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  • Writer's pictureRyan Allen

Preserving sleep “pressure” and things to avoid

In my post introducing the science of sleep just over a month ago, I emphasized the importance of good sleep, insisting that it is a critical yet largely neglected aspect of preserving our health. However, I did not mention all too much about the actual practice of getting good sleep, which is not so simple. This is something that many of us seem to have different experiences with, but there are still many common strategies we can all engage in to ensure we are getting the best sleep we can. For now I’m going to focus primarily on things that can disrupt our sleep, because while we can definitely do many things to improve our sleep, it’s more often a case of avoiding what’s harmful. In other words, I think for most people there is far more net benefit available from removing these harmful habits than there may be from efforts to actively enhance sleep.

To start, it’s first helpful to briefly think of the science behind why we get tired or “sleepy.” What actually is sleepiness? It seems that this feeling is explained biochemically by the buildup of a molecule called adenosine. Some may recognize this compound as a building block for adenosine triphosphate, or ATP, which can be thought of as our cells’ “energy currency.” During the day, as we’re awake and active for 16 hours, our bodies accumulate all this adenosine. This increases our “sleepiness” until eventually the adenosine is cleared away during our sleep. In that sense, the buildup of adenosine can be likened to a sleep “pressure” of sorts. The more we accumulate, the greater our drive to sleep. So, an integral part of preparing yourself for a good night’s sleep is building up adenosine and maintaining this sleep pressure.

As it turns out, there are numerous things that can disrupt this sleep pressure. You may have guessed one of them: naps. Napping is actually a complex topic when it comes to proper sleep hygiene, as there are many different beliefs around appropriate timing, duration, etc. While I will outline the finer details of this in the future, for now it suffices to say that long naps (2+ hours or so) on the whole are probably disruptive. When you nap, you’re of course sleeping, and with that you’re removing some of that adenosine sleep pressure you’ve been building up so far during the day. The longer you nap, the more of that pressure you’ll lose. Then, when your normal bedtime comes around, you’re going to have much less of that pressure accumulated than you otherwise would, and it can be a lot tougher to fall asleep and stay asleep. So, especially if you have trouble with these things, try to keep naps on the shorter side.

Another thing that combats sleep pressure is caffeine. Caffeine is a known adenosine receptor antagonist, which basically just means that it blocks our neurons’ receptors for adenosine. If adenosine can’t bind the receptors, its pathway of action cannot be activated, and our bodies won’t feel the effects of this sleep pressure. This is a main mechanism of caffeine in keeping us wide awake, but it’s then of course harmful when we’re trying to sleep.

Now, many studies across several different fields have actually associated caffeine with lower risk for various diseases, so this is not to be entirely anti-caffeine. What matters more is the timing of caffeine consumption. The half-life of caffeine in our body (the time it takes for half of the caffeine to decay) is 6 hours. As sleep science authority Matthew Walker describes, this means that consuming a cup of coffee at noon would leave a quarter of that caffeine still in your system at midnight when you’re trying to sleep. Imagine the effect of drinking a quarter of a cup of coffee right before bed. It’s best, then, to consume caffeine in low-to-moderate doses and as early as possible in the morning after you wake up.

Also in the category of things to avoid are sedatives. Often mistakenly viewed as sleep aids, things like sleeping pills and alcohol are effective at helping someone lose consciousness, but not at actually helping them get good sleep. As Walker puts it, the unique electrical brainwave “signature” of your sleep is not conserved. In short, the quality of our sleep is dependent on this signature, on the contributions and alternating patterns of different brainwaves. Knocking someone out with a frying pan might also be effective at getting them unconscious, but probably not at helping them get this healthy, quality construction of sleep.

When it comes to alcohol specifically, it is even worse than other sedatives because it has the additional effect of fragmenting sleep. Drinking alcohol causes you to wake up several times during the night, but for such brief periods that you often don’t recall doing so. In addition, alcohol is a potent diuretic, meaning that you have to get up much more during the night to urinate. Therefore, do whatever you can to generally avoid alcohol, at least in large quantities. Try for one or (at most) two drinks in a given night.

Lastly, there has been lots of research to suggest that blue light devices negatively impact your release of the hormone melatonin, which is basically the “sleepiness hormone.” However, Walker is less convinced that blue light is the culprit from these devices. Rather, he believes that they negatively affect sleep by generally “activating” or physiologically arousing our brains, making us stay awake and alert despite the sleepiness we may have. While the exact harmful mechanism of action of these devices is yet to be determined, the recommendation remains to avoid such devices for about an hour or so before bed. Really, just any period of time to stay away from them and wind down at all before going to sleep would be a good start.

We are almost all victims of a combination of these things when it comes to our sleep, but the more we learn to manage, control, and sometimes just avoid them, the more we allow ourselves to get the quality sleep that we crave. If you struggle with multiple things I’ve listed, try to focus on resolving just one to start. I’m sure you’ll find that adjusting it may not be as hard as you previously thought, and it will undoubtedly have a positive effect on your sleep health.


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