What Is Sleep For?

Every human, animal, insect, and even (we think) plant does something that looks like sleep. This is a pivotal function, but what is it for? It might surprise you to know that a lot of what we know about sleep is still theoretical.

Everyone knows that the quality and quantity of sleep deeply affect how you feel, how much energy you have, how much emotional tolerance (or how little) you have, and even your metabolic state. Research is showing that REM sleep is most critical for brain performance and memory formation, but the combination of REM and deep sleep helps you feel rested.

What is Sleep For, and Eight Keys to A Healthy Sleep Cycle

Why Do You Sleep?

Both the research we have and our intuitive sense of ourselves say the same thing. Sleep is when we heal, repair damage, tidy the house of our physical body, and when our brain has the time to sort and process the events and interactions of the day. Sleep is when a lot of our own physical maintenance happens, including repair, regeneration, and detoxification.

Phases of Sleep

During sleep, you cycle through the two major phases of sleep: rapid eye movement, or REM, and non-REM sleep. Each cycle takes between 80 and 100 minutes, and most people experience four to six sleep cycles per night. Many people wake more easily between these sleep cycles.

REM Sleep

The rapid eye movement phase of sleep is named after its most characteristic feature, which is that your eyes move rapidly behind your eyelids. During this sleep phase, your brain shows similar levels of activity to those you experience during your waking hours. Dreaming usually happens during REM, although it can happen in other sleep stages too. In normal sleep, your muscles become limp to protect you from acting out your dreams. REM sleep levels are usually higher in later parts of the night and lower in cold temperatures because during REM, your body temperature is poorly regulated. Newborns spend more time in REM sleep than adults, and the amount may decline with age.

REM sleep is associated with memory consolidation, helping your body keep what is useful and discard what isn't necessary. This includes new learning and motor skills. REM sleep is also believed to play a role in emotional processing and brain development. Your amygdala, the area of your brain most involved with emotions, is activated in REM sleep.

Stage I - Light Sleep

This is the first, drifty phase of sleep in which your brain and breathing both slow down, and your body becomes more relaxed but retains some muscle tone. The brain waves you see in this sleep phase are called low-amplitude mixed-frequency waves, and they take over from the alpha waves that predominated during the drowsy period.

Stage II - Light Sleep

This stage is also characterized by light sleep, but it is becoming deeper as both heart rate and body temperature decrease. This phase is akin to a transition to deeper sleep, and brain activity is characterized by specific brain wave patterns, including sleep spindles and K-complexes.

Stage III - Deep Sleep

This phase is characterized by deep, slow brain waves called delta waves. Waking from this sleep phase is extremely difficult and feels like dragging oneself out of deep water, a phenomenon known as sleep inertia. In deep sleep, your body works on physical repairs, including bone, muscle, connective tissue, and immune system activities.

MTHFR, Methylation, and Sleep

Research on the associations between MTHFR and sleep has yet to be done. Not a single study has been published, yet sleep difficulties are among the top self-reported symptoms associated with MTHFR. One interesting case report was published in the Journal of Clinical Sleep Medicine following a patient with chronic insomnia who was resistant to both conventional medications for sleep and cognitive behavioral therapy for insomnia. Routine lab work revealed high homocysteine levels, prompting the physician to order genetic testing. No surprise, a homozygous C677T mutation was found. In this case, targeting the MTHFR polymorphism with methylcobalamin and folate resolved the sleep issue, which is promising for MTHFR mutants.

Sleep and Circadian Rhythms

Circadian rhythms are 24-hour cycles that operate continuously in the background to help your body perform functions and processes at their optimal time of day. The sleep-wake cycle is one of the most essential circadian rhythms. Like many others, it is determined by a biological clock within your brain that is directly influenced by environmental cues, especially light. Other factors in your environment can also affect your circadian rhythm, including exercise, social activity, and temperature; however, light has the strongest influence on basic physiological timing.

The darkness of the setting sun is the primary signal to your biological clock to begin production of melatonin, your primary sleep hormone. Remember that if you spend your evening staring into the mini-sun of a computer or TV screen, this action is stunted. Even with blue-light blocking glasses or screen protectors, the amount of regular light through the rest of the spectrum is enough to harm this process. Also, the rays of the rising sun help to trigger cortisol release and boost neurotransmitters that get you up and moving for the day.

Circadian rhythms promote consistent and restorative sleep when properly aligned to your environment. When misaligned, your circadian rhythm can promote insomnia and sleep dysfunction. One of the easiest ways to tell if your circadian rhythm is aligned properly is if you notice that you begin to feel sleepy when the sun is setting.

Eight Tips for A Healthier Sleep-Wake Cycle

Maintaining a healthy sleep-wake cycle comes down to setting a normal routine for yourself through the day that optimizes your activity with your biological clock.

1. Maintain a regular sleep schedule. Try to wake up and fall asleep at roughly the same time every day.

2. Sun-worship. Get exposure to sun as early in the day as you can. If that is too difficult, consider investing in a full-spectrum therapy 10,000 lux therapy lamp to use for 15 minutes at the start of every day. This type of light has been shown to increase sleep quality and improve depression.

3. Physical activity. Exercising or being physically active every day constantly improves sleep quality and helps maintain a healthy sleep-wake cycle.

4. Avoid caffeine after noon. Caffeine after noon has been shown to disrupt the sleep cycle for most genotypes. The exception is CYP 1A2 fast caffeine metabolizers, who can handle higher levels of caffeine, possibly later in the day (studies tentatively say before 3-4:00 pm.)

5. Low lights before bedtime. Completely outside of romantic potential for this habit, low lights and no screens for the two hours before your bedtime help to ensure a healthy sleep-wake cycle and go a long way to counteract the constant staring into a computer or TV screen that most of us engage in. Why not try candlelight and soft lamps for the last two hours?

6. Short, early naps. Napping has been shown time and time again to be amazing for your health and mental performance, but in terms of your sleep-wake cycle, the best naps are early afternoon and shorter than 90 minutes.

7. Make a sleep Zone. Your bedroom is your sleep zone, and making sure you have a comfortable mattress, appropriate bedding, and a calm, peaceful environment will help you maximize sleep time.

8. Consistent low-carb dinner. Dinner should be a light, balanced meal, eaten at least an hour or two before bed. When looking down at your plate, divide it into healthy quarters. 1/4 of the plate should be a protein like meat, eggs, fish, beans, or quinoa. 1/2 of the plate should be vegetables, not including starchy vegetables like corn or potatoes, and the remaining 1/4 can be carbohydrates like rice, corn, potatoes, bread, or other grains. If you want something sweet, make sure it is small and eaten right after dinner (not the giant impulse bowl of ice cream right before bed). Maintaining a healthy blood sugar overnight will help to keep your body in deeper sleep.

While we don't know exactly what sleep is for, we do know it is pivotal for health and wellbeing, and that improving your sleep will likely improve your quality of life. Sleep is something worth nurturing and protecting for your health now and in the years to come.