This post is inspired by Aric Prather, a sleep scientist at UCSF, who partnered with wired.com to explain sleep in five levels of difficulty. Watch the video here. 

Prather’s bio from ucsfhealth.org:

Aric Prather is a psychologist who treats insomnia with individual cognitive behavioral therapy. He also provides behavioral therapy to help patients adjust to using their continuous positive airway pressure (CPAP) equipment. Prather’s research focuses on how poor sleep impacts physical health and emotional well-being. He measures sleep habits to determine which study participants are vulnerable to sleep-related health problems and which are resilient, with the goal of developing new treatments. Prather earned his doctoral degree in clinical and biological health psychology from the University of Pittsburgh. Prather is a member of the Sleep Research Society, American Psychological Association, American Psychosomatic Society and Society for Affective Science.

Level 1 | All Species Sleep

Like an electric car plugged in overnight, our bodies and minds need to be regularly reset and recharged. The mechanism to do this is sleep. The process of sleep helps us recover from the previous day. Not only that, sleep helps us learn better, strengthens our immune system, and impacts our metabolism. Sleep keeps our body and mind healthy. As a matter of fact, sleep is so powerful that we have evolved to sleep for around one-third of our lives. That’s right, we sleep for around 20-30 years of our lives!

All living species sleep in some form or another. In the video, Prather talks about giraffes, who are very efficient sleepers. They slump over into a ball and sleep for only 30 minutes to avoid being hunted by prey. Hippos sleep underwater to keep their bodies cool. They float up to the surface to take a breath without waking up. Dolphins also sleep underwater, but their left and right parts of their brain alternate sleeping to keep alert, go up for breath, which allows them to survive. All living species sleep.

Level 2 | Two Types of Sleep

Sleep is a biological process that happens in our brains. Sleep is made up of different parts. The first part is non-rapid eye movement sleep (NREM). There are three stages of NREM sleep. They are boringly named N-1, N-2, and N-3. N-1 is light sleep, think of it as the point when you are drifting in and out of sleep. N-2 is still a form of light sleep where we spend around half of our time sleeping. N-3 is the really restorative NREM sleep. It’s where our brain waves are big a slow. We spend about 20% of our time in N-3 sleep.

The second part of sleep is rapid eye movement sleep (REM). You are probably already aware of this type of sleep. REM sleep is where dreams happen. We dip in and out of REM sleep during the second half of the night. Dip in and out? Yes, sleep happens in cycles. We actually wake up a lot during the night, but we just don’t remember it. Our bodies cycle through light sleep (N1, N2) and deep restorative sleep (N3, REM). The reason you sometimes feel terrible after a mid-afternoon nap? Well it’s because you were jolted out of your deep sleep part of the cycle.

Level 3 | The Drivers of Sleep

People between the ages of 18-65 need between 7-9 hours of sleep each night to maintain good health. Generally, the younger you are, the more sleep you need. Your health risk significantly increases when you get less than 5-hours of sleep.

There are two key processes that drive sleep in your body; process S and process C. Again, what’s with the boring names? Process S relates to the amount of time you are awake. Its basic principle is, the longer you are awake the sleepier you get. Prather relates this to a balloon analogy. When you wake up your balloon is flat. All of the sleepiness has left the balloon. As your day progresses more sleepiness fills up the balloon. As nighttime approaches, your balloon is full of sleepiness and the only way to let the air out of the balloon is to fall asleep. Prather mentions that napping sometimes lets too much air out of the balloon, making it harder to fall asleep at night. You want your balloon to fill up with sleepiness!

Process C is the sleeping master clock. It helps regulate your sleep schedule, also known as your circadian rhythm. It actually helps regulate all of our body’s biological rhythms. Process C times the release of melatonin from the pineal gland. It knows when to do this by picking up queues from your environment. When it’s dark and the sun goes down, it recognizes that it’s time to get ready for sleep, and instructs your body to start releasing melatonin. Therefore, it is helpful to have a consistent and regular bedtime routine. It reminds process C to start the sleep promoting melatonin release.

Level 4 | The Duelling Wake-Sleep System

Our brain is where sleep turns on and off. Prather calls it the “flip flop switch”. The flip flop switch transitions us between consciousness and unconsciousness. Or put another way, you are flip-flopping between an arousal system and a sleep-promoting system. The systems are mutually exclusive and you can only have one system going at a time.

When the arousal system (officially known as the ascending reticular activating system) gets activated, it wakes up the nervous system and endocrine system which leads to increased heart rate and blood pressure, and turns on your senses so that you are alert, mobile, and responsive.

These systems get operating instructions from the release of neurotransmitters. Dopamine and serotonin are both chemical messengers that regulate many of the bodily functions used by the arousal system. When you drink a Redbull, you are pushing the flip flop switch in a much stronger direction towards the arousal system. Activating more neurotransmitters.

When the flip flop switch is pushed in the direction towards the sleep-promoting system part of our brain, Process S and Process C start to take over and start releasing melatonin which prevents the arousal system from promoting wakefulness. This results in sleep.

Level 5 | Sleep and Brain Disease

Our bodies are amazingly complex machines. It’s made up of billions of particles, each organized and working together for the benefit our keeping our bodies healthy. Our sleep rhythms are an essential part of this system. What happens when they are disrupted?

There is growing evidence that people with sleep disorders and sleep disturbances have a higher risk of neurodegenerative diseases including both Alzheimer’s and Parkinson’s disease. We are just starting to understand how sleep impacts the detection and prevention of these types of diseases. One theory is that sleep acts like a dishwasher for the brain, eliminating some of the ‘bad stuff’ that promotes different types of brain disease.

Prather says “We’re still uncovering new things every day about how sleep works, but despite that, all of us know that sleep is fundamental to our health, and so I’m excited for sleep to kind of raise its profile among other health behaviors and get the investment and care that it needs.”