World Sleep Day 2023 will commence on Friday, March 17. It incorporates the slogan: Sleep is Essential for Health.Sleep is foundational to our physical, psychological, and social welfare, like a good diet and regular exercise. The president of the World Sleep Society is Dr. Phyllis C. Zee, MD, who provided a valuable message for the 2023 Theme from World Sleep Day. He commented: “Our patients and people of all ages across the world can enhance their overall health and well-being by prioritizing sleep and embracing strategies to improve sleep and circadian health.“
From his words we further understand that our internal “clocks” matter more than we might think.
Circadian rhythms are physical and mental processes that fluctuate across each daily 24-hour cycle. The 24-hour circadian rhythm is important. This rhythm helps us be vigilant during the day and prepare us for sleep during the night. Moreover, it also influences our digestive systems, hormonal activities, and even body temperatures.
Sometimes, our circadian rhythms misalign with our sleep schedule and environment. Knowing more about our sleep-wake cycle and realizing common disruptions to this rhythm can ensure our much-needed sleep quality.
What Are Circadian Rhythms?
Circadian rhythms are 24-hour cycles that are part of the body’s internal clock, running in the background to conduct essential functions and processes. One of the most significant and prominent circadian rhythms is the sleep-wake cycle.
Various systems of the body follow circadian rhythms that are synchronized with a master clock in the brain. However, environmental cues, especially light, directly impact this master clock. This is the reason why day and night cycles influence our circadian rhythms.
When adequately aligned, a circadian rhythm can uphold consistent and restorative sleep. However, when this circadian rhythm goes through disruption, it can create serious sleeping problems, including insomnia. The research also reveals that circadian rhythms play an integral role in diverse aspects of physical and mental health.
How Does Circadian Rhythm Work?
Circadian rhythms optimize the body’s processes at various points during a 24-hour period. The term circadian originates from the Latin phrase “circo diem,” which implies “around a day.”
Circadian rhythms exist in all types of organisms. For instance, they help flowers open and close at the right time. They also prevent nocturnal animals from leaving their shelters during the daytime to avoid exposure to more predators.
In individuals, circadian rhythms coordinate biological and mental systems throughout the body. For example, the digestive system produces proteins to match the typical timing of meals. Similarly, the endocrine system regulates hormones to optimize normal energy expenditure.
A master clock—i.e., a circadian pacemaker located in the brain—connects the circadian rhythms throughout the body specifically, it is found in the suprachiasmatic nucleus (SCN)which is in a part of the brain called the hypothalamus. At various times during the day, clock genes7 in the SCN transmit signals to regulate bodily activities.
The SCN is highly sensitive to light, which serves as a critical external cue influencing the signals sent by the SCN to regulate internal body clocks. Therefore, the day and night cycle closely relates to circadian rhythms. Several other cues, like exercise, social activities, and temperature, can affect the master clock. However, light is the most intense influence on circadian rhythms.
Is a Circadian Rhythm the Same As a Biological Clock?
Biological clocks regulate the timing of bodily processes, including circadian rhythms. A circadian rhythm affects a biological clock, but not all biological clocks are circadian. For instance, plants adjust to varying seasons using a biological clock with timing distinct from a 24-hour cycle.
How Does Circadian Rhythm Affect Sleep?
When people discuss circadian rhythm, it is most often in the context of sleep. Thus, the sleep-wake cycle is one of the most transparent and critical examples of the significance of circadian rhythms.
During the day, light exposure causes the master clock to send signals for our generate alertness and help keep us awake and active. Then, as night falls, the master clock initiates melatonin production, a hormone that promotes sleep. Next, it keeps transmitting signals that help us stay asleep through the night.
In this manner, our circadian rhythm aligns our sleep and alertness throughout the day and night. Moreover, it also creates a regular cycle of restorative rest that enables enhanced daytime activity.
What Does Circadian Rhythm Affect Besides Sleep?
While the sleep-wake cycle is the most prominent circadian rhythm, the 24-hour internal clocks are integral to all body systems.
Several studies continue to uncover details about circadian rhythms. However, the evidence has connected them to metabolism and weight by regulating blood sugar and cholesterol. Circadian rhythms influence mental health, including the risk of psychiatric illnesses like depression and bipolar disorder. Moreover, any disruption in circadian rhythms can have the potential for neurodegenerative diseases like dementia.
There are indications that circadian rhythms can important influence the immune system and DNA repair processes to prevent cancer. In addition, early-stage research indicates that circadian cycles can impact the effectiveness of anti-cancer drugs. Thus, new medications may be able to harness biological clocks to eradicate cancer cells.
What Can Disrupt a Circadian Rhythm?
The research concludes that continuous or occasional disruption of sleep patterns can create circadian rhythm sleep disorders. The disruption results from malfunctioning in our “internal body clock” or a mismatch between this clock and the external environment. The external factors include social and work requirements, which might impact our sleep timing and duration. This circadian mismatch causes problems at work, school, and social activities. Various situations triggering a circadian rhythm sleep disorder include:
Daylight Saving Time: About a quarter of people worldwide experience time shifts related to daylight saving time. Although these shifts only move the clock by one hour, research shows a short-term rise in fatal car accidents, workplace injuries, and heart attacks. These eventualities may occur due to circadian disruptions.
Jet Lag: Jet lag occurs when an air traveler’s circadian rhythm becomes out-of-sync with the destination time zone. It becomes even more severe for travelers crossing multiple time zones. Consequently, a traveler feels sleepy during the day and awake at night.
Shift Work: Shift workers typically operate night or early morning shifts. They often experience circadian rhythm disruptions as they work when it is dark outside and sleep during daylight hours.
What Are These Types of Circadian Rhythm Sleep Disorders?
Delayed Sleep Phase Disorder
During this sleep disorder, we go to sleep and wake up more than two hours later than what is typically considered a normal sleep-wake cycle. For instance, we are a “night owl” who may not fall asleep until 2 am but then sleep until 3 pm. Other common features of delayed sleep disorder are as follows:
- we’re often most vigilant, productive, and creative late at night.
- If forced to wake early, we are sleepy during the day.
- People perceive we as lazy, unmotivated, or a poor performer who is always late for the morning responsibilities.
- Adolescents and young adults usually endure this disorder.
- It may run in families.
Advanced Sleep Phase Disorder
During this sleep disorder, we fall sleep in the early evening (6 to 9 pm) and wake up in the early morning (2 to 5 am). Other common features of advanced sleep phase disorder are the following:
- We complain of early morning awakening or insomnia and are sleepy in the late afternoon or early evening.
- Middle age and older adults typically endure this disorder.
- It may run in families.
Jet Lag Related Disorder
In this disorder, our body’s internal clock disrupts due to long air travel to a destination two or more time zones away. This sleep-wake cycle disruption makes adjusting and functioning in the new time zone challenging. Eastward journey is more difficult than westward travel because delaying sleep is easier than advancing.
Shift Work Disorder
We may have this disorder if we frequently rotate shifts or work at night. These work schedules conflict with our body’s natural circadian rhythm, making it hardly to adjust to the transformation. Shift work disorder creates a constant or recurrent sleep interruption pattern resulting in insomnia or excessive sleepiness. This sleep disorder includes individuals who have night or early morning shifts.
For instance, extended shift durations and interrupted sleep are integral parts of anesthetists’ and intensivists’ professional lives. Despite recommendations in the USA and Europe to limit work hours, the amount worked can still lead to acute and chronic sleep deprivation may still present a potential hazard to patients’ safety and doctors’ health. Thus, sleep deprivation of over 24 consecutive hours produces equivalent to a blood alcohol concentration of 1 g/L on simulated driving performance. For example, the junior residents working over 24-hour shifts in ICU made 36% more serious medical errors than those working shorter shifts.
Extensive literature shows adverse effects of sleep deprivation on laboratory and non-medical settings, such as psychomotor vigilance tasks. In a large retrospective study showed that sleep deprivation increases complication rates during surgical procedures. Using simulated laparoscopic surgery, they demonstrated that sleep deprivation increased the surgery length and the error rate during complex surgeries. In a self-reporting survey, 86% of New Zealand anesthetists declared that errors in patient care happened due to fatigue. Furthermore, the study linked fatigue with more frequent major pharmacological incidents (i.e., syringe swap, wrong drug, wrong dosage).
Irregular Sleep-Wake Rhythm
This sleep disorder creates an undefined sleep-wake cycle. As a result, we may take several naps during a 24-hour period to tackle this disorder. Symptoms include ongoing (chronic) insomnia, excessive sleepiness, or both. People with neurological conditions endure this disorder, such as dementia, in nursing home residents, children with intellectual disabilities, and those with traumatic brain injuries.
Non-24-Hour Sleep-Wake Syndrome
We keep the same sleep and awake time during this sleep disorder, but our “internal clock” is longer than 24 hours. As a result, the actual sleep-wake cycle varies daily, with one to two hours of delays each day. This disorder occurs most commonly in visually-impaired individuals.
What Are The Symptoms of Circadian Rhythm Sleep Disorders?
- Insomnia (difficulty falling or staying asleep).
- Excessive daytime drowsiness.
- Difficulty waking up in the morning hours.
- Sleep loss.
- Depression or anxiety.
- Stress in relationships.
- Poor work/school performance.
- Inability to meet social obligations.
How Are Circadian Rhythm Sleep Disorders Treated?
Treatment options for circadian rhythm sleep disorders vary based on the disorder type and how it affects quality of liveing. The healthcare provider develops a personalized treatment plan, which improves our success chances. Most treatment plans necessitate a combination of approaches. Treatment options include:
Lifestyle and Behavior Therapy
This approach encourages transformations to improve sleep and develop good sleep habits. Good sleep habits include maintaining regular sleep-wake times, even on weekends and vacations. In addition, we can avoid naps (exception: shift workers) and develop a regular exercise routine (avoid high-intensity exercise within one hour of bedtime). Finally, the therapy includes avoiding alcohol, caffeine, nicotine and stimulating activities within several hours of sleep.
Bright Light Therapy
Bright light therapy helps treat advanced or delayed sleep. The timing of this therapy is critical and requires guidance from a sleep specialist. Good light treatment works by resetting the circadian clock to be more in sync with the day-night cycle. Thus, we need high-intensity light (2,000 to 9,500 lux), and exposure timing vary from one to two hours.
Exposure to bright light in the morning may help if we have a delayed sleep disorder. We should also decrease our light exposure at night by reducing indoor lighting and avoiding bright TV and computer screens.
Experts suggest some medications, such as melatonin, wake-promoting agents (modafinil [Provigil®]) or caffeine, and short-term aids to adjust and maintain the sleep-wake cycle. For example, they approved Tasimelteon (Hetlioz®) to treat non-24-hour sleep-wake disorder.
This therapy uses progressive advancement or delay (three hours/alternate day) of sleep time, depending on the disorder’s type and severity. This type of treatment requires a firm commitment by us and our partner, as it takes weeks to successfully fix the sleep-wake cycle. After achieving the desired schedule, we must keep this regular sleep-wake schedule.