Circadian (4): REM or Non-REM?

I have been avoiding talking about REM sleep until today because the public (mis)understanding is that REM is the "real deal." People will come to me and show how much REM they had the night before the appointment, based on their smartwatch or Oura ring, but in the same breath complain of symptoms of a broken circadian rhythm. If I suspect this is the case, I usually have to spend time deconstructing the blind faith they put in these gadgets and then offer an alternative investigation to prove or negate the diagnosis. Moreover, it is impossible to tell apart the phases of NREM sleep using movement, heart rate, and respiration—which are the three main parameters these wearables depend on.

In my understanding of the human body, every stage of sleep is important. If we look at the sleep cycles, as we go deeper into the night, we spend longer in REM as opposed to NREM 3. You don’t want to spend a lot of time in REM in the early part of the night; that will throw everything out, too. See, quantity is not everything. Timing is. The timing of everything matters.

Now think about the late-night scrollers, film-watchers, gamers, and workaholics who don’t go to sleep until 3 A.M. They have missed the best of NREM 3. Although they might get their normal share of REM, they often come to me complaining of RSI and all sorts of slow-healing chronic injuries. As a matter of fact, my first experience encountering RSI was before graduating, when I had a friend at Cardiff University with this then-rare diagnosis. I remember clearly that he was an avid late-night gamer. Back in 2006, late-night gaming was relatively uncommon. Refer back to Circadian 2 if you don’t remember that growth hormone is made during NREM 3.

Without NREM 2, the glymphatics (Circadian 3) will always be on the timer to finish its job. NREM 2 provides a sustained duration for the "power wash" to continue to happen. At least half of our sleep will be in NREM 2. This is when we put memories away into precious slots and consolidate new motor skills. If you want to take on a new sport or hobby, you really want to focus on this bit of sleep. Even my Cardiff friend could have used this advice for his hobby.

NREM 1 is absolutely critical. A good NREM 1 is your best bet in your fight against insomnia. It is the bridge between awake and asleep. You know those sleep jerks we have once in a while? Well, that is because this "bridge" wobbles at times. The smoother your NREM 1 is, the better your transition between awake and sleep will be.

Are you ready for a shocker? Well, coffee—by blocking adenosine, which is what the body uses to sense how desperate it is for sleep—causes you to stay longer on this bridge. As a consequence, you won’t spend as much time as you ought to in NREM 2 or 3. If you think a cuppa in the morning is not going to affect you at night, you may want to read on.

A large cup of coffee typically has about 200mg of caffeine. It goes into the body and makes its way to the brain. Caffeine parks itself in some unique "parking spots" where adenosine normally belongs. Caffeine, however, is more forceful than adenosine, so if the two are present, the latter has to give in to the former.

Adenosine is our tiredness counter. Without adenosine, the body is unable to feel how much sleep it needs—this is called sleep pressure. Sleep pressure influences how much time we spend in each of the sleep stages. If your sleep pressure is low, then you spend too much time in NREM 1. If it is too much, then you spend no time there. We call this "passing out." So, really, you want it to be just "average."

Fortunately, the 200mg of caffeine you take in the morning will not all remain in those parking spots by night time. The body has ways to get rid of stuff so we are not eternally doomed by our mistakes from yesteryear. We typically process half of whatever caffeine amount we have every 6 hours. So by midnight, you might be left with 25–30mg of caffeine, reducing your sleep pressure. If you do the math, it takes about 30 hours before your body is free from your last dose of caffeine. Yes, your coffee from yesterday morning was still there when you had another cuppa this morning. You basically top it up every morning before its effects are completely gone.

If you have little sleep pressure, it is harder—although not impossible—for your body to maintain a longer REM cycle. You might be deceived into thinking that you have good REM from the dreams that you have. Here is the truth: dreams can happen at any sleep stage. The dreams are different in different stages, but most people today won’t be able to definitively tell if they were dreaming from a REM or NREM 1, 2, or 3 stage.

In the past, people were definitely more in tune with their bodies and sleep. Thomas Edison was known to frequently have his "light bulb" moments during NREM 1. Dmitri Mendeleev wrote down his periodic table after seeing it in NREM 2-dominant sleep. Winston Churchill used NREM 3 to do 1.5 days of work in one day during WWII. Albert Einstein famously claimed that the theory of Special Relativity came to him in a dream about cows being electrocuted. REM allows the brain to ignore the laws of physics, which was what Einstein needed to "see" time and space differently. Today, sleep is no longer an art for the modern human. I guess this is a sacrifice we have made for taking up wearable technology.