The Science of Sleep
by Dr. Jason Peñaranda
Medical Associate, Aegle Wellness Center
Sleep is an essential part of the maintenance of our health. We spend about a third of our lives sleeping. Science has come a long way from the view that sleep is just a matter of energy conservation and recharging, much like a battery. Though we still do not fully understand it, we now know that sleep is more complex. It’s a time of organization, processing, and physical restoration. It’s the time when our bodies assimilate the nutrients we extracted from digestion, move the wastes to the detox organs, repair the daily wear and tear of tissues and organs, and of course, rest.
Sleep influences all of our physiologic functions and overall quality of life. Conversely, these functions also affect the quality of our sleep.
The Circadian Rhythm
The Circadian Rhythm is the biological clock to which our physiological functions are attuned. It is dependent on the dynamics of day and night time. We are designed to sleep at a specific time when it’s dark, quiet, and cold and to be awake when it’s bright, noisy, and warm.
Source: UNC Eshelman School of Pharmacy
Age and Sleeping Patterns
As we age, our sleep patterns and requirements change. Newborns tend to have short and frequent sleep-wakefulness patterns, while children sleep earlier than adults. Adults wake up earlier and are much more alert when they wake up.
The Stages of Sleep
The stages of sleep are REM (rapid eye movement) sleep and NREM (non-REM) sleep. They are called such because of the characteristic rapid eye movement observed during the REM stage. NREM itself has 3 stages (N1, N2, N3); it used to be classified with a 4th stage (N4), but this has been combined with N3 since N4 just presents with similar brain waves as N3 but more pronounced. These stages of sleep are classified based on the electrical activities of the brain in each period. They are measured in waves through an electroencephalogram (EEG).
Beta waves are high-frequency waves (14 – 40 Hz) seen when we are awake, alert, and active. Alpha waves are slow waves (7.5 – 14 Hz) and appear when we start to relax. Theta waves are slower (4 – 7.5 Hz) and are seen as we start to sleep. Delta waves are even slower (0.5 – 4 Hz) and are seen at the beginning of deep, dreamless sleep.
In Stage 1 (N1), we start to relax, feel drowsy, and enter the light sleep phase. This is the transition between wakefulness and sleep. We may experience sudden muscle contractions that give us the sensation of falling. Heart beat begins to decrease, breathing becomes more regular, and eye movements slow down. Alpha waves start to appear then gradually disappear to make way for Theta waves as we enter the actual sleep stage.
Stage 2 (N2) is the beginning of real sleep. Eye movements stop, and we become less responsive to external stimuli. Rapid bursts of brain waves (sleep spindles) are seen but the brain waves are really slow in general and dominated by Theta waves.
Stage 3 begins with N3, the start of deep sleep. Low-frequency, high-voltage waves (Delta) appear between high-frequency, low-voltage waves. This brain wave pattern progresses to N4 with more Delta waves. It’s the stage of the deepest sleep. Our muscles become completely relaxed, breathing slows down, blood pressure drops, hormones are released, and cells regenerate. It’s the most restorative stage of sleep. We may dream, although it’s not common. But if we do, the dreams aren’t as vivid or as memorable as those in the REM stage.
REM sleep is the dreaming stage. It’s characterized by rapid eye movements (hence, the name). The dream-like state is due to the combination of Beta waves (wakefulness) and Alpha waves (sleep). We experience partial paralysis of our skeletal muscles at this stage as a way of protecting us from injuring ourselves by unconsciously acting out our dreams. Sometimes, this safety mechanism fails, and susceptible individuals experience night terrors, sleepwalking, sleep talking, and bedwetting.
Sleep and Hormones
The regulation of sleep is mainly hormonal. Melatonin is the hormone that signals us when it’s time to sleep. It’s produced in a tiny gland in the brain called the pineal gland. Its production and release are also bound by the Circadian Rhythm. It starts to elevate around 9PM, peaks at midnight, and goes back down to normal after 7AM.
While melatonin affects our sleep, sleep also affects the other hormones in our endocrine system, which controls our hormonal functions. Hormones that promote repair and development like the growth hormone are produced during sleep. At the same time, hormones that promote breakdown and energy production like cortisol and thyroid-stimulating hormone are suppressed.
Sleep also affects our insulin production. It’s the deficiency of insulin that causes diabetes. There are studies that show that people who sleep less than 5 hours or more than 9 hours compromise their insulin production and make themselves more prone to developing diabetes. If you’re diabetic or have risk factors for developing it, make sure to get quality sleep consistently.
Other hormones that are affected by sleep are leptin and ghrelin. Leptin suppresses appetite while ghrelin promotes it. In sleep deprivation, production of leptin is decreased and production of ghrelin is increased. The double whammy of the lack of suppression and increased stimulation of appetite leads to weight gain and obesity.
This becomes a vicious cycle. Lack of sleep can lead to obesity. Obesity is a risk factor for obstructive sleep apnea (OSA), OSA disrupts sleep, and the cycle goes on.
Lack of sleep also causes lack of energy and fatigue. This makes it difficult to exercise and further increases the risk for weight gain and obesity.
A few hours before we wake up, our blood pressure and heart rate increase. This increases the risk of having a heart attack in the early morning if you have a heart condition. Aside from the elevation of heart rate and blood pressure, the lack of sleep has also been associated with a higher risk for heart attacks. Studies suggest that having 5 to 9 hours of sleep at night can greatly reduce these risks.
The Immune System
The interplay of sleep and the immune system is bidirectional, i.e., they affect each other. When battling an infection, we’re stimulated to have a longer total sleep time, especially in the deep sleep stage. This is our bodies’ way of fighting off the infection and promoting healing. Conversely, pathogens try to cut our sleep time short through a complex process with our immune factors that are yet to be fully understood. This can delay healing. It’s also the reason why bed rest is very important when we’re sick.
Mood and Mental Health
Much like in the immune system and sleep, the relationship between mental health and sleep is also bidirectional. Lack of sleep causes mental health problems and mood swings. Mental health problems and mood swings in turn affect the length and quality of sleep. Insomnia is a common presenting symptom of substance abuse, eating disorders, anxiety disorders, and psychotic disorders.
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How to Have Quality Sleep
1. Set your body clock. Develop the habit of sleeping at the same time and waking up at the same time. This will train your body when to sleep and when to wake up, making it easier for you to have quality sleep.
2. Keep it dark. The soft glow of a night lamp may be soothing but light disrupts production of melatonin which in turn will disrupt our sleep.
3. Sounds off. Sounds, even soft music, can also disrupt melatonin production.
4. Shut down electronics. Mobile phones and electronic gadgets emit radio and electromagnetic frequencies that interfere with the normal frequencies of our sleeping brain waves. Turn them off or put them at least 2 meters away from your bed.
5. Avoid naps. If you have to, do not exceed 20 minutes and don’t do it less than 8 hours before your expected bedtime. If you need to be more alert in the afternoon, take a short walk, do some stretching, or drink cold water.
6. Avoid caffeine and alcohol especially after lunch. Even if alcohol makes us tipsy and lets us fall asleep easier, it prevents us from reaching the regenerative depth of sleep.
7. Eat light. Sleeping with a full stomach will make it hard for you to sleep well. Meals should be light and finished at least an hour before bedtime.
8. Stop smoking. Nicotine is a stimulant. Cigarettes make it hard for you to have quality sleep.
9. Keep it aligned. If you sleep on your side, prop enough pillows to keep your nose aligned with your spine.
10. Mind your workout. Exercise is a good way to help your body sleep better. However, the energy burst can last up to 4 hours so avoid strenuous physical activities close to your expected bedtime.
11. Hold the fluids. Drinking anything 2 hours before sleeping can wake you up at night for a trip to the bathroom, so consume your fluids early.
12. Beds are for people. If your pets sleep in your bed, their movements can wake you up. Provide separate beds for your pets and train them to sleep there.
13. Beds are for sleeping. Do not associate your bed with eating, reading, watching TV, or anything work-related.
If your sleep problems aren’t easily solved by these tips, they may have deeper causes. Visit us at Aegle Wellness Center or set an appointment via firstname.lastname@example.org or +632-737-0077 so we can assess your condition, and guide you on the interventions to resolve your sleep concerns.
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