Don’t Sleep on This , part deux
Don’t Sleep on This, part deux
Hello, people, welcome back to the blog! Last week, we started a new series on sleep, and talked about some of the theories on why we sleep and what it does for us. This week, we’re going to talk about what induces sleep, the stages of sleep, what’s happening in your brain and body while you’re sleeping, and what can happen when sleep is disrupted.
As I mentioned last week, our bodies regulate sleep in much the same way that they regulate eating, drinking, and breathing, and this is indicative of the critical role sleep plays in our health and well-being. But why do we get sleepy? What tells us when it’s bedtime? Each person has an internal “body clock” that regulates his or her sleep cycle, controlling when they feel tired and ready for bed, versus refreshed and alert. This clock operates on a 24-hour cycle known as the circadian rhythm.
After waking up from sleep in the morning, you become increasingly tired throughout the day as it progresses. These feelings will generally peak in the evening leading up to bedtime. This sleep drive- also known as sleep-wake homeostasis- appears to be linked to adenosine, an organic compound produced in the brain. I mentioned adenosine last week. It builds up throughout the day as you become more tired, and then the body breaks it down during sleep to dispose of.
Light influences the circadian rhythm. The brain contains a special region of nerve cells known as the hypothalamus, and a cluster of cells within it called the suprachiasmatic nucleus, which processes signals when the eyes are exposed to natural or artificial light. These signals help the brain determine whether it is day or night, time to be awake, or time to sleep. As natural light disappears in the evening, the body releases melatonin, a hormone that induces drowsiness. And when the sun rises in the morning, the body will release the hormone cortisol, which promotes energy and alertness. This influence that light has on the brain cannot be underestimated, especially blue light from devices. This is the reason why I always tell patients no screen time on devices right before bed. Blue light exposure just before you want to go to sleep is a surefire way to foul up your sleep cycle. I’ll get more into that in a later blog in this series.
The Sleep Cycle
As you sleep, your brain cycles through four stages of sleep. Stages 1 to 3 are considered non-rapid eye movement (NREM) sleep, also known as quiet sleep, while stage 4 is rapid eye movement (REM) sleep, also known as active sleep or paradoxical sleep. These stages occur multiple times throughout the night, with a full sleep cycle generally lasting about 90 to 110 minutes. The stages are repeated four to five times during a 7 to 9 hour sleep period, with each successive REM stage increasing in duration and depth of sleep.
Each stage has a unique function and role in maintaining your brain’s overall cognitive performance, while some stages are also associated with physical repairs that keep you healthy and get you ready for the next day. Fun fact: there used to be five stages of sleep, but this was changed by the American Academy of Sleep Medicine several years ago.
During the earliest phases of sleep, you’re still relatively awake and alert. During this time, the brain produces what are known as beta waves, which are small, fast brain waves that mean the brain is active and engaged. As the brain begins to relax and slow down, it lights up with alpha waves. During this transition, you may experience strange and vivid sensations, which are known as hypnagogic hallucinations. Common examples of hypnagogic hallucinations include the sensation of falling or of hearing someone call your name. There’s also the myoclonic jerk. No, I’m not referring to the person lying next to you… Ever gone to bed and felt like you’re just about to drift off and then BAM… you’re suddenly startled awake for seemingly no reason at all? That’s a myoclonic jerk.
NREM Stage 1
This first stage of the sleep cycle is a transition period between wakefulness and sleep that typically lasts for around 5 to 10 minutes. During this time, the brain is still fairly active and producing high amplitude theta waves, which are slow brain waves that mainly occur in the frontal lobe of the brain. During this stage, your brain slows down, while your heartbeat, eye movements, and breathing slow with it. During this stage, your body relaxes, but your muscles may twitch.
NREM Stage 2
According to the American Sleep Foundation, people spend approximately 50% of their total sleep time during this stage, which lasts for about 20 minutes per cycle. During this stage, your body prepares for deep sleep. You become less aware of your surroundings, your body temperature drops, eye movements stop, and your breathing and heart rate become more regular. The brain also begins to produce sleep spindles, which are bursts of rapid, rhythmic brain waves that are thought to be a feature of memory consolidation, when your brain gathers, processes, and filters the new memories you acquired the previous day.
NREM Stage 3
This stage is when the brain and body repairs, restores, and resets for the coming day, so getting enough NREM stage 3 sleep is essential to feel refreshed the next day. During this stage, which lasts between 20 to 40 minutes, deep, slow brain waves known as delta waves begin to emerge, so this is sometimes called the delta sleep stage. This is a period of deep sleep where any noises or activity in the environment often fail to wake the sleeping person. During this stage, your muscles are completely relaxed, your blood pressure drops and breathing slows, and you progress into your deepest sleep. It’s during this deep sleep stage that your body starts its physical repairs: cells repair and rebuild, hormones are secreted to promote bone and muscle growth, and your body produces elements to strengthen your immunity to fight off illness and infection. During this stage, your brain is still busy too- it’s consolidating declarative memories, general knowledge, personal experiences, facts and statistics, and other things you have learned that day.
REM Sleep Stage 4
The fourth stage of REM sleep begins roughly 90 minutes after falling asleep. During this time, your brain lights up with activity, your body is relaxed and immobilized, your breathing is faster and irregular, your eyes move rapidly, and you dream. It’s during this stage that your brain’s activity most closely resembles its activity during waking hours, but your body is temporarily paralyzed. That’s a good thing, as it prevents you from acting out your dreams. Memory consolidation also happens during REM sleep, but it’s more about emotions and emotional memories being processed and stored. Your brain also uses this time to permanently cement information into memory, making it an important stage for learning.
I should note that sleep doesn’t progress through the four stages in perfect sequence. When you have a full night of uninterrupted sleep, the stages usually progress as follows:
Sleep begins with NREM stage 1 sleep.
NREM stage 1 progresses into NREM stage 2, followed by NREM stage 3. NREM stage 2 is then repeated, and then finally REM sleep. Once REM sleep is over, the body usually returns to NREM stage 2 before beginning the cycle all over again. The amount of time spent in each stage changes throughout the night as the cycle repeats. A person’s “sleep architecture” is the term used to refer to the exact cycles and stages a person experiences in a night. If you see a sleep specialist for any issues, they often do a sleep study, and will then show you your sleep architecture on what’s known as a hypnogram, a graph produced by an EEG during a sleep study.
There are any number of issues that can interrupt your sleep cycles, causing stages to be cut short and cycles to repeat before finishing. Depending on the culprit, it can happen occasionally or on a chronic basis. Any time you have trouble falling asleep or staying asleep at night, your sleep cycle will be affected. Some factors that may affect your sleep stages and that are commonly associated with interrupted sleep include:
Age: As you age, sleep naturally becomes lighter and you are more easily awoken.
Nocturia: Frequently waking up with the need to urinate. This is big for older men due to prostate issues.
Sleep disorders, including obstructive sleep apnea, when breathing stops and starts during sleep, and restless leg syndrome, a strong sensation of needing to move the legs
Pain: Difficulty falling or staying asleep due to acute or chronic pain conditions, like fibromyalgia
Mood disorders such as depression and bipolar disorder
Other health conditions, including Alzheimer’s disease, Parkinson’s disease, obesity, heart disease, and asthma
Lifestyle habits: Getting little to no exercise, cigarette smoking, excessive caffeine intake, and excessive alcohol use all affect your ability to fall asleep and/ or stay asleep.
So how much sleep do you need? It varies a little from person to person, and it really depends on your age. The CDC suggests the following based on a 24 hour period:
From birth to 3 months: 14 to 17 hours, including naps
From 4 to 12 months: 12 to 16 hours, including naps
From 1 to 2 years: 11 to 14 hours, including naps
From 3 to 5 years: 10 to 13 hours, including naps
From 6 to 12 years: 9 to 12 hours
From 13 to 18 years: 8 to 10 hours
From 18 to 60 years: 7 or more hours
From 61 to 64 years: 7 to 9 hours
65 years and older: 7 to 8 hours
Most adults require between seven and nine hours of nightly sleep. Children and teenagers need substantially more sleep, particularly if they are younger than five years of age, as it is vital for their growth and development.
Work schedules, day-to-day stressors, a disruptive bedroom environment, and various medical conditions can all prevent us from receiving enough sleep. Over time, not getting enough sleep and not cycling through the four stages appropriately can cause any number of health issues, along with difficulty with learning and focusing, being creative, making rational decisions, problem solving, recalling memories or information, and controlling your emotions and behaviors. Keep in mind that it’s important not just to get seven to nine hours of sleep per night, but to ensure that it’s uninterrupted, quality sleep that allows your body to benefit from each of the four stages.
Without enough sleep, your body has a hard time functioning properly. Sleep deficiency is linked to chronic health problems affecting the heart, kidneys, blood, brain, and mental health. Lack of sleep is also associated with an increased risk of injury for both adults and children. In older adults, poor sleep is associated with an increased risk of falls and broken bones. Sleep deficit is even linked to an increased risk of early death. Driver drowsiness is a good example. Specific consequences of sleep deprivation can include mood changes, anxiety, depression, poor memory, poor focus and concentration, poor motor function, fatigue, weakened immune system, weight gain, high blood pressure, insulin resistance, and many chronic diseases, like diabetes and heart disease. The bottom line is that sleep keeps you healthy and functioning well. It lets your body and brain repair, restore, and re-energize.
If you experience any of the following issues, make an appointment to see your healthcare provider, as you may not be getting the sleep you need. They can help determine the underlying cause and improve the quality of your sleep.- If you are having trouble falling or staying asleep at least three nights per week- If you regularly wake up feeling unrested- If your daytime activities are affected by fatigue or issues with mental alertness- If you often need to take a nap to get through the day- If a sleep partner has told you that you snore or gasp when you are asleep- If lack of sleep is affecting your mental well-being
That’s a good place to stop, as next week, I’ll be talking about how sleep affects your mental well-being, and vice versa. I hope you enjoyed this blog and found it to be interesting and educational. Please feel free to share it with family and friends. Be sure to check out my YouTube channel with all of my videos, and I’d appreciate it if you would like, subscribe, leave comments, and share those vids! As always, my book Tales from the Couch has more educational topics and patient stories, and is available in office and on Amazon.
Thank you and be well people!