Early at 8 a.m. after studying all night and after a couple more classes, you get to your comfy bed, and your mind can only focus on one thing– a perfect midday nap. Naps have become a staple for me this quarter, but it has thrown my sleep schedule off. You know, when you stay up well past midnight once, and then, it ends up being a part of your daily routine. I can’t help but wonder if my fragmented sleep schedule is why I can hardly focus in class or why my social battery is so low.
So how come naps are so enjoyable if it can throw off your sleep schedule? Or wait… does it even affect your sleep schedule? Well, to find out, it is important to understand the circadian rhythm, also known as the body’s “internal clock,” and how it affects the sleep-wake cycle. The sleep-wake cycle majorly affects human productivity, and with an improper sleep schedule, it makes it difficult to carry out your daily life.
It begins with the biological rhythms
Circadian rhythms are often referred to as a biological clock, but what does that really mean? Rhythms refer to the physical, mental, and behavioral cycles that occur within 24-hour periods. This is important in allowing the body to carry out its daily functions at appropriate times such as hormone release or maintaining body temperature. For example, body temperature drops at night, signaling the body that it needs to rest. The body aligns its rhythms with day and night with the help of light, which is processed in the hypothalamus. The hypothalamus is located in a deep region within the brain, and I could go into depth on all of its functions, but that would be its own separate blog. Most importantly, the function we are going to focus on is how it manages sleep with help from the suprachiasmatic nucleus (SCN). The SCN is a bilateral structure inside the hypothalamus composed of about 20,000 nerve cells that receive synaptic input from the eyes. A bilateral structure is symmetrical, and this is important for the SCN so it can properly function in both hemispheres of the brain to efficiently operate circadian rhythms. With direct input from the eyes, light is processed, and signals can be sent to the body to infer that it is daytime, allowing the SCN to specialize in managing the human body’s internal clock.
To better understand how light processing maintains circadian rhythms, let’s use jet lag as a quick example. For most people, flying across the world results in a couple of days of jet lag, where your body has yet to adapt to a new time zone, so your sleep-wake cycle is still aligned from wherever you originally took off from. This is because the body is adapted to using light as the primary signal to awaken and begin performing its daily routine and functions. So, when you are in a new time zone and day and night are switched, it takes time for the body to adjust to the difference in light, having to change the circadian rhythm timing.
Stages of sleep and GABA
Circadian rhythm is all about cyclic oscillations, especially with the stages of sleep. While there are multiple stages of sleep, there are two main categories: rapid eye movement (REM) sleep and non-REM sleep. The stages of sleep are regulated with the help of GABA, and it is vital to understand what it is and how it works before we dive into the different stages of sleep.
GABA is an inhibitory neurotransmitter that regulates circadian rhythm, especially with sleep and stress. GABA binds to its receptors and inhibits other neurotransmitters from responding to small stimuli. Since GABA hyperpolarizes the neurotransmitters that would respond to these stimuli, it increases the threshold needed to fire an action potential. Depolarization is what allows the firing of action potential, so when cells are hyperpolarized, positive ions flow out of the cell membrane so that it can not reach the threshold. This can be used to interpret why GABA is so important for sleep and stress regulation. Think of it to ease the mind from constantly firing responses to small stimuli, reducing anxiety, and allowing the body to respond to signals that it is time to sleep. Insufficient amounts of GABA may lead to sleep disorders, the most common one being insomnia. An 8-week study was conducted to monitor the relationship between GABA and sleep, where individuals who were unable to get proper sleep were treated by consuming capsules that contained GABA. The results of this study confirmed that GABA does have a strong influence on circadian rhythms as participants noted that their sleep schedules did improve, where they experienced longer, preferred amounts of non-REM sleep.
Beginning a sleep episode of multiple cycles, first you go through stages one to three of non-REM sleep. Non-REM sleep accounts for around ¾ of time asleep and involves the relation between the brainstem with the thalamus and cortex. During non-REM sleep, GABA hyperpolarizes the neurons in the thalamus and cortex. Each stage of non-REM sleep varies in time, where they progressively get longer. To start, stage 1 of non-REM sleep is the shortest, lasting just a few minutes and can easily be disrupted. Stage 2 of nonREM sleep gets longer as the cycle repeats and accounts for around half of total sleep. Stage 2 is where you enter a progressively deeper sleep, until stage 3 which is the deepest stage. Stage 3 is where you are in a deep sleep called slow-wave sleep (SWS), lasting anywhere from 20 to 40 minutes.
Next is REM sleep, which lasts only a couple minutes the first cycle but progressively gets longer as the cycle repeats. This is the stage of sleep where you visualize most of those bizarre imagery and scenarios that you can hardly recall in the morning, aka dreams. REM sleep is by far the most interesting stage, as dreaming causes rapid eye movement and brain activity that is like when awake. On average, REM sleep repeats 4-5 completed cycles each sleep episode.
Prolonged effects: Insomnia
Maintaining circadian rhythms with the sleep-wake cycle is vital to carry out daily functions. Improper sleep causes complications in productivity, which can be called worker fatigue. This fatigue refers to the mental state between being awake and asleep. Worker fatigue differs from simply being tired, where prolonged inadequate sleep and disruption in the circadian clock creates more drastic effects in individuals. This fatigue involves the mind not being able to carry out daily functions including reaction time and problem-solving abilities. This may also result in problems with the immune system and can lead to long-term health issues.
Insomnia is the most common sleep disorder where an individual struggles with falling asleep or staying asleep. In 2011, a study was conducted to see how prevalent insomnia is in the U.S. while demonstrating its significant impact on productivity levels. The results concluded that an estimate of 23.2% of the population experienced insomnia, contributing to decreased work performance which results in $63 billion lost annually. This study illustrates how insomnia impacts the economy but can also be used to demonstrate how it commonly affects people. As previously mentioned in terms of productivity, individuals with insomnia are unable to perform daily tasks and instead struggle throughout the day with fatigue.
So, yes or no to naps?
Understanding your circadian rhythm is crucial as it maintains your internal clock. Aligning your day-to-today life with circadian rhythms boosts your health, productivity, and overall well-being. Where the body specializes in being able to function on its own, it is still our responsibility to align our activities with our rhythms to maintain a healthy lifestyle. At the beginning of this blog, we asked if naps are harmful to circadian rhythm. I do not believe that there is a clear answer after learning about the intricacies of sleep; longer naps can lead to disordered circadian rhythms as waking up in a deep stage of sleep can cause an abrupt change in brain activity from slow to active. However, shorter naps do not tend to reach the state of deep sleep and brain activity during a catnap can still resemble itself when awake. In addition, sleeping during the day may cause disturbances to light-to-signal processing. However, after taking a closer look at an example of a common sleep disorder, these imbalanced patterns are caused by prolonged disturbances. My opinion? A nap everyday may not be ideal, but a once-in-a-while post-class nap never hurts anyone.