Sleep isn’t just laying still through the night. Rather, sleep is when your body performs many vital functions as it cycles through different stages, including rapid eye movement (REM), and non-REM N1, N2 and N3 stages.
N1 and N2 are lighter transitional stages between wakefulness and sleep. N3 (Slow Wave Sleep) is the deepest and most restorative sleep where your heartbeat, breathing, and brain waves are at their slowest.
Caption: Ideal sleep cycle, where N3 (Non-REM 3) is the deepest sleep and R (REM) is the most active type of sleep.2
REM sleep is paradoxically rather active when your body lacks movement while your brain frequency, breathing, heart rate and blood pressure increases. REM sleep is important for memory formation and emotional processing.3
According to the National Sleep Foundation,4 a good night of sleep means that:
- You fall asleep easily, within 15 – 30 minutes
- Your sleep is uninterrupted, with few or no awakenings throughout the night
- You achieve all sleep stages and cycle through them naturally
- You achieve sufficient lengths of deep (16 – 20%) and REM (21 – 30%) sleep of total sleep time of 7 – 9 hours
Most people know their sleep duration but are unaware of their sleep quality, which is best measured with a sleep study. Many consumer devices, such as the Oura ring and Resmed S+, can estimate sleep stages based on heart rates, breathing patterns and movements. In addition, energy levels, alertness, mood, cognitive function, and low resting heart rate are good indicators of sleep quality.
Deep sleep is when growth hormone, the anti-aging and growth-stimulating hormone, is released the most.5 Your nervous system shifts from fight or flight to rest and digest, so deep sleep helps your nervous system reset from daily stress. Insufficient deep sleep keeps the body stressed, which can increase blood pressure and the risk of stress-related illnesses.7
Deep sleep is when your brain cells get the cleanup they need because the glymphatic system, the brain’s housekeeper, is most active during deep sleep.8
- Increased inflammation and impaired immune function
Sleep loss increases chronic inflammation, which can worsen pain, allergies and autoimmunity.9 At the same time, sleep deprivation impairs immune function, making you more likely to catch infections and take longer to heal wounds.
- Increased hunger, cravings and insulin resistance
Sleep deprivation increases the hunger hormone, ghrelin and causes resistance to the satiety hormone, leptin.12-14 Sleep deprivation also causes insulin resistance, which may contribute to type II diabetes.15 Therefore, many people have worse cravings and gain weight during periods of sleep deprivation. Poor sleep drives obesity and makes it more difficult to eat healthy, control portions and get in shape.16,17
- Increased risk of cardiovascular diseases
Lack of sleep and sleep disorders are major drivers of cardiovascular diseases due to increased chronic inflammation, stress, insulin resistance, blood pressure and weight gain.18
- Hormone imbalances and infertility
Poor sleep increases the stress hormone, cortisol and thyroid-stimulating hormone.19 In healthy young men, one week of sleeping five hours a night reduced their testosterone levels by 10 – 15%.20 Since testosterone naturally declines by 1 – 2% every year, this reduction is equivalent to 10 – 15 years of aging.
In premenopausal women, short sleep duration is associated with irregular cycles.21 Women who suffer from polycystic ovarian syndrome are more likely to suffer from sleep disturbances and sleep disorders.22 Overall, sleep problems can throw off hormones and stress out the body, contributing to hormone imbalances and infertility.
- Accelerated aging
Lack of sleep promotes aging by throwing off metabolism and hormone balance, stressing out the body and increasing oxidative stress. People who sleep less have premature shortening of telomeres, suggesting that they age prematurely.23
- Poor exercise recovery
Because sleep deprivation keeps the body stressed and impair immune function, it reduces exercise recovery in all aspects, including diminished muscle strength, muscle growth, and exercise performance in response to training.24-26 Muscles also get repaired during sleep, specifically during stage 3 of your 5 – 6 stage sleep cycle. It’s in this stage that eye and muscle movement stops and the body starts releasing growth hormone to build and repair muscle tissue. But muscle recovery also begins before you even get to sleep. A great muscle recovery program should also include ample time in an infrared sauna, as infrared saunas enhance muscle recovery process by increasing blood circulation, carrying oxygen-rich blood to muscles that have been torn due to exercising.
- Worsened mental health
Sleep is a neurological process driven by the brain and for the brain. One night of sleep deprivation can worsen mood and emotional response. Poor sleep may increase the risk of developing mental health disorders. Also, disordered sleep patterns are common symptoms of psychiatric and neurological disorders.27 Severe sleep deprivation can lead to hallucinations and psychosis in healthy people.28
One single night without sleep can make the amygdala (the stress and fear memory center in the brain) significantly more reactive,29 which may increase anxiety and inappropriate responses to stress.
Although coffee may take away the fatigue and make you feel awake, it does not adequately replace sleep because it doesn’t provide the same restoration that your body needs. In addition, caffeine may not restore all deficits in brain function.35
Sleep disorders, such as sleep apnea and restless leg syndrome, also increase the same health risks as sleep deprivation itself. In addition, breathing disruptions during apnea episodes may also cause death and other health problems due to lack of oxygen to the brain.36 Unfortunately, 80% of cases of moderate and severe obstructive sleep apnea remain undiagnosed.37
If you are often tired or struggle with any of the health issues above, consider optimizing sleep and speaking with your doctor about ruling out sleep disorders.
Optimizing sleep quality involves supporting your natural circadian rhythm (body clock) and making sure your sleep pressure is high when it’s bedtime.
Your circadian rhythm helps you sleep at nighttime. The most potent circadian rhythm cue is light exposure, followed by body temperature, mealtimes and other activities.38 Excessive bright artificial light at night can lower sleep quality by increasing your nighttime alertness and reducing melatonin.39 In addition, staying up late and sleeping in can throw off your body clock and make it harder to sleep well in subsequent nights.40
To promote a healthy circadian rhythm, it is important to be exposed to bright light during the day and reduce blue light at night. Apps like F.lux and blue light blocking glasses can help reduce blue light exposure at night. In addition, it is important to stick to a bedtime routine that involves not eating too late, winding down, and going to bed at the same time every night. Last but not least, ensure that your sleep environment is cool and completely dark.
Many sleep remedies support sleep by promoting relaxation, helping you wind down towards bedtime, such as an infrared sauna session, lavender, passionflower, cannabidiol (CBD) and GABA supplements.41-44
Your sleep pressure is governed by levels of adenosine, inflammation and oxidative stress.45,46 High sleep pressure makes you sleepy and also deepens your sleep. Conversely, sleep reduces the levels of these molecules and makes you more alert. Caffeine makes us more alert by blocking adenosine receptors, but it may worsen sleep.35 As such, taking anti-inflammatory or antioxidants at night may reduce sleep quality.
Physical activity and heat exposure during the day can both promote a healthy circadian rhythm and increase sleep drive. The drop in body temperature afterward reinforces the circadian pattern and promotes relaxation.47 Sauna use, especially infrared sauna, can also elicit similar benefits while relaxing instead of working out. In addition, far infrared therapy may further improve sleep quality by increasing deep sleep in ways that do not involve heat.48,49
Relaxing in gentle heat, like in Sunlighten saunas, can be part of a great bedtime routine that improves sleep quality by promoting relaxation, healthy circadian rhythm and sleep drive.
Learn more about the health benefits of Sunlighten infrared therapy.