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The Role Of Sleep And Circadian Rhythms In Neurological Health

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The Role Of Sleep And Circadian Rhythms In Neurological Health

The body's circadian rhythm, natural 24-hour clock, and associated sleep patterns are integral to health and well-being. Disruption in this rhythm can significantly negatively impact many aspects of health, including neurological health. Evidence indicates circadian disruption is a risk factor for neurological disorders.

This article will expand on what circadian rhythm is, the symptoms of circadian rhythm disorder, what causes it, how it affects neurological health, and natural therapies that can help circadian rhythm disorder.


What is Circadian Rhythm?

The circadian rhythm is the body's internal 24-hour clock that syncs up with our daily environmental light and dark cycles. Sleep and wake cycles are an excellent example of circadian rhythm - we are typically awake during daylight hours and sleep during the dark hours of a 24-hour clock.

That said, the body's circadian rhythm is much more than just your sleep and wake cycles. Numerous processes occur in a circadian pattern to keep you healthy. Disruptions in the circadian rhythm often lead to illness and dysfunction in our health.

The release of various neurotransmitters and hormones, such as melatonin, happens in a circadian pattern. In addition to sleep, other behaviors and body functions follow circadian rhythms, such as feeding-fasting cycles, and neurological processes, such as alertness, autonomic nervous system activity (which controls functions like blood pressure and heart rate), and cognitive function.

The circadian rhythm is regulated by a structure in the hypothalamus (an area of the brain that controls many vital body functions) called the suprachiasmatic nucleus (SCN). Light is the primary stimulus feeding this circadian pacemaker. The SCN influences the production of hormones like melatonin and cortisol to regulate the body's sleep-wake cycles.

Melatonin levels rise at night while cortisol levels decrease to signal to the body that it's time to sleep, and cortisol levels rise in the morning while melatonin levels fall to signal that it's time to wake up. Factors that mess with these hormones and the body's circadian patterns not only disrupt sleep and increase the risk for other health problems, such as neurological dysfunction.

The bottom line is that human health and well-being depend on circadian rhythms.

Symptoms of Circadian Rhythm Disorder

Symptoms of circadian rhythm disorders include:

  • Troubles falling asleep, staying asleep, or both
  • Feeling extremely sleepy during the day
  • Extreme fatigue
  • Reduced alertness
  • Troubles concentrating
  • Impaired decision-making and cognitive function
  • Difficulty with coordination
  • Difficulty controlling emotions and mood
  • Headaches
  • Stomach issues

What Causes Circadian Rhythm Disorder?

A misalignment between your sleep-wake cycle and the light-dark cycle of the environment causes circadian rhythm disorders. There are several kinds of circadian rhythm disorders, and various biological and environmental factors can increase the risk for these disorders.

Factors Out Of Your Control

Certain factors are outside your control, such as sex, age, family history, and genetics.

Men are more likely to experience a circadian rhythm disorder associated with going to sleep earlier and waking earlier than desired. Women are more likely to experience circadian rhythm disorders related to hormone changes during certain stages of life, such as pregnancy, childbirth, postpartum, and menopause.

Age impacts the risk for these disorders as well. Teens tend to go to bed later, increasing their risk for a circadian disruption associated with difficulty waking up for school. Sleep and lifestyle habits of older adults similarly put them at risk for circadian rhythm disorders.

Family history or genetic preference for going to bed early or late can increase your risk for circadian rhythm disorders, as can changes in your circadian clock genes.

Occupation or Environment

People who rotate shifts, such as firefighters and police officers, or work late at night are at increased risk for developing circadian rhythm disorders.

People that frequently cross time zones, such as pilots, flight attendants, and people that travel for work, are at increased risk for circadian rhythm disorders.


When lifestyle habits prevent the natural syncing of sleep-wake cycles with light-dark cycles, it can cause an increase in risk for circadian rhythm disorders.

Substances such as alcohol, illegal drugs, and chronic caffeine use increase your risk for these disorders.

Lack of daytime exposure to natural light increases your risk, as does exposure to artificial light at night. Artificial light emits blue light, which the brain perceives as daylight, and prevents the natural nighttime rise in melatonin. Many people habitually use blue-emitting electronic devices late at night, such as smartphones, TVs, and computer screens. These modern-day habits can increase the risk of circadian rhythm disorders.

Unhealthy sleep patterns, such as staying up too late, also increase risk.

When we eat and fast (don't eat) follow a circadian rhythm. Ideally, we eat during the day and fast during the night. When our habits are out of alignment with our circadian rhythm, issues arise. Eating at night contributes to circadian misalignment.

Health Conditions

Many health conditions increase your risk for circadian rhythm disorders. These include genetic conditions affecting melatonin production, such as Smith-Magenis syndrome, and other genetic conditions, including Angelman syndrome and Huntington's disease.

Other conditions that increase the risk for circadian rhythm disorders include conditions that impact eyesight, such as macular degeneration and blindness; conditions that result in brain damage, such as strokes, brain tumors, and traumatic brain injuries; autism spectrum disorders; mental health conditions, including schizophrenia, major depression, bipolar disorder, and obsessive-compulsive disorder; and neurodegenerative disorders, such as dementia, Parkinson's disease, and Alzheimer's disease.

Gut Microbiome

The gut microbiome (which consists of the trillions of microorganisms that live in the gut) plays a prominent role in many aspects of health and appears to impact the circadian rhythm. There is preliminary evidence indicating that dysbiosis, or the disruption in the balance of the gut microbiome, affects sleep loss and results in circadian misalignment.


The stress response is regulated by the HPA (hypothalamic-pituitary-adrenal) axis, a complex hormone communication network between these glands. During the stress response, the primary hormone that is released is cortisol.

Above, we discussed cortisol's role in the circadian rhythm. Cortisol levels drop as we get close to bedtime when melatonin levels rise, and as morning approaches, the opposite signals wakefulness; cortisol levels rise, and melatonin levels decrease.

During periods of chronic stress, the body increases production of cortisol. This increase in cortisol can reduce the production of melatonin, which can impact sleep.

Chronic stress causes alterations in HPA axis activity, which are associated with disruptions in the circadian rhythm.

How Does Circadian Rhythm Affect Neurological Health?

The body's sleep-wake cycle is the most significant output rhythm of the circadian system and significantly impacts neurological health. Impaired sleep-wake cycles are a risk factor for neurological disorders. They precede neurodegenerative diseases by decades and influence their progression.

The most common neurodegenerative condition is Alzheimer's disease, and the second is Parkinson's disease. Both of these conditions exhibit strong circadian rhythm disruptions.

Alzheimer's disease patients exhibit sleep deprivation and poor sleep quality. A hallmark of Alzheimer's disease is a buildup of amyloid-β (Aβ) in the brain. Sleep-wake cycles are shown to influence Aβ: sleep deprivation increases Aβ levels, and people with evidence of Aβ tend to exhibit worse sleep quality and efficiency. Disruption of the sleep-wake cycle is even said to be predictive of dementia.

We've discussed the autonomic nervous system's role in the circadian rhythm. The autonomic nervous system (ANS) controls body functions that are automatic, like blood pressure, heart rate, breathing, digestion, and temperature control. Disruption in the circadian control of the autonomic nervous system is a factor in Parkinson's disease. A reversal of the circadian rhythm of blood pressure is noted in these patients, and a loss of the morning sympathetic peak and circadian heart rate variability (small changes in the time measured between heartbeats, a measurement of autonomic nervous system health).

In addition to circadian disruptions impacting the autonomic nervous system in Parkinson's patients, over 90% suffer from poor sleep and alertness.

Functional Medicine Labs to Test for Root Cause of Circadian Rhythm Disorder

When evaluating the root cause of circadian rhythm disorders, in addition to ordering a sleep study, integrative medicine practitioners order standard comprehensive blood work to assess overall health in addition to functional medicine labs. These functional medicine labs help identify a root cause for the disruption in circadian rhythm.


The DUTCH Plus™ is a urine and saliva test that evaluates the daily rhythm of cortisol, waking levels of melatonin, and the Cortisol Awakening Response (CAR). The CAR is an effective way to evaluate the circadian rhythm as it assesses the morning rise in cortisol that happens when light signals the suprachiasmatic nucleus that daytime is coming. The CAR also provides information about the health of the HPA axis, the stress-response system.

This test also measures markers for neuroinflammation and neurotransmitters, which help determine if circadian disruption impacts the neurologic system.

A marker for dysbiosis is measured to signal whether the gut microbiome may be a root cause of circadian rhythm disorder.  

Vitamin D

Vitamin D is a micronutrient dependent on sunlight exposure. Supplementation with Vitamin D is shown to have a significant impact on sleep, one of the most potent circadian factors. Measuring Vitamin D levels helps individualize a treatment plan for restoring circadian rhythm.


Measuring salivary melatonin levels in the morning, evening, and night offers a one-day snapshot of the sleep-wake cycle.

Comprehensive Stool Analysis

A comprehensive stool analysis assesses the functional health of the gastrointestinal system, measuring markers of digestion, absorption, gut inflammation, immune response, and microbiome health. This test can help identify if gut dysbiosis and inflammation are disrupting the circadian rhythm.


The Doctor's Data NeuroBasic Profile is a urine test that measures neurotransmitters to assess the health of the nervous system. This can be a helpful way to assist in diagnosing neurological conditions and monitor treatment effectiveness.

Complementary and Integrative Medicine Treatment for Circadian Rhythm Disorder

Complementary and integrative medicine treatment for circadian rhythm disorders takes a patient-centered approach. It begins with lifestyle interventions that encourage balance in the circadian rhythm by synchronizing your sleep-wake cycles with the light-dark cycles of the environment.

The most obvious and foundational step is to focus on getting 7-8 hours of sleep, aligning your sleeping hours with darkness and your waking hours with light. There are many integrative treatments known to support better sleep.

Addressing chronic stress is pivotal in restoring quality sleep and promoting circadian health. Mind-body therapies are excellent ways to reduce the impact of stress, promote quality sleep, and support balance in the ANS by stimulating the relaxation response.

Studies show exercise to have a positive effect on both stress and sleep. Moving your body regularly is a great way to support better sleep and encourage circadian rhythm balance.

Nutrition for Circadian Rhythm Disorder

In addition to focusing on nutrient-dense, high-fiber, anti-inflammatory foods that support optimal gut health, a nutritional approach for circadian rhythm disorders addresses food timing.

Time-Restricted Feeding (TRF) is a meal-timing approach where all your daily calories are consumed within a consistent 8 to 12-hour window, optimizing circadian rhythm. Additionally, circadian rhythms are better primed for digestion, absorption, and metabolism of food earlier in the day. This suggests, and the evidence confirms, that it's best to eat larger meals in the first half of the day, smaller meals later in the day, and avoid eating close to bedtime.

Tryptophan is an amino acid that's the precursor to melatonin, so eating foods high in tryptophan provides the required building blocks the body needs to make this hormone. Tryptophan food sources include chicken, turkey, fish, eggs, oats, nuts and seeds, chocolate, and fruits.

Avoiding substances that disrupt the circadian system, such as alcohol and caffeine, is also essential for anyone with circadian disruption.

Supplements and Herbs for Circadian Rhythm Disorder

Integrative medicine practitioners may use various supplements and herbs for circadian rhythm disorders. It's essential to always work with your healthcare practitioner to determine which supplements are right for you. Here are three commonly used supplements to support balance in the circadian system.


Melatonin is the body's "sleep hormone" and a potent antioxidant. Supplementing with melatonin supports jet lag and sleep disorders and realigns the circadian rhythm. Doses between 0.3 mg and 10 mg are often used for sleep disorders; however, it is best to begin with a lower dose and slowly increase as needed. Larger doses, up to 300 mg, have been used to treat some neurodegenerative conditions.

Vitamin D

Vitamin D production within the body depends on exposure to sunlight, so it makes sense that optimizing Vitamin D levels in the body would impact circadian factors such as sleep. A systematic review of the outcomes of Vitamin D supplementation on sleep show Vitamin D supplementation produces significant improvements in sleep quality. The doses used in the studies ranged from 1,000 IU to over 7,000 IU per day; however, dosage should be individualized based on Vitamin D testing.


Adaptogens are herbs that help the body adapt to and regulate stress. These herbs reduce high cortisol levels, support sleep, and support a healthy HPA axis. Schizandra, Rhodiola, and Eleuthero are adaptogenic herbs that support a healthy CAR. Remember, the Cortisol Awakening Response is the morning rise in cortisol and a marker of circadian rhythm health. Ashwagandha is another adaptogenic herb known to have a beneficial effect on cortisol levels.

Light Therapy for Circadian Rhythm Disorder

Light therapy, or bright light therapy, involves using artificial light that mimics daylight and resets your circadian rhythm. Light therapy is performed by sitting in front of a light therapy box to expose the eyes to light. A typical light box intensity for light therapy is 10,000 lux. A typical light therapy session includes sitting with a light box about 16 to 24 inches away from the face for 20 to 40 minutes.

Using a light box when you first wake up can help shift sleep and wake times earlier, and using light therapy in the afternoon or early evening can help shift sleep and wake times to later.

It's important to note that some light boxes used to treat skin disorders do not filter out UV light, so if you're purchasing a light box for light therapy for circadian rhythm disorder, ensure you use a light box that does not emit UV light.

Light therapy is shown to improve sleep, as well as other circadian disruption symptoms, such as fatigue. In people with neurodegenerative conditions, such as Alzheimer's disease, light therapy restores the circadian rhythm timing of sleep and improves sleep quality.

Another important aspect of light therapy is avoiding exposure to bright light, especially in the blue light wavelengths, when it's dark outside. Blue light prevents the nighttime rise in melatonin that naturally occurs when the daylight fades. Avoiding blue-light-emitting devices like TVs, smartphones, and computer or tablet screens is ideal. Many devices have night-shift modes you can set that reduces the amount of blue light the device emits. Another option is to use blue-light-blocking glasses. Studies show these glasses, which typically have amber-colored lenses, prevent the melatonin-suppressing effects of light.


Sleep and circadian rhythms have a strong influence on health and well-being. Disruption in the circadian sleep-wake cycles can damage neurological health and is often predictive of neurodegenerative conditions, preceding them by decades.

Lifestyle interventions such as stress management, exercise, and avoiding eating close to bedtime can be helpful. Therapies such as melatonin supplementation and light therapy are additional ways to restore the circadian rhythm and improve sleep.

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
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