 127:2), sleep is actually a precious gift from him . . . and not just on those days when we don’t have to rise with the alarm!
What Is Sleep?
The Bible doesn’t say much about the specific purposes of sleep beyond our need for rest and as a euphemism for death. Yet it reminds us that God, the ultimate engineer who created our complex, amazing bodies, also planned from the very beginning an efficient system for our bodies and brains to rest from their labors and recuperate.
Genesis tells us that God created most of the universe to run in a cycle. The earth cycles around the sun to create the year. The earth spins on a cycle to create days. Just as days, months, seasons, and years go in cycles of darkness, rest, and reenergization, so do our bodies.
Long before humans learned to tell time, God wired into our bodies a biological clock to take advantage of the different times of day and night.
Long before humans learned to tell time, God wired into our bodies a biological clock to take advantage of the different times of day and night. This “clock” is basically a 24-hour repeating rhythm called the circadian rhythm (to learn more, see Answers magazine, Sept.–Oct. 2018, p. 64). These internal clocks can be traced down to the genetic level, as cells have individual “clock genes” so they can adapt to changing needs throughout the day. Overseeing them all is a small region in the brain’s hypothalamus called the suprachiasmatic nucleus (SCN). This body clock releases chemicals into your body in a daily rhythm.
So how does sleep fit into this rhythm?
During your waking hours, a compound called adenosine, a byproduct of energy consumption, accumulates in several key locations in the brain. As adenosine increases, it signals your brain to prepare the body for sleep. During sleep your brain’s cells break down the adenosine. If you don’t get enough sleep, too much adenosine remains, making you feel tired when you wake up.
Though humans sleep less than most animals, our sleep is more efficient—we spend less time in light stages of sleep and more in deeper stages. Our REM stage makes up 25% of our sleep, compared to 5% in primates.
Melatonin is a pillow pal of adenosine. When daylight begins fading, your eyes notify the brain, and the pineal gland at the base of your brain starts to pump melatonin into your bloodstream. As the melatonin increases, it signals your body that it’s time for sleep, and it helps you feel drowsy. When morning arrives and the retina detects light, it signals the brain to slow down the release of melatonin. Even the smallest amount of light can reduce the production of melatonin and start to wake us up. You see why we can blame Edison for some of our sleep problems!
Lights Out! Time to Party!
Once upon a time, people thought when we sleep, our brains basically go inactive. Mistake! When the lights go out, it’s party time for the brain!
Around 86 billion neurons—the brain cells that transmit information to other nerve cells, muscles, or glands—get busy communicating through electrical and chemical signals. Meanwhile, our sensory receptors that help us keep in touch with the surrounding environment shut down. The transition to deep sleep occurs in three stages.
33% of dreams contain bizarre elements impossible in everyday life.
The first is called Stage 1. This shallow end of sleep usually lasts around five minutes, and if people wake up at this initial stage, they may not even realize they’ve been asleep. Sleepers may feel muscle jerks or a falling sensation.
As we enter Stage 2 of sleep, the brain comes alive. A series of half-second electric sparks, called spindles, start to zap the cerebral cortex, the gray matter that covers the outer layer of the brain, where language and consciousness are based.
As these spindles stimulate the cortex, this part of the brain preserves information we’ve recently acquired. It might also link this new information to existing memories. The more spindles that fire up at night, the more likely we are to do well at new tasks the next day.
While awake, the brain is optimized to collect external stimuli, but the sleeping brain consolidates that information. It moves from a recording mode into an editing mode, analyzing the information to decide which memories to keep and which to delete. A 2011 study published in the Journal of Neuroscience found that the brain’s prefrontal cortex appears to tag memories that may be important or useful for the future, while the hippocampus consolidates those memories during sleep.
Your Sleepless Brain
Your brain never quits. It simply takes on new jobs at night that prepare you for the new day. While awake, the brain is optimized to collect external stimuli, but during sleep the brain consolidates that information.
- The SUPRACHIASMATIC NUCLEUS, a small region in the hypothalamus, oversees the body clocks that release chemicals to keep the body in a 24-hour rhythm of day and night.
- The CEREBRAL CORTEX, the gray matter that covers the brain’s outer layer, lights up as we enter sleep. Electric sparks, called spindles, stimulate the cortex where language and consciousness are based, preserving information we’ve recently acquired.
- The PREFRONTAL CORTEX analyzes memories from the day to decide which to keep or delete, making room for the next day.
- The HIPPOCAMPUS consolidates memories from the past day that the prefrontal cortex has tagged as useful.
- The BRAINSTEM regulates REM sleep, when our most vivid dreams occur. During REM sleep, the brain strengthens connections between neurons to store the previous day’s information in long-term memory.
The busy activities of Stage 2 can fill almost an hour of the first 90-minute sleep cycle. The spindle fireworks explode every few seconds for a while, but as they taper off, our heart rate slows and our body temperature drops. We’re literally out cold as we sink into deeper sleep and lose all ability to notice anything going on around us.
If something disturbing happens, it’s best not to fall asleep right away. If we sleep before an ordeal is mentally resolved—such as soldiers returning from difficult missions—researchers have found that the experience and its trauma may be lodged more deeply in longterm memory. It’s best to get a few hours distance between the trauma and sleep, to allow sensory receptors to absorb other stimuli.
Thomas Scammell, a neurology professor at Harvard Medical School, explains why it’s so valuable to shut down our senses. “Being awake is demanding. You’ve got to go out there and outcompete every other organism to survive, and the consequences are that you need a period of rest to help cells recuperate.”
We may not agree with Scammell’s evolutionary stance of survival of the fittest, but he has a point: being awake is certainly demanding. During Stage 3 we respond even less to interruptions than we did in Stage 2. Since the spindles have decreased, our body starts to produce slow, deep brain waves called delta waves, similar to those produced by coma patients. These waves increase as we move deeper into our sleep cycle. We don’t dream during Stage 3, and we may not even be able to feel pain, though night terrors (intense feelings of fear and screaming) can occur.
While we are in this relaxed state, our brains and bodies remain at work. While we’re awake, our neurons are packed together; but during sleep, brain cells apparently deflate by up to 60%, widening the spaces between them. Studies of mice indicate that the cells dump their metabolic waste into these spaces, including beta-amyloid, a toxic chemical that hinders communication between neurons and is linked to Alzheimer’s. During sleep, spinal fluid then sloshes through these passageways in the brain, taking the toxins with it.
Giulio Tononi, at the University of Wisconsin–Madison, has suggested that another major function of sleep is to “reset” the connections between our neurons, called synapses. This would keep our brains from becoming overloaded with new memories, like too many appliances plugged into an outlet. That gives us room to make fresh memories and learn new information the next day. Studies of mice in 2017 provided indirect evidence: their synapses shrank nearly 20% during sleep.
Also during deep sleep, cells make repairs, and the brain ramps up the production of growth hormones, which we need throughout life to rebuild bones and muscles.
How to Get the Best Sleep
Chronic sleep disorders afflict up to 70 million Americans, and it’s not just an American problem. Having sleeping trouble? Studies suggest some helpful tips:
- Be consistent. We function best when our bodies follow a regular sleeping schedule. Go to bed and get up around the same time each day, even on weekends.
- Keep your room slightly cool. Heat can hinder sleep, especially if you have a soft mattress.
- Turn out the lights. Remember, light affects melatonin levels, which prepare our body for sleep. Even turn off night lights and purchase black-out curtains.
- Get more sunlight. Not enough light during the day can disrupt sleep just as extra light at night can.
- Turn off electronic devices an hour or two before bedtime. Artificial lights can significantly lower melatonin (important for sleep) and stimulate brain activity.
- Cut out late-day caffeine. It binds to the same brain receptors as adenosine, preventing that chemical from helping our bodies prepare for sleep.
- Consider a light dinner no closer than three hours before bedtime. Eating before bedtime can keep you awake (remember, food is energy).
- Reserve your bed just for sleeping. Watching videos, working, or reading in bed can make it harder for your body to transition to sleep.
- Exercise well during the day. It relieves stress. But don’t exercise within three hours before bedtime because it makes you energetic.
- Avoid daytime naps, no matter how tired you are. Naps can disrupt the natural cycle.
The Eyes Have It!
These three stages of sleep are usually categorized together in a grouping called Non-REM or NREM sleep. REM stands for Rapid Eye Movement. While we’re in the three stages of NREM sleep, our eyes remain primarily relaxed. But when we hit this really deep sleep, called REM sleep, our eyes come alive.
Around 90 minutes after falling asleep, we move into our first round of REM sleep. Each night our bodies actually go through about four to five sleep cycles, going back to Stages 1–3 and then back to REM. The REM stage gets longer each time, and the NREM 3 stage gets shorter. The final REM sleep cycle can last up to an hour. We spend about 20–25% of our sleeping time in REM sleep.
REM sleep is regulated by the brainstem, a different part of the brain from the parts controlling NREM sleep.
Researchers are finding that artificial lights can keep us awake at night. They significantly lower levels of melatonin, a hormone that signals our bodies to sleep. For example, two hours of exposure to a tablet can reduce melatonin levels 22%.
REM sleep is vital for our mental well-being. If we’re awakened as we’re drifting into REM sleep and aren’t allowed to enter that stage, researchers found we’re likely to experience increased tension, anxiety, depression, difficulty concentrating, lack of coordination, weight gain, and a tendency to hallucinate.
As we move into REM sleep, our body’s muscles fall into a stage of near-paralysis, only moving occasionally. Our eyes move rapidly beneath closed eyelids, similar to the way they do when we’re awake. Scientists have not pinpointed why the eye movement occurs, although it may be linked with dreaming.
Our body temperature also drops, and our heart rate and respiration speed up. We also take in more oxygen as our breathing becomes fast and shallow. Some experts say that during REM sleep the brain may be even more active than it is during wakefulness. According to the National Sleep Foundation, during REM sleep the brain processes information from the day to store it in the long-term memory.
Oh, the Places You’ll Go!
Dreams can occur any time during sleep, but the most vivid ones occur during deep REM sleep, when the brain is most active.
Sigmund Freud, the famous psychoanalyst, believed dreams revealed a person’s unconscious thoughts. That probably isn’t true, most scientists say. Some researchers say our dreams are just a side effect of brain activity, that the brain activity is more important than the actual dreams. While dreaming, the brain reshapes itself by rewiring and strengthening connections between neurons. According to the authors of How Your Brain Works, dreams help us consolidate our memories, to make sense of our new experiences, process them, and keep our emotions in check—another gift from sleep which keeps us from becoming emotionally overwhelmed.
An Unwrapped Gift
A gift is meant for our blessing, and if we neglect a gift like sleep, we do so at our own peril. “Every single disease that is killing us in the developed world has significant and many causal links to insufficient sleep,” concludes Matthew Walker, the author of Why We Sleep.
Decision-making, problem-solving, focusing, balance when you walk, reaction time—all these things are inhibited by lack of sleep. No wonder inadequate sleep contributes to hundreds of thousands of accidents each year—including 6,000 annual fatalities caused by drowsy driving.
Not getting enough sleep is also connected to many other tragic health problems. If you are sleep deprived, for instance, you’re 33% more likely to face dementia. Your immune system weakens, so you’re three times as likely to catch a cold. Risk for colorectal cancer increases 36%. Sleep-deprived folks have three times the risk of becoming diabetic than their sleeping counterparts (sleeplessness affects the body’s release of insulin). You have a 50% higher risk of becoming obese (the chemicals that signal hunger get out of whack). You’re 48% more likely to develop heart disease (your blood pressure base gets higher). And the list goes on.
It only makes sense that God made our bodies and their cycles to work together so precisely for our optimum health. And when sleep gets out of sync, we should go back to our Creator to put everything back in balance. “It is in vain that you rise up early and go late to rest, eating the bread of anxious toil; for he gives to his beloved sleep” (Psalm 127:2). Our Creator wants us to rely on him to give us strength to complete the tasks he has for us while it’s day, but when it’s time to sleep we need to take our rest, displaying our faith in him.
As Solomon—the classic example of a workaholic—tells us in Ecclesiastes 5:12, “Sweet is the sleep of a laborer.” At the end of a long, hard day, God gives us the gift of sweet, refreshing sleep. He wants us to view our lives that way, too. We should devote ourselves to the Lord’s work while it’s day, but when the day is over, he promises us eternal rest, or “sleep.”