Circadian rhythms are physical, mental and behavior changes that follow a 24-hour cycle within our bodies. This internal clock is controlled by the hypothalamus in our brains, in response to light and darkness, as well as other external cues such as temperature. Nearly every hormone in the human body is released in response to our body’s circadian clock.
Light in the morning hits the optic nerve, transmitting a message of “awake” to the hypothalamus. That translates to an elevation of body temperature and heart rate, as well as other biological changes such as an increase in hormones (including cortisol) and a decrease in sleep-related hormones.
When our eyes are not being hit by light, that signals it is nighttime. The body then produces melatonin and serotonin, two hormones which help us to get drowsy and fall to sleep, and the body temperature drops. Restorative biological processes such as cell regeneration occur, along with many “clean-up and maintenance” processes in the brain and body.
Before electricity, people went to bed when the sun went down and got up early, when the sun came up. Artificial lighting, late-night technology use and our whacky schedules have somewhat detached us from a natural 24 hour cycle, resulting in many of us not getting enough healthy, restorative sleep. Sleep disorders may occur, and insomnia may get addressed with sleep aids, which can further confuse your body’s natural rhythms. Abnormal circadian rhythms have been associated with obesity, depression, diabetes, psychological disorders and seasonal affective disorders.
Circadian Rhythms and Sleep
Teens in particular suffer from sleep deprivation due to disrupting their circadian rhythms. They stay up too late staring into their brightly lit technology, and then have to get up too early for school (likely when their sleep hormones have just kicked in). They drink caffeine throughout the day, and many take melatonin at night. This same unhealthy pattern is seen in many self-proclaimed “night owls” as well.
To further compound the issue, night owls may sleep late on the weekends, thinking they are “catching up”. This further disrupts their natural rhythms, which can lead to mood disorders, irritability, and even a compromised immune system.
Interestingly, high school schedules are not designed to support a teen’s natural behavior and healthy circadian cycle. And many jobs also do not fit well with natural circadian cycles. People tend to be at their peak performance only in very late morning and around dinnertime! How do those peak performance times coincide with your day?
Circadian Rhythm’s Impact to Workers’ Health and Safety
Imagine all the emergency physicians and other night shift workers (long-haul truck drivers, police, and more) who routinely hold life-affecting decisions and activities in their hands – and imagine how fatigued they are.
Major industrial accidents that have been partly blamed on fatigued night-shift workers include the Three Mile Island and Chernobyl nuclear power plant accidents, as well as the Exxon Valdez oil spill. So the safety effects are huge. What about the health effects?
Studies have shown that the effects of an altered circadian cycle may affect how an individual responds to incremental challenges to its immune or metabolic system, such as infection. This has tremendous implications to many people who routinely work against their natural circadian cycles such as late-night shift workers, flight crews, medical residents, etc.!
In one study using mice, researchers put mice through 10 weeks in 20-hour light-dark cycles. After just six weeks, the mice showed less mental flexibility, were more impulsive and got fatter. According to the Science Daily report, the researchers found changes in metabolic hormones, loss in dendritic length and changes to an area of the brain important in executive function and emotional control.
In another study, researchers looking at police officers working night shifts found that officers who most frequently worked the 8 p.m. to 4 a.m. shift had the highest prevalence of metabolic syndrome, a condition that contributes to diabetes, poor heart health, and other health issues.
Continual jet lag: Think about pilots and crew members who routinely fly across time zones. According to the Centers for Disease Control (CDC), crew members with continual exposure to circadian rhythm disruption may experience:
• Disrupted sleep patterns, fatigue, and changes in mood
• Stomach and intestinal symptoms
• Changed hormone levels
• A greater risk of first trimester miscarriage
• A greater incidence of cancer
The importance of circadian rhythm relating to health and safety is actually being studied on the International Space Station by NASA, where artificial environments are made to mimic a normal light/dark pattern. They want to learn how circadian rhythms can be influenced with the healthiest results.
As scientists learn more, today’s work schedules – and school schedules – come into question. Some researchers believe working on “flex-time” in harmony with your natural rhythms could help you perform your best, as well as keep you healthier. What is the best schedule? Many feel that a two-phased approach could be most effective: two phases of sleep, the first being a 6 hour sleep period at night, the 2nd phase being a 1 ½ hour nap around 2-3 in the afternoon. Known as a “siesta” in some countries, there is apparently science behind this tradition!
Circadian Rhythm and Disease
Disrupting your circadian rhythm can impact your hormone levels, especially cortisol and thyroid-stimulating hormones. Studies have shown that sleep-deprivation can cause metabolic disorders, obesity, inflammation, decreased immunity and even impact the hormone insulin, which our bodies use to regulate blood sugar, causing insulin resistance, which is a precursor to diabetes.
Circadian rhythm has such a profound effect on metabolism and health that scientists believe it could influence the treatment of cancers and other illnesses, by programming the body’s clock to respond best to medications. Some medications appear to work best at specific points in the body’s circadian cycle. At Harvard Medical School, researchers have found a way to transplant a circadian rhythm from one species of bacteria to another non-circadian species of bacteria. If a patient were to be given a drug that fluctuates in its efficacy based on circadian cycle, perhaps that cycle can be influenced based on an introduction of manipulated bacteria that are programmed to adjust the body’s rhythm.
Maintain a Healthy Circadian Rhythm for A Healthy You!
You can help maintain your body’s natural circadian rhythm:
• Be consistent in your sleep schedule; even on weekends, keep to your normal wake-up schedule. Do not change your sleep/wake time by more than 2 hours.
• Put the electronics away and lower the lights at least 1 ½ hour prior to bedtime. Use a low-watt bulb for reading.
• Keep your bedroom very dark or wear an eye mask. Even small amounts of light, such as from an electric clock, can slow the pineal gland’s production of melatonin.
• Don’t stare at the clock if you can’t sleep! The light will hit your pineal gland. Also, if you get anxious about the lack of sleep, that will cause your stress hormone (cortisol) to spike.
• Let sunshine (natural light is best!) hit your eyes when you get up, first thing! And try to get at least 15 minutes or so of natural light in the morning if you can.
• If you don’t have sunshine or natural light (due to where you live, weather, etc.), try light therapy with a full-spectrum fluorescent bulb in the early morning.
Take care of your circadian cycle and you are much more likely to get a good night’s sleep and be healthier, too.