Oxidative stress impacts your sleep; but how?
Ahh, sweet, sweet sleep. It's one of those things in life so highly sought after, but so elusive for many. Why is it that even when we get the recommended 8 hours of sleep, we can still struggle to wake up and feel tired by midday?
Because it’s so important to daily life, it’s important to dive into some of the science behind why we rest our eyes at night. We’ll cover the physiological reasons we need sleep, and some ways you can feel more energized even if you can’t get quite as much sleep as you’d like.
What happens when we sleep on a biological level?
Many scientists have studied sleep for quite some time now, but surprisingly, there still is not a widely recognized, single theory that explains why we sleep.
What we do know is that sleep is associated with many different biological processes, from the muscles in your toes to the tiny neurons in your brain. On the surface, sleep is also associated with electrophysiological (electrical properties of biological cells and tissues) changes, which can be recorded on an electroencephalogram. So knowing that, we can infer that sleep is definitely related to our cellular health and in turn, our overall wellbeing.
In stage one of sleep, the electrical waves emitted by the brain begin to slow down and become more rhythmic and controlled. As we move into deeper stages of sleep, it seems that electrical activity begins to increase and decrease at varying intervals until we reach the deepest stage of sleep, known as REM.
REM stands for rapid eye movement, because during this stage, your eyes rapidly move around from side-to-side under your eyelids (kind of creepy to think about, isn’t it?). During REM sleep, the electrical waves emitted by the brain begin to resemble those emitted by a fully conscious, awake brain, which is interesting given we tend to do our dreaming during REM sleep. Some say the higher frequency electrical activity emitted during REM sleep is associated with dreaming and the “feeling” of acting out our dreams…almost as if the brain thinks we’re awake. Even more eerie is that parts of the brain actually send signals to our muscles that essentially paralyze the body in this stage; otherwise, it’s very likely we would act out our dreams and potentially get ourselves into some sticky sleep situations.
As for the biological function of sleep (especially REM sleep), many hypothesize that it facilitates the rejuvenation of other important bodily systems and regulates processes necessary for a functional lifestyle, such as emotion and motivation. In fact, it appears that complete sleep deprivation or selective deprivation of REM sleep can cause disturbances in the thermoregulatory and caloric control systems of the body, both of which can have a fatal impact as temperature regulation and energy processing are essential functions to any living organism.
In animals, it was shown that sleep deprivation causes them to lose weight despite eating plenty of food. It also causes them to seek out warmer climates despite the consistent temperature in their surrounding environment. In other words, temperatures that were previously comfortable appeared uncomfortable after these animals experienced sleep deprivation. It’s almost as if a loss of sleep can make the world around us feel colder—have you ever experienced this? It’s odd, but weirdly makes sense.
How does sleep make us feel rested?
First and foremost, the sleep process begins with increased activity of certain neurotransmitters that are responsible for relaxing the body and making us feel “sleepy.” For instance, the happy hormone called serotonin is converted to a hormone called melatonin (you may recognize this is as the widely marketed “sleep hormone”). Melatonin is responsible for the calming effect and preparing us for bed. It is typically produced as sunlight begins to dissipate and is sort of like a primer for sleep, in that it prepares the body for rest and signals the brain to slow down and seek out a comfortable place to relax.
Second, sleep is associated with a myriad of chemical processes that are thought to rejuvenate the body and replenish energy systems by reducing the amount of oxidative stress experienced throughout the day. As you’d expect, it acts as a bit of a reset for your systems and allows your body to do what it needs – such as fight off infection and as mentioned, reduce oxidative stress to prevent unwanted things like inflammation and brain fog.
In fact, one of the leading theories in sleep research is that the accumulation of oxidative particles like reactive oxygen species (ROS) causes sleepiness, in part due to their blockade on the body’s ability to process energy and reduce inflammation.
The link between oxidative stress and tiredness
Let’s remember that oxidative molecules such as ROS are generated from metabolic activity in the cell, and oxidative stress results when the cell begins producing more ROS than it can remove. The potential for oxidative stress to occur increases as a cell’s rate of metabolic activity increases, and this is particularly the case for all sorts of cells that are necessary for keeping us awake and moving around.
The thing is, simply being awake is a metabolically demanding process and requires high levels of neuronal and muscular activity. Critically thinking, making decisions, regulating emotion, and staying motivated are all cognitively, metabolically demanding activities that produce wear and tear on your body. Simply being alive in this world and staying awake for a majority of our day (depending on your lifestyle) requires a lot of energy and as such, is a key contributor to oxidative stress.
One of the prominent theories in sleep research is that sleep is a replenishing and rejuvenating phase of our 24-hour cycle, responsible for slowing down metabolic activity while we sleep, allowing us to feel refreshed the next day. After all, when we sleep, neuronal activity decreases, thereby reducing the production of ROS and the generation of oxidative stress.
As a complement to the oxidative stress hypothesis of sleep, it is thought that the accumulation of ROS throughout each waking day primes the brain for sleep once a threshold of ROS is reached – which in simple terms makes sense. The more strain on your body, the more tired you’ll be and the more recovery time you should allow.
In other words, let’s say the body’s limit of ROS in the cell is 75% (completely arbitrary, just an example); once the amount of ROS in the cells reaches or exceeds 75%, certain chemicals are released that signal the body and brain to begin winding down and to initiate processes that are necessary to bring that level down below the threshold. One of the best ways to do this, of course, is to get some shut eye.
This link between oxidative stress and sleep is further supported by pre-clinical studies where researchers specifically targeted a chemical called NADPH, which is important in the generation of energy within the electron transport chain. It appears that NADPH is a chemical signal that reflects the relative amount of oxidative stress a cell is experiencing. NADPH flips between two chemical compositions, and the difference in the way NADPH appears chemically is related to the signals it sends to the brain to sleep or stay awake. Knowing this, it’s obvious there’s a convincing link that's been established between oxidative stress and sleep.
As mentioned, lack of sleep can increase oxidative stress in the body, which can further promote sleepiness, brain fog, lethargy, etc. Unfortunately, if one continues to experience sleeplessness, this oxidative stress accumulation has the potential to shift the body’s ability to reduce inflammation that is caused by increased ROS. Over time, this can lead to chronic inflammation, or inflammaging, as the body’s anti-inflammatory response becomes compromised from its own insufficiency and/or overactivity of the pro-inflammatory systems. Because aging is related to chronic inflammation, this may be why aging is linked to oxidative stress and sleep quality changing as you age.
General overview of how you can improve your sleep quality
In general, the best ways to improve your sleep are to ensure that your body keeps oxidative stress in check. This can be done by getting regular exercise, including antioxidant and anti-inflammatory foods and supplements in your diet, and ensuring you practice good sleep hygiene. This can be as simple as limiting or eliminating water, alcohol, and caffeinated beverages a few hours before the time you normally go to bed. Reducing liquid intake before bed can limit the need to hit the restroom, which can either keep you up or wake you up in the middle of the night. If you’re sensitive to caffeine, you should be cutting this out of your afternoons as well, as the longer-term effects of this compound can complicate the brain’s ability to relax at night.
You may even want to include a white noise machine and a blackout mask, and ensure your sleeping quarters are nice and cool to optimize conditions for a restful sleep.
As for those who look to caffeine for that energy boost—don’t be fooled; it doesn’t actually provide extra energy. Instead, it simply blocks receptors in the brain that signal tiredness and sleepiness (i.e. adenosine receptors). And while this may block receptors for tiredness, making you feel awake, the brain continues to generate oxidative stress and ROS regardless of how many cups of coffee you’ve had. If you were to keep blocking these receptors by consuming caffeinated beverages throughout the day, you may feel even more tired once that extra cup of joe begins to wear off (aka “the crash”).
Overall, try to look for alternative sources that actually provide energy following that morning coffee like natural fruits, going for a brisk walk mid-morning and maybe swapping to a tea in the early afternoon before cutting off your caffeine intake for the day.
Never underestimate the power of habits in your day – as humans we crave excitement, but thrive in routine. Allowing your body to wind down and relax a few hours before bed can provide an even more restful sleep. We hope this helps you get those much desired ZZZs!