Massa Mohamed Ali, HBSc Candidate, University of Toronto
Circadian rhythms provide the body with a 24-hour cycle to follow changes in the environment. A term with Latin origins, circadian means "around a day," referring to the cyclical nature of the 24-hour clock. Most living things have these rhythms that respond primarily to light exposure. In humans, they form our internal body clock, determining our energy and alertness levels. This influences our internal processes and behavior, including digestion, hormone release, body temperature, sleep patterns, mood, and more.
Researchers have used fruit flies, mice, plants, and many other organisms to study circadian rhythms. From this data, scientists have established that different environmental stimuli can change when the body expresses certain genes responsible for regulating circadian rhythms. In mammals, the Period and Cryptochrome genes are affected by the timing of light exposure, temperature, food, exercise, and social connection.
With the clocks moving forward for spring, many of us may be facing some disruptions to our sleep-wake cycles as we adjust to a new schedule. This can be disorienting, especially when it lasts for a prolonged period. Listening to your body and its cues is vital to ensure that you perform optimally during the day. This starts with knowing your circadian cycle. Not only does this tell you when you are more likely to be alert, but it will also give you the flexibility to gradually change your circadian cycle. Whether you know you will be traveling and jet-lagged, or have a late gathering planned with friends, or will be affected by the daylight savings time change, you can use the information in this article to help you better align your sleep and activity schedules.
Determining Your Circadian Cycle
To identify what your current natural sleep-wake cycle is, observe your wake time without an alarm for 4-7 days. You can also use the concept of temperature minimum, as suggested by neuroscientist Andrew Huberman. He describes that the body reaches its lowest temperature about 90-120 minutes before one wakes up in the morning. He mentions that viewing light, exercising, and eating 4-6 hours before this temperature occurs in the body delays the body's circadian clock. However, viewing light, exercising, and eating 4-6 hours after this temperature makes one more inclined to wake up earlier.
For instance, if one normally wakes up at 7 am on average, their temperature minimum will fall at about 5 am. To shift their clock forward, they would need to consistently view bright sunlight, exercise, and eat between 9-11 am. To shift their clock backward, they would do this between 9-11 pm the day before. Generally, it is recommended to make changes to one’s circadian clock in 15-minute intervals. These transitions are also made easier with better sleep quality.
Temperature is a great indicator of our cycle, as the body naturally increases its temperature upon waking and decreases it closer to bedtime. The cells in different parts of the body interpret this signal in unison and carry out reactions accordingly. This method has been effective at reducing symptoms of jet lag and helping people adjust to new time zones 2 days earlier than expected.
Aside from these techniques, there are many tracking devices that now allow the efficient detection of sleep-wake patterns. Additionally, new research now suggests that blood biomarkers can be used to determine one's stage of the circadian cycle.
Light Exposure
Several studies have shown the significant impact of the duration, intensity, and color of light on the body's circadian clock. According to the Centers for Disease Control and Prevention, viewing bright sunlight within the first hour of waking is essential for staying alert throughout the day, getting better sleep at night, and maintaining overall well-being. A simple 10-15 minutes of sunlight, even on a cloudy day, can help individuals become more in tune with nature and induce the subconscious biological processes required for a balanced circadian rhythm.
Effects of Light on the Body
When light hits our retinas, intrinsically photosensitive retinal ganglion cells (ipRGCs) send input to neurons in our suprachiasmatic nucleus (SCN) in the hypothalamus. This area relays time-of-day information to other parts of the brain to coordinate behaviors accordingly. This area also controls the production of hormones like melatonin, which promotes sleep. Cortisol is another hormone that is released when viewing more sunlight in the morning. As it leaves the adrenal glands, it signals an increase in heart rate and temperature to get the body ready for the day. In a recent study from the International Journal of Environmental Research and Public Health, the release of cortisol was shown to act as an internal timer for the release of melatonin. This shows that early light exposure determines how well the circadian rhythm flows throughout the day.
LIGHT IN THE EVENING
As for the evening, scientists recommend avoiding bright light between 10 pm and 4 am. It is also recommended to use dimmer lights and position them lower in one’s visual field to limit the activation of the circadian cells in the retina. Best practice is to find the minimum amount of light you can have to see comfortably. This is because studies show that viewing bright artificial light during the later part of your circadian cycle is associated with disruptions in blood sugar, lower sleep quality, higher rates of depression, reduced amounts of dopamine, and a sense of jet lag right in your own home. Ideally, one should not interact with screens between 60-90 min before sleeping.
NUTRITION AND EXERCISE
Our eating and exercise habits also influence our circadian clocks. Although they are both influenced by light exposure, our bodies learn to anticipate food and activity. With regular mealtimes throughout the day, our nervous and endocrine systems control our energy levels. More specifically, the arcuate nucleus area of the hypothalamus drives hunger by regulating the release of hormones from the pituitary gland. When we limit eating to the times of day that we are most active, we better align our circadian cycle for optimum energy performance. This helps us listen to our body's natural cues. Additionally, a study published in the Journal of Physiology found that exercise at a particular time of day leads to wakefulness at around that time after about 3 to 7 days of forced activity, suggesting that we can train ourselves to have more energy at certain times of the day.
Understanding how your internal clock works can help you synchronize it with your daily activities and use your time most efficiently. This allows you to have more control over your day, especially with the recent daylight savings time change. While light exposure remains fundamental, matching the times you eat with the times you are most active is also beneficial to regulate your internal clock. Sticking to a consistent feeding, sleeping, waking, and exercise schedule, and making gradual changes if needed, will help you listen to your body and feel your best throughout the day.
For all the reasons mentioned above and more, brain damage following a concussion can be very frustrating. Light sensitivity, cognitive decline, and motor deficits can all affect one's circadian rhythm, which determines the course of their day. Neurovine is actively working to make the concussion recovery process easier, faster, and safer. Not only does this provide patients with the care they need, but it also regulates their circadian cycles for better performance! To find out more or get involved, give us a call, email, or contact us. We look forward to hearing from you!
ADDITIONAL RESOURCES:
Let Us Know What You Thought about this Post.
Put your Comment Below.