The circadian rhythm is a natural, internal clock that all living things possess. This cycle regulates our sleeping and waking patterns. One of the biggest contributions to our circadian clock are the natural light and dark cycles during a 24 hour period. Since we are a diurnal species, we are generally active during the daylight hours and asleep during the night. In humans, the circadian clock is as ingrained in us as our hair or eye color. We are all unique when it comes to what is the best wake up and sleep times, so each individual’s clock determines when they want to be awake, and this speaks to how some people are considered “early birds,’ while others are considered “night owls.” If you try to push against your natural clock and rhythm, you may encounter great difficulty as it is not natural for your body to shift its desire to be awake and asleep at alternating times. Take shift work, for example, when we are forcing the body to be awake throughout the night due to job requirements. It is simply unnatural and this inconsistent pattern can lead to health complications down the line. There are ways to push up your clock, but it takes a bit more work than simply adjusting your alarm clock.
The primary navigator for the circadian clock is daylight. When light enters the eyes and stimulates the suprachiasmatic nucleus (SCN), it stimulates our body’s awake centers in the brain and turns off the sleep centers. Conversely, the SCN also lifts the brake off of the pineal gland at night when it senses the lack of light. This allows our body to naturally release melatonin, the hormone that induces sleep. When it comes to proper sleep hygiene, it is very important to be mindful of your daily schedule. The circadian clock is hardwired into us, so if you continually move your sleep and wake schedule around, you will miss out on the beautiful, restorative sleep stages, particularly deep sleep, that occur in the earlier parts of the night. To explain, let’s say your body’s sleep window is from 11pm to 7am. Your body understands that from 11pm to 3am it will be rich in stage 3deep sleep, and from 3am to 7am, it will have more REM sleep. When you shift that sleep window and fall asleep at 2am instead of 11pm, your body has missed virtually the entire window of deep, restorative sleep. The same stands true if you decide to fall asleep at 11pm but choose to wake up at 4am instead of 7am. You’ve now missed out on the beauty of memory inducing REM sleep. Now you are off balance and your body begins to experience a jet lag effect, called social jet lag.
Normally a healthy person can adjust within one hour of their natural and normal circadian rhythm without noticing any major issues. But those larger shifts in sleep and wake cycles can significantly impact sleep quality and quantity. Social jet lag describes a pattern of sleep/wake characterized by a delayed schedule that normally occurs on weekends. In other words, staying up later and sleeping in later on the weekends when compared to the weekdays. Why is this an issue? Well. as mentioned above, it results in circadian misalignment. That means the body’s circadian rhythm is not aligned with your normal sleep/wake cycle. Now, come Sunday night when you need to get your rest for Monday morning, you will have difficulty falling asleep. For the whole weekend you’ve sent the message to your body that your new sleep time is 2am so your body begins to adjust, leading to decreased total sleep time and then daytime sleepiness that Monday and you spend the next couple of days trying to catch up!
There are other things that affect our sleep/wake cycles as well. Room temperature in the bedroom is very important. A cool room at night time is important as drops in temperature signals the body it’s time for sleep. As discussed in a previous article, be sure you are eating your last meal 3 to 4 hours prior to sleep and are avoiding heavy snacks before bed. Lastly, consider an afternoon nap for sleep recovery versus sleeping in. Naps do not have as great of an effect on shifting the circadian rhythm as shifting a normal wake time does. Make sure to take a nap early enough in the day and don’t spend too long sleeping. A “power nap” of 20 to 30 minutes is a best practice. What I do not recommend is the use of melatonin to help you fall asleep if you are not going to follow a sleep hygiene routine. It is a waste of money if you cannot work toward creating good sleep habits.
Our circadian rhythm communicates with all parts of our body, it determines specific preferences for eating, moods, body temperature, and release of hormones. Listening to your body and following its cues is an important practice, and sometimes that takes time and patience. Understanding our true and unique circadian rhythm is a key component in our ability to stay in alignment and optimize our sleep quality, quantity and thus our health!