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  • Writer's pictureRyan Allen

“Mother Nature’s best effort yet at immortality”

At the time that this blog post is published, I will be in the middle of taking my MCAT exam, for which I have been studying intensely for months now (in fact, writing this post is a welcome break from an around-the-clock schedule of studying). On top of some serious, large-scale content review, I’ve been preparing for test day in several different ways to ensure that I’m feeling as sharp as possible. This includes things like adjusting my typical eating window well ahead of time, which is mainly due to my own personal preference of eating breakfast before the exam and not concerns regarding cognitive impairment from fasting, which is for another blog post.

The main adjustment I’ve been sure to make, though, is with my sleep schedule. In the case that there’s still a seed of doubt in anyone’s mind over the significance of sleep when it comes to test performance, countless studies have found a clear association between consistent good sleep (not just the night prior to an exam) and better grades, general cognitive performance, etc. So, my preparation when it comes to sleep didn’t begin Wednesday night; it started over a couple weeks ago.

I understand that many still will not fully appreciate just how crucial sleep is for not only academic performance, but health in general. For me, in the past, I was constantly told that sleep was important and recognized that, but still never thought it was that big of a deal. “Try and get your 8 hours, but if you can’t, it’s really not the end of the world” was the thought process. We all know what that type of thinking leads to: you start to accept shorter and shorter sleep hours, you’re never truly mindful of consistently getting enough sleep, you maybe get in bed at a good time only to spend an hour laying there on your phone (a phenomenon known as sleep procrastination), etc. This was the cycle I found myself in for years, always thinking I understood the magnitude of sleep’s benefits.

However, it really wasn’t until I listened to UC Berkeley neuroscientist Matthew Walker discuss sleep that I had a true appreciation for this incredible biological feat. Walker, who is arguably the world’s expert in sleep science, emphasizes the sheer evolutionary significance of sleep, calling it “Mother Nature’s best effort yet at immortality.” As he puts it, we should just imagine how important sleep must be for us to evolve to spend an entire third of our lives doing absolutely nothing. Just laying there, vulnerable to predators, not searching for food, not focusing on any tasks, not being conscious or aware of our surroundings. Yet, in the eyes of natural selection, it was still so beneficial to have this trait that today, scientists believe that virtually all animals exhibit some form of sleeping behavior.

That’s because, as you probably guessed, we’re not just “doing nothing” for that third of our lives. In fact, among other things, our brain is getting a much-needed deep clean. What happens is that our glial cells, which surround neurons in the brain and have previously been thought to just play a protective/supportive role, actually shrink significantly to allow cerebrospinal fluid to come through and wash away the molecular debris that we accumulate while in our normal state of wakefulness. Such accumulation appears to be quite harmful, and even looks to have serious implications in the development of Alzheimer’s disease. While we will certainly explore more surrounding the molecular mechanisms of sleep in future blog posts, it is hopefully now clear that its importance on the whole cannot be overstated.

Figure 1: Beta-amyloid clearance via cerebrospinal fluid in the glymphatic pathway. Beta-amyloid buildup in the brain is strongly associated with Alzheimer's risk. Mice lacking AQP4 (a water channel on glial cells) demonstrate significantly impaired clearance, suggesting a major role of this pathway in preventing beta-amyloid accumulation. (Image: Iliff et al., 2012)

For Walker, there are 4 pillars of sleep: depth, duration, continuity, and regularity. For today, I will just briefly focus on the “regularity” aspect, and how I’ve adjusted it for my MCAT test day.

These days (or at least before my sleep adjustment period), I typically sleep from around 10:30 pm to 6:30 am, which can be referred to as my chronotype. One’s chronotype appears to have some genetic basis, which could be why I feel my optimal sleeping window would actually be shifted slightly earlier. An individual’s consistency with their chronotype is remarkably important, because it turns out that our brains thrive on this regularity. They adapt incredibly well to fit our daily routine and patterns of behavior, through what many know as our circadian rhythms. While often just thought of in terms of sleep and cortisol levels, this really refers to the brain’s general coordination of its activity and bodily regulation with the 24-hour day. To simplify for now, throwing yourself off of this schedule leaves your brain confused, and often doing the wrong thing.

Starting my day off on the wrong foot in any way cannot be acceptable on any day, let alone test day. I calculated that I need to wake up at 5 am that day (yes, it starts at 7 am), so to compensate, a couple weeks ago I began to shift my sleep window to 9 pm-5 am. Having been on this schedule for many days now, I am feeling good, energized, and ready to start my day when I wake up. Hopefully, the benefits of this adjustment will be apparent when I get my test score back in a month or so.


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