Every few years, statistics change regarding the optimal number of hours we should sleep. The average though (for adults) seems to fall between 7 and 9 hours. That said, approximately 70 million adults in the U.S. have some kind of sleep or wakefulness disorder. Many biological processes happen during sleep:
- The brain stores new information and gets rid of toxic waste.
- Nerve cells communicate and reorganize, which supports healthy brain function.
- The body repairs cells, restores energy, and releases molecules like hormones and proteins.
These processes are critical for our overall health. Without them, our bodies can’t function correctly.
Sleep allows cells to repair and regrow. This is supported by many important processes that happen during sleep, including:
- muscle repair
- protein synthesis
- tissue growth
- hormone release
When you sleep, your brain’s glymphatic (waste clearance) system clears out waste from the central nervous system. It removes toxic byproducts from your brain, which build up throughout the day. This allows your brain to work well when you wake up.
Research suggests that sleep contributes to memory function by converting short-term memories into long-term memories, as well as by erasing, or forgetting, unneeded information that might otherwise clutter the nervous system.
Sleep affects many aspects of brain function, including:
Sleep Quality Affects Our Emotional well-being
Areas of the brain in which sleep increases activity include:
One example of how sleep can help regulate emotion occurs in the amygdala. This part of the brain, located in the temporal lobe, is in charge of the fear response. It’s what controls your reaction when you face a perceived threat, like a stressful situation.
When you get enough sleep, the amygdala can respond in a more adaptive way. But if you’re sleep-deprived, the amygdala is more likely to overreact.
Two internal biological mechanisms–circadian rhythm and homeostasis–work together to regulate when you are awake and sleep.
Circadian rhythms direct a wide variety of functions from daily fluctuations in wakefulness to body temperature, metabolism, and the release of hormones. They control your timing of sleep and cause you to be sleepy at night and your tendency to wake in the morning without an alarm. Your body’s biological clock, which is based on a roughly 24-hour day, controls most circadian rhythms. Circadian rhythms synchronize with environmental cues (light, temperature) about the actual time of day, but they continue even in the absence of cues.
Sleep-wake homeostasis keeps track of your need for sleep. The homeostatic sleep drive reminds the body to sleep after a certain time and regulates sleep intensity. This sleep drive gets stronger every hour you are awake and causes you to sleep longer and more deeply after a period of sleep deprivation.
Factors that influence your sleep-wake needs include medical conditions, medications, stress, sleep environment, and what you eat and drink. Perhaps the greatest influence is the exposure to light. Specialized cells in the retinas of your eyes process light and tell the brain whether it is day or night and can advance or delay our sleep-wake cycle. Exposure to light can make it difficult to fall asleep and return to sleep when awakened.
Night shift workers often have trouble falling asleep when they go to bed, and also have trouble staying awake at work because their natural circadian rhythm and sleep-wake cycle is disrupted. In the case of jet lag, circadian rhythms become out of sync with the time of day when people fly to a different time zone, creating a mismatch between their internal clock and the actual clock.
How we respond to feeling tired
Think about what happens when we get tired. For most of us, our reserves of patience, tolerance, discipline, resilience, and energy are dangerously low. We’re less aware, more likely to miss important signs, and make mistakes. Humorously, an Australian study found that after 24 hours of wakefulness, we’re as cognitively impaired as an individual with a Blood Alcohol Content of .15 (twice the legal limit for driving).
When we’re tired we should sleep but…most of us don’t. Even though we may be passively lounging while we’re watching TV, scrolling through Facebook, reading, or engaged in hobby work, we’re resting, but we’re not sleeping. Our bodies need sleep to restore optimal functioning. Importantly, we lose weight when we’re sleeping!
For most of us, our natural circadian rhythm (regulated by the hormones cortisol and melatonin) is a relatively predictable 24-hour cycle. Some of us function more efficiently early in the cycle; others hit their stride later in the day. Either way, knowing our unique pattern of highs and lows is important to weight management.
This graph illustrates the onset, peak, and decline of two important hormones; cortisol and melatonin, the sleep hormone.
Cortisol, the stress hormone, provides us with natural energy and motivation to wake up, get up, eat, and focus on tasks that demand sustained attention. In this diagram the onset of cortisol is around 5 AM with a dramatic increase through 9 AM. As we near lunch time, we’re clearly on the downhill decline. This decrease explains in part, why some us start nodding off and craving an afternoon nap. From 3 PM levels decrease further until around 3 AM when the cycle begins again. When we look at the light-colored line representing melatonin levels; we see the opposite cycle. At 5 AM, while cortisol is increasing rapidly; melatonin is falling to its lowest state. It’s not until 6 PM that we see melatonin levels begin to increase and then peak between the hours of 10 PM and 3 AM. Bear in mind, this is an average cycle that’s highly influenced by our light/dark environmental cues and other physiological factors.
When we disregard our natural cycle, Brian gets annoyed and pouts. At times. Brian’s acts like a teenager. He takes the position that if you won’t let him sleep; you have to feed him what he likes best: Sugar! Here’s the scary reality. All day long, Brian ensures that with no cognitive exertion on OUR part; we walk, talk and breathe (sometimes drive) with little conscious effort or awareness. So… when he’s tired he can hijack your limbs, and before you know it, you’ll have made a trip to the kitchen and returned with a half-dozen cookies and a glass of milk. Think about it; how many times do you find yourself cupboard hopping or fridge surfing late at night? All day long you had the discipline to avoid temptation and now at the very worst time, you’re consuming a day’s worth of calories in minutes.
When our energy reserves are depleted, we’re more likely to reach for energy-dense foods and our ability to control how much we eat is diminished as well. So…when we realize we’ve blown our calories through the roof do we go to bed? Some of us might – but for the rest of us – a relapse on tasty treats only increases our cravings for more, and we reach for that second bowl of ice cream.
In session Six we discuss techniques for falling asleep and quieting the mind for restorative rest.
Your health care provider may recommend a polysomnogram or other test to diagnose a sleep disorder. A polysomnogram typically involves spending the night at a sleep lab or sleep center. It records your breathing, oxygen levels, eye and limb movements, heart rate, and brain waves throughout the night. Your sleep is also video and audio recorded. The data can help a sleep specialist determine if you are reaching and proceeding properly through the various sleep stages. Results may be used to develop a treatment plan or determine if further tests are needed.
Tracking Sleep Through Smart Technology
Millions of people are using smartphone apps, bedside monitors, and wearable items (including bracelets, smart watches, and headbands) to informally collect and analyze data about their sleep. Smart technology can record sounds and movement during sleep, journal hours slept, and monitor heart beat and respiration. Using a companion app, data from some devices can be synced to a smartphone or tablet, or uploaded to a PC. Other apps and devices make white noise, produce light that stimulates melatonin production, and use gentle vibrations to help us sleep and wake.
Tips for Getting a Good Night’s Sleep
Getting enough sleep is good for your health. Here are a few tips to improve your sleep:
Set a schedule – go to bed and wake up at the same time each day.
Exercise 20 to 30 minutes a day but no later than a few hours before going to bed.
Avoid caffeine and nicotine late in the day and alcoholic drinks before bed.
Relax before bed – try a warm bath, reading, or another relaxing routine.
Create a room for sleep – avoid bright lights and loud sounds, keep the room at a comfortable temperature, and don’t watch TV or have a computer in your bedroom.
Don’t lie in bed awake. If you can’t get to sleep, do something else, like reading or listening to music, until you feel tired.
See a doctor if you have a problem sleeping or if you feel unusually tired during the day. Most sleep disorders can be treated effectively. For more information see: [NIH: National Institute of Neurological Disorders and Stroke; NIH Publication No. 17-3440c].