Circadian Rhythm & Your Health
Are you a Night Owl? Or a Morning Lark? And how is that connected to your mood and longevity?
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Do you find that you are most creative and productive in the evening like a Night Owl? Do you find yourself naturally waking at sunrise like a Morning Lark no matter whether it’s a workday or not?
Growing up I always thought I was a “Night Owl” finding that my brain would seem to wake up as the day moved on with my best work coming by moonlight. But when I started working, I needed to shift my routine or circadian rhythm for those early starts, however on holidays my body always seemed to go back to my “night-owl” routine. I stay in my “Morning Lark” cycle, positive mood and energized groove by getting out in the great outdoors first thing in the morning.
Did you know that your circadian rhythm that influences your sleep-wake cycles is genetically set? You may have these natural tendencies like me that may be annoying but do get a full night’s sleep, wake rested and don’t interfere with your overall health. Although genetics determine if you are a “Night-Owl” or a “Morning Lark” you can shift your rhythm by light therapy like I did.
However, Have you ever found that in the winter you tend to feel tired upon waking even after a full night sleep? Can’t sleep so find yourself watching Netflix until the wee hours of the morning? OR Are not hungry during mealtime yet are hungry at night?
If so, you may have a Circadian Rhythm Disorder.
What is circadian rhythm?
Your circadian rhythm is a 24-hour “internal central clock” that is reset every day in the human brain that regulates physical, mental and behavioral changes according to the time of the day. In addition to the central clock of the brain, each of your cells in various organs contain a “peripheral clock” that takes its orders from the central clock. Together they help to regulate the activity of approximately 40 percent of your genes that influence your: sleep wake cycle, hormone release, hunger, digestion, body temperature, heartrate, blood pressure, neurological function, obesity, lifespan and more.1 This rhythm is influenced by environmental cues such as light – in particular daylight and temperature so that when its sunny out you have a desire to stay awake vs if its dark and cold out you have a tendency to get drowsy and hibernate.
Why is your circadian rhythm so important?
Emerging new research from MIT indicate that a well-functioning circadian rhythm is correlated with a longer lifespan.2 Other studies propose that we may be able to influence longevity and prevent diseases of aging by enhancing circadian function.3 Without a properly functioning circadian rhythm your body is prone to exhaustion, mood disorders, sleep issues, weight gain, type II diabetes, cardiovascular disease, cancer, neurogenerative disease including memory consolidation issues (the formation of long-term memories that occurs during sleep) and other physical illness. 4-6 Everyone’s circadian rhythm is genetically unique to them which is why some people tend to be “night-owls” while others are “morning-larks “. The key is to live a lifestyle that promotes a balanced circadian rhythm with regular habits including by going to bed and waking at the same time.
How does circadian rhythm work? And how is it impacted by light?
The control of your circadian rhythm is a function of multiple genes in the DNA called circadian “clock genes” that code whether you wake up early or late and are plugged into every cell in your body. There are more than 10 clock genes that produce proteins that help to determine whether you are a “night owl” or a “morning lark”. The speed of how quickly these proteins degrade in the cytoplasm determines if you are going to be an owl or a lark. One such gene is CLOCK (Circadian Locomotor Output Cycles Kaput), a protein that regulates the circadian cycle, also has an anti-aging effect, by promoting chromatin stability.7
Scientists have learned that the effects of light go well beyond visual function. It has been discovered that there is a non-visual pathway from the eyes to the brain, totally independent from vision. Your daytime hormones such as cortisol and nighttime hormones including melatonin are managed by light.
For a quick refresher for those who want to take a deeper dive on light and the electromagnetic spectrum:
- Ultraviolet (UV): < 380nm
- Visible Spectrum: 380-780nm (High Energy Visible Blue Light 380-500nm with the sun as the highest emitter)
- Infrared Radiation (IR): >780 nm
Virtually every cell in the body contains its own circadian clock machinery; the master clock that orchestrates and synchronizes them all is a tiny brain region called the suprachiasmatic nucleus (SCN)(also known as the “third eye”) in the hypothalamus. When you are exposed to blue light the retinal ganglion cells that contain stimulating melanopsin are activated. Information about light levels (natural and artificial through indoor lights, computers and other IT) is sent to the SCN via that retinohypothalmic tract in the hypothalamus. The hypothalamus then directs the pituitary to produce or reduce melatonin. A balanced circadian rhythm is promoted by exposure to strong natural light throughout the day and evening light-dark. The SCN is like a conductor coordinating all the cellular clocks in the body via the endocrine system that produces a variety of hormones over a 24-hour time period to ultimately control the circadian cycle.
The right light at the right time is critical in governing the “body clock”, however not all light is equally effective in having a positive effect or disrupting it. Scientists have determined that it is short wavelength (around 484nm) blue light in the spectrum that influences circadian rhythm the most. Natural daylight has a large blue component as well artificial light sources such as “cold” fluorescents, metal halide lamps and many LEDs. These sources are the most effective in setting your body clocks whereas “warm” lamps such as HPS, LPS and tungsten halogen are the least.
What are circadian rhythm disorders?
Circadian rhythm disorders are a group of conditions that occur when your circadian rhythm – most commonly your sleep-wake cycle is not properly aligned with your environment and interferes with your daily activities.
Common circadian rhythm disorders include:
- Jet Lag or Rapid Time Zone Change Syndrome: Most of you have experienced jet lag the occasional time when you travel across time zones, however for those in which it is a regular occurrence you know all too well the sleepiness and lack of daytime alertness that is common. This typically is amplified with each time zone crossed, especially when traveling toward the east.
- Shift Work Sleep Disorder: This disorder affects those who frequently work shift work or work at night. For some their genetics allow an easier transition while others experience a dramatic impact meaning that they can get up to 4 hours less sleep a night compared to the average person.
- Delayed Sleep Phase Syndrome (DSPS): This is a shift in circadian rhythm and a disorder of sleep timing. Those with DSPS are wired to fall asleep very late resulting in a difficult time getting up in the morning as opposed to “night owls” who choose to go to bed late. Research shows that there is a higher incidence of depression in people with DSPS.8 DSPS is common in teens and young adults.
- Advanced sleep phase syndrome (ASPS): This is a disorder in which a person goes to sleep earlier and wakes earlier than desired. For example, they might fall asleep between 6 and 9 p.m. and wake up between 1 and 5 a.m
- Irregular Sleep-Wake Rhythm Disorder (ISWRD): With this disorder, there is lack of a circadian rhythm pattern of sleep and wake. Individuals will sleep at variable times throughout the day and night. They may often sleep is a series of naps of variable length during a typical 24-hour day.
- Non-24 Hour Sleep-Wake Rhythm Disorder (N24): In this condition an individual’s biological clock is not aligned with a 24–hour day. N24 sufferers will typically have their sleep time gradually delaying by minutes to hours every day. This often affects those who are blind due to lack of the light-dark cycle.
What are the signs and symptoms of circadian rhythm disorders?
Symptoms that have lasted for three months or more may indicate a circadian rhythm disorder. One of the first symptoms is often sleep difficulties.4 Common symptoms of circadian rhythm dysfunction include:
- Consistent difficulty falling asleep, staying asleep, or both
- Nonrestorative sleep (feeling tired even after getting enough sleep)
- Daytime sleepiness or sleepiness during shift work
- Fatigue, exhaustion, lethargy
- Impaired performance
- Poor concentration
- Decreased alertness
- Reduced psychomotor coordination
- Impaired judgment and trouble controlling mood and emotions
- Aches and pains, including headaches
- Digestive distress
- Stomach problems, in people who have jet lag disorder
Ultimately sleep deprivation can change how your brain perceives risky situations and you may underestimate the risks and overestimate the rewards of situations. This may lead to riskier behaviors than what you would normally choose when well rested leaving yourself and others at an increased susceptibility to danger. Thus, keeping your circadian rhythm in check is important to stay mentally and physically healthy.
How does your circadian rhythm impact your mood?
Irregular circadian rhythms send mixed messages to the body. A study published in The Lancet Psychiatry has found that disruptions to your internal clock may increase the risk of mood disorders including depression, anxiety, bipolar disorder and seasonal affective disorder (SAD) by up to 10 percent. 9 In particular if one’s circadian rhythm is dysfunctional, there is a greater association within mood disorders towards major depressive disorder and bipolar disorder. It has been suggested that those who are night-owl type may have a greater predisposition to mood disorders.10 It was also found that night owls tended to be lonelier and more unhappy. Early risers tend to have healthier breakfasts and are less likely to procrastinate– all habits of highly successful people and great reasons to go to bed earlier.
Scientists have determined that shift workers are 40% more likely to develop depression than daytime workers.11 The severity of one’s depression correlates with the degree of disorder of the circadian and sleep rhythms. Anxiety has also been found to be higher in shift workers and those with jet lag. Researchers believe that changes in circadian rhythm as a result of seasonal changes in the length of daylight are linked to SAD.
Are there other concerns linked to circadian rhythm disorder?
Circadian rhythm disorders may increase your risk for the following health conditions:12-19
- Immunity: a compromised immune system – even one night’s lost sleep can reduce the activity of white ‘killer cells’ in the blood by up to 28%
- Cardiovascular Diseases: atherosclerosis or stroke
- Mood Disorders: including irritability, depression, anxiety, bipolar and SAD
- Addictions: increased risk
- Socialization: decreased socialization, communication skills and sense of humour
- Cognitive and Behavioral Disorders: decreased attention, concentration, motor skills, ability to multi-task and memory with increased risk-taking, and less adaptation to stress
- Creativity & Productivity: reduction
- Digestive Conditions: as circadian rhythm disorders may influence signaling from the brain to the GI tract and may increase inflammation increasing the risk of stomach ulcers, gastroesophageal reflux disease (GERD), and irritable bowel syndrome.
- Hormone Imbalances: including PMS and fertility
- Metabolic Disorders: which may lead to diabetes, metabolic syndrome and weight difficulties – deficiencies in sleep are linked to a reduced production of leptin, your “I’m full hormone” and an increased production of ghrelin, your “hunger hormone”
- Sleep: amplification of other sleep disorder such as sleep apnea
- Cancer: female night-shift workers i.e. nurses have been found to have a higher incidence of breast cancer than nurses working day shifts potentially due to the lack of exposure to bright daytime light impacting growth hormone production
What are the causes of circadian rhythm disorder?
You may have a higher risk for circadian rhythm disorders because of internal factors such as your age, your sex, family history and genetics, and certain medical conditions that affect your brain or vision. External factors such as your lifestyle habits, environment, and occupation can also increase your risk. The most common causes of circadian rhythm disorder include:
- Sunlight: reduced of exposure to sunlight (especially in winter) during the day
- Blue Light: excess exposure to artificial light emitting diodes (LED) from digital devices i.e. blue light from cell phones, TVs, computers and even modern street lighting that is metal halide or LED which have more blue in their spectra (research by the LRC in the USA found that one hour’s exposure to 100 lux of light from a “cold” (6900K) street light can suppress melatonin levels in subjects by up to 15%. More than ever – and at younger ages – our electronic media usage is at an all-time high with more than 50% of our day increasingly spent on digital devices.
- Sleep: irregular sleep patterns (jet lag, unhealthy sleep habits, etc.) or inability to get a deep sleep
- Age: the aging process increases the risk of circadian dysfunction due to changes in the brain. Teens are more prone to delayed sleep-wake phase disorder up until the age of about 20 while older adults have an increases risk of the reverse advanced sleep-wake phase disorder.
- Sex: men are more likely to have advanced sleep-wake phase disorder than women while women are more likely to have circadian dysfunction at certain stages of life such as hormonal changes of pregnancy, post-partum and menopause
- Job: People who work during the night have a higher risk for shift work disorder. Jet lag disorder is more common in pilots, flight attendants, athletes, and people who travel often for business.
- Drugs & Alcohol: excess alcohol, hypnotics, and stimulants (i.e. caffeine)
- Eating: at an irregular time of day (too late at night)
Select Medical Conditions:
- Autism spectrum disorders (ASD)
- Genetic conditions, that impact your brain or hormones such as Smith-Magenis syndrome (a genetic condition that impacts melatonin production), Angelman syndrome (a condition that leads to developmental problems), and Huntington’s disease (a rare disease that causes the progressive breakdown (degeneration) of nerve cells in the brain)
- Conditions that affect eyesight, such as blindness and macular degeneration. This raises the risk for non-24-hour sleep-wake rhythm disorder.
- Conditions that cause damage to the brain, such as traumatic brain injuries (TBIs), strokes and brain tumors
- Mental health conditions, such as bipolar disorder, major depression, obsessive-compulsive disorder, and schizophrenia. This raises the risk of delayed sleep-wake phase disorder.
- Neurodegenerative diseases, such as Alzheimer’s disease, dementia, and Parkinson’s disease. These conditions can damage brain cells that process light and other signals from the environment and can increase your risk for irregular sleep-wake phase disorder.
What are the key circadian rhythm hormones?
The hormones cortisol, melatonin and serotonin rise and fall based on your circadian rhythm.
- Cortisol: is a hormone produced by the adrenal glands that your body produces more of in the morning. In acute stress cortisol can make you more alert, however in chronic stress excess cortisol can contribute to increased weight gain, reduced overall wellness, inflammation and eventually fatigue.
- Melatonin: is a hormone that is produced at night with darkness and suppressed during the day that makes you sleepy.
- Serotonin: is a hormone that promotes a positive mood and contributes to optimal sleep.
Can you shift your circadian rhythm?
Growing up the ideal schedule for me was to go to bed at 12 midnight and wake at 8 am. I always thought I was a “night owl”. In high school and university my brain would seem to wake up and my best work would come by moonlight. Mornings, I was thankful that my school started at 9 am, giving me time to awaken slowly and get going. But, at the age of 29, I mentored with Dr. Don Warren a well-respected ND 20 years my senior, who was early-to-rise and early-to-bed. So I shifted my routine to wake with the sun to get in a morning workout and to get to bed earlier to balance my busy days. Then at the age of 38 after having 2 highly energetic kids, I found myself waking even earlier to sneak in my “self-care” workout at 6 am to fit in the morning family routine and then scoot off to work! Although it would have been nice to stay cozy in bed, once I was up, I really enjoyed my time. Was it that I was really a “morning lark” and didn’t know it, or did I actually change my circadian rhythm?
Your circadian rhythm is genetically determined but can be influenced by your environment such as by light. So you can shift your biological clock to accommodate your lifestyle requirements such as an early work schedule or late-night shift work but you may find that your body quickly goes back to your genetic predisposed rhythm when allowed to do so like on vacation. If possible, it’s great when you can support your natural rhythm and build your lifestyle around what comes natural to you. For example choosing a starting work schedule that is shifted a few hours later for those who are “night-owls” or working earlier for those of you who are “morning-larks”. The key is to not burn the candle at both ends and target the full 8hrs of quality sleep overall.
What are the investigations and lab tests to help diagnose circadian rhythm disorders?
Your integrative doctor may recommend the following tests:
- Four Point Cortisol Test: that measure your circadian cortisol rhythm by tracking your cortisol upon rising, midday, afternoon, and bedtime to determine your levels throughout the day in your blood or saliva
- Melatonin: can be assessed in your blood or saliva
- Hormones: to review if perimenopause or menopause is influencing your sleep-wake cycle
You may then be referred to your medical doctor for the following tests:
- Sleep Studies: usually performed in a sleep lab, monitoring a person’s sleep, level of oxygen, number of times one stops breathing and snoring.
- CT Scan or MRI: may be done to rule out neurological diseases, sinus infections or blockages of the airway
Other general self-tracking measurements include:
- Epworth Sleepiness Scale. A questionnaire that rates responses to eight situations, on a scale of 0-3, of their associations with sleepiness.
- Body Temperature: which varies according to your sleep cycle
- Sleep Logs: to track your sleep-wake cycles including when and how long you slept
- Sleep Trackers: the Fitbit for example estimates your sleep stages using a combination of your movement and heart-rate variability (HRV), which fluctuate as you transition between light, deep and REM sleep stages
- Actigraphy: a motion sensor worn on a person’s non-dominant wrist for three to fourteen days to measure sleep-wake cycles
What are key treatment strategies for circadian rhythm disorders and shifting your biological clock?
Your solutions will vary depending on the root cause of the circadian rhythm disorder or goal for achieving a phase shift or shifting your biological clock. A few helpful strategies may include:
1. Light Therapy: Light is the most effective signal in the environment to help balance your circadian rhythm. Timing is everything. You may need more sunlight in the day and less artificial light at night from electronic devices and TV screens. The goal is to expose yourself to light to stimulate sunrise at the time you want to set as “morning” in your brain. In the evening, start diming your lights to reduce light exposure 2 hours prior to what you want to set as your “bedtime”. If you are trying to phase shift later, get some blackout curtains and delay sunlight exposure. Natural light is best however you can also use SAD lamps or light therapy lamps that are easy to put in your workspace. If you need extra motivation you can also get a dog that needs outdoor time, adds more laughter in your life and provides you with companionship.
2. 30 Minute Morning Walk: According to research by Oxford University, a 30-minute walk in the morning provides better health results that artificial light. A sunny day is equivalent to 100,000 lux while indoor lighting only provides about 300 lux. The average person needs exposure to 1000 lux to enjoy the maximum benefits. Even a cloudy day provides significant light exposure.
3. Light Therapy Lamp: Look for 10,000 lux full spectrum white light without UV light therapy devices. For best results place 12-18 inches away at eye level or higher, keeping at an angle and not staring directly at the light. Use upon rising for 30 minutes for general circadian rhythm balance. The closer the light therapy exposure is to your melatonin peak (4 am) the more effect it will have in shifting your circadian clock. To advance clock timing target light therapy AFTER your melatonin peak i.e. 6 am promoting you to wake up earlier. To promote delaying your clock timing (delaying the onset of sleep) target light therapy BEFORE your melatonin peak i.e. 8 pm.You can also use at other times of the day for a pick-me-up instead of grabbing another cup of java!
4. Window: If possible, work or spend time near a window. One study found that those with a window were better rested, had a better sense of health, double the amount of alertness and got 46 minutes more sleep a night on average. Some studies show that people feel better, are more alert and work best at an ambient light level of about 100 cd/m2.
5. Light-Blocking Equipment: glasses, screen filters, or smartphone apps can help dim the light from your electronic devices. For shift workers, wearing light-blocking glasses when you are outside during the day may help while for those with sleep difficulties using any of the light-blocking devices during the evening can help before bed.
6. Sleep: Develop a regular bedtime routine that targets 7-9 hours of quality sleep. To help reset your sleep-wake cycle developing a routine for your sleep-wake times will help bring your internal clock in check. You can keep in mind your genetic tendency to be a “night-owl” or “morning-lark” and either shift your circadian rhythm to fit your life OR shift your life to fit your natural circadian rhythm. For example, if you are a “night-owl” you may find choosing a job that allows you the flexibility of starting later feels easier to maintain. Additional tips include:
- Naps: Avoid long naps during the day as well to prevent interfering with your nighttime sleep.
- Wind down: Reduce screen time and bright lights at least 60 to 90 minutes before bedtime to reduce daytime cortisol. Try reading a book in dim light, listening to a relaxing podcast, guided meditation or soothing music.
- Environment: Sleep in a completely dark room without any lights (including TVs) and a cool environment (60-70 degrees Fahrenheit)
- Melatonin: If needed, check with your health care provider if melatonin is the right fit for you in situations where more help is needed. It works in the opposite manner to light, thus taking melatonin later in the night (before bed) advances your circadian rhythm, while taking it earlier in the day will delay your circadian rhythm. Set a goal of taking melatonin two to three hours before your desired time to go to bed.
7. Exercise: research has found that exercising in the morning or early afternoon (7 am to 4 pm) shifts your clock earlier, whereas exercising at night (7 pm to 10 pm) can delay your rhythm.
8. Meals: scientists have discovered that phase shifting three meals can achieve a delay in circadian rhythm and vice versa. Phase shifting one meal does not have the same effect. A regular meal schedule is particularly helpful for those who work shift-work or have an irregular sleep schedule.
9. Socializing: it has been found that groups are better able to regulate their circadian rhythm than individuals – so if you are trying to change a habit whether its exercise, or phase shifting, then find yourself a circadian rhythm buddy!
10. Limit Stimulants: like caffeine, alcohol, nicotine and some medications, especially close to bedtime.
11. Smartphone Apps: can be used to help you understand, shift, maintain or optimize your circadian rhythm. A few examples include:
- My Circadian Clock: MyCircadianClock is apart of a research project. It allows you to track when is optimal to eat, exercise, and sleep in depth to increase your circadian rhythm. Download for AppleDownload for Android
- Solar Clock: Circadian Rhythm: Uses the solar clock and your circadian rhythm to notify you when ideal times are to awake, workout and sleep. It includes an alarm clock to keep you in check with your circadian rhythm. Download for Android
- Sleep Cycle Smart Alarm Clock: This app focuses on coaching you to a better sleep. It includes a sleep aid to help you fall asleep, a smart alarm that wakes you up when in a light sleep for better energy, an analysis of your sleep, and snore detection to show how much you snore. Download for AppleDownload for Android
Special Tips for Shift Workers, Jet Lag, Dementia and Post-Surgical Recovery
The following steps may help prevent shift work disorder:
- Sleep Schedule: develop a sleep schedule on your days off that is the same as your sleep time on days that you work to avoid multiple frequent changes to your sleep-wake cycle.
- Mini Naps: take a short nap before your night shift to help reduce sleepiness at work
- Regular Schedule: avoid multiple schedule switches between day and night shifts, where possible
- Yellow-Tinted Light in Night-Shift Workplaces: may help circadian adaptation
- Blue Light Filtering Glasses: to reduce blue light in the daytime
The following steps may help prevent jet lag disorder:
- New Sleep-Wake Cycle with Light Therapy: shift into your new time zone a few days before traveling across several time zones to match the time at your destination. You can use light therapy to expose yourself to light that corresponds to your new time zone “morning”. More specifically you can use light therapy according to your flight path:
- Eastward Flights: expose yourself to bright light therapy (natural or artificial) in the morning after your normal (home) wake time and dim light prior to bedtime
- Westward Flights: expose yourself to bright light therapy in the evening before normal bedtime (home) and dim lighting after wake time
- Buffer: if possible, arrive at your destination a few days before an important event to allow you gradually adjust to the local time. Your body adjusts to the time at your destination at a rate of 1 to 1.5 time zones per day.
- Outdoor Light: enjoy your new destination by spending plenty of time outside, which may help shorten your jet lag.
The following may help dementia, Alzheimer’s and post-surgical recovery:
- Certain types of circadian therapy may help improve night-time sleep patterns, slow cognitive decline, reduce depression, agitation and aggressiveness in those with dementia or Alzheimer’s disease. Research shows that exposure to bright morning light (2500 lux for two hours) may improve dementia or Alzheimer’s symptoms as well as improve recovery time in hospitals with far less medication.
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