What You Should Know About Sleep Cycles & Their Impact on Your Health

Sleep Cycle Explained: A Journey Through the Stages

Sleep is a cyclical journey. At night, the body moves through various stages of sleep multiple times, each lasting about 90 minutes. Brain activity, heart rate, breathing, and muscle tone changes characterize these cycles. 

There are two main phases of sleep cycle​: Non-rapid eye movement (NREM) and rapid eye movement (REM) sleep.

1. Non-Rapid Eye Movement (NREM) Sleep

There are three NREM sleep stages:

• Stage N1 (Light Sleep) is the transitional phase between wakefulness and sleep. This stage of sleep cycle​ typically lasts 1 to 7  minutes, about 5 to 10% of the sleep cycle. During N1, you're easily awakened and may experience slight muscle twitches. Your brain activity slows down, shifting from alpha to theta waves.

• Stage N2 (Deeper Sleep) marks a further slowing of brain activity, with the appearance of sleep spindles (bursts of brain activity) and K-complexes (large, slow brain waves).  Your body temperature drops, and heart rate and breathing become more regular. This stage lasts longer, usually around 20 minutes per cycle, and accounts for about 45-55% of total sleep.

• Stage N3 (Deep Sleep/Slow-Wave Sleep) is NREM sleep's deepest and longest-lasting stage. This stage’s sleep cycle length​ usually lasts 20 to 40 minutes and progressively shortens throughout the night. It typically accounts for about 15 to 25% of total sleep. Delta waves, the slowest brain waves, dominate your brain activity.

2. Rapid Eye Movement (REM) Sleep

REM sleep cycle is the stage of sleep where dreaming happens. Your brain activity increases during this time, almost like when you're awake. Your eyes move quickly under your closed eyelids, which is why it’s called “Rapid Eye Movement.” Your heart rate and breathing become irregular, and your blood pressure increases. Interestingly, your muscles are paralyzed during REM sleep, which stops you from acting out your dreams.

What’s The Importance of Sleep for Health​

The stages of sleep are not just arbitrary divisions; they each contribute significantly to our overall health and well-being.

• Physical Restoration

Deep sleep is vital for physical repair and growth. During this stage, the body releases growth hormones essential for cell regeneration and muscle repair. These hormones also play a crucial role in strengthening the immune system.

• Cognitive Function

The importance of sleep to cognitive health is important. REM sleep is essential for memory consolidation, learning, and problem-solving. During this time, the brain processes and organizes information gathered throughout the day, enhancing cognitive flexibility and strengthening neural connections.

• Emotional Regulation

Good sleep promotes emotional stability and resilience. Sleep deprivation can significantly impact mood and emotional regulation, which leads to irritability, anxiety, and difficulty managing stress.

• Hormonal Balance

Sleep is crucial for regulating various hormones related to appetite, metabolism, and stress response. Disrupted sleep can lead to hormonal imbalances, increasing the risk of chronic diseases.

What Affects Your Sleep?

There are several factors that can influence the quality and duration of your sleep, impacting the progression through the different sleep stages. 

1. Age: Sleep patterns change as we age. Newborns sleep 16 to 18 hours per day discontinuously, while older adults may experience changes in sleep architecture, including lighter sleep and more frequent awakenings.
   
   
2. Lifestyle Factors: Consuming caffeine and alcohol incredibly close to bedtime can disrupt sleep. Intense exercise too close to bedtime can also have the opposite effect.
   
   
3. Environment: A comfortable sleep environment is essential. This includes a dark, quiet, and cool bedroom. Noise, light, and temperature fluctuations can disrupt sleep cycles.
   
   
4. Stress: High cortisol levels can make falling asleep difficult, and chronic stress can lead to significant sleep problems.
   
   
5. Underlying Health Conditions: Sleep apnea, restless leg syndrome, chronic pain, and other medical conditions can significantly impact sleep quality and disrupt sleep stages. Anxiety and depression are also closely linked to sleep disturbances.
   
   
6. Medications: Medications can have side effects that affect sleep or alter the sleep cycle.
   
   
7. Technology Use: The blue light from smartphones and tablets can disrupt melatonin production, a sleep-regulating hormone, making it harder to fall asleep.

What Happens When You Lack Quality Sleep?

Poor sleep—whether in duration or quality—takes a toll on both body and mind, with consequences ranging from minor to life-altering. Here's a look at some of the health effects of sleep deprivation​ that can reduce your lifespan:

• Daytime Fatigue and Sleepiness: Sleep deprivation leads to feelings of tiredness and sluggishness, hindering concentration and productivity. 
• Cognitive Impairment: Insufficient sleep negatively impacts memory, problem-solving, and decision-making abilities, which leads to decreased alertness and slower reaction times.   
• Mood Disturbances: Sleep deprivation and mental health do not mix well. Lack of sufficient sleep can adversely affect mood, leading to irritability, anxiety, and emotional instability.
• Weakened Immune System: During sleep, the body produces cytokines, which help fight inflammation and infection. Lack of sleep weakens the immune system, making you more vulnerable to illness.   
• Increased Risk of Chronic Diseases: Studies show that people who do not get enough sleep are at higher risk of hypertension, diabetes, obesity, depression, heart attack, and stroke—long-term effects of sleep deprivation and sleep disorders.  
• Weight Gain: Disrupted sleep can alter appetite-regulating hormones, leading to increased cravings and reduced physical activity. 
• Hormonal Imbalances: Insufficient sleep interferes with the regulation of essential hormones, such as cortisol (the stress hormone), insulin, growth hormone, and reproductive hormones.
• Sleep Disorders: A decline in sleep quality can trigger a cascade of health issues, such as insomnia and sleep apnea, ultimately affecting overall health.

Tips for Improving Your Sleep Cycles

Studies show that an estimated 50 to 70 million Americans chronically suffer from sleep and wakefulness disorders. These disorders hinder daily functioning and adversely affect health and longevity. By adopting these simple yet effective sleep strategies, you can enhance the quality of your sleep and wake up feeling refreshed.

Establish a Regular Sleep Schedule

To regulate your body's natural sleep-wake cycle, go to bed and wake up simultaneously each day, even on weekends.

Create a Relaxing Bedtime Routine

Engage in calming activities such as reading a book, soaking in a warm bath, or practicing relaxation techniques like deep breathing or meditation.

Optimize Your Sleep Environment

Ensure your bedroom is dark, quiet, and cool.  Invest in a comfortable mattress and pillows.

Avoid Caffeine and Alcohol Before Bed

These substances can interfere with sleep quality.

Get Regular Exercise

While regular physical activity benefits sleep quality, avoiding exercising too close to bedtime is best.

Manage Stress

Poor sleep quality can increase cortisol levels. Practice stress management techniques like meditation or yoga.

Get Your Sleep Biomarkers Checked

Consider getting biomarkers of sleep deprivation tested to gain insight into your sleep health. Essential assessment factors include thyroid stimulating hormones, cortisol levels, and HbA1c (Glycated Hemoglobin). These tests can help identify underlying issues affecting your sleep quality, such as hormonal imbalances or metabolic disorders.

Mito Health: Your Partner in Optimizing Sleep

At Mito Health, we understand that a healthy sleep cycle is a cornerstone of well-being. We offer flagship blood panels and advanced health tests to help you understand your sleep biomarkers. Join Mito Health and get a comprehensive understanding of your sleep health, biomarkers, and more.

The Key Takeaway

Prioritizing quality sleep is vital for our overall physical and mental well-being. Understanding the distinct stages of sleep—NREM and REM—highlights the importance of each phase in recovery, memory consolidation, and overall health longevity. To enhance sleep quality, establish a consistent sleep schedule, cultivate a soothing bedtime routine, and be mindful of lifestyle choices such as caffeine and alcohol consumption. 

Additionally, a check-up on your sleep biomarkers may help identify underlying issues affecting your sleep. By taking these steps, we can improve our sleep, overall health, and quality of life.