Uncovering more about how Parkinson’s may affect circadian rhythm
Every person has an internal clock known as the circadian rhythm which regulates many essential biological functions throughout the course of the 24-hour day. There is increasing evidence that Parkinson’s disease (PD) can cause disturbances that alter a person’s circadian rhythm and could influence symptoms, treatment response, and possibly even the underlying PD pathology. Understanding circadian rhythm disorders and viewing circadian health as an essential part of Parkinson’s care could offer practical opportunities to improve daily function and quality of life for people living with PD.
What is the Circadian Rhythm?
Many biological processes fluctuate throughout the day on a 24-hour internal clock known as the circadian rhythm. The circadian rhythm is controlled by a group of neurons in the brain called the suprachiasmatic nucleus (SCN), often called “the master clock.”
Body processes that vary based on time of day include:
- Sleep
- Release of hormones
- Body temperature
- Metabolism
- Digestion
- Level of alertness
- Cognitive performance
- Immune function
- and many others
Light exposure is one of the strongest signals that helps to synchronize the internal clock with the environment. Some other cues that maintain a healthy rhythm include regular mealtimes, physical activity, and consistent daily routines.
These systems work together to create a predictable daily pattern, but in PD this timing system may become disrupted for a variety of reasons.
How Parkinson’s Disease Affects the Circadian Rhythm
PD can affect circadian rhythms in two major ways – via alterations in brain chemicals or neurotransmitters, and via alterations in hormone levels.
Dopamine, a key neurotransmitter that is decreased in PD, helps to regulate the circadian rhythm. Other neurotransmitters that regulate the body’s clock and can be altered in PD include serotonin, norepinephrine, acetylcholine, GABA, and glutamate.
In addition, PD can affect the levels of circulating hormones including melatonin and cortisol which also play key roles in the body’s biological clock.
Common Circadian and Sleep Problems in PD
A 2025 study showed that approximately 84% of people with PD had problems with sleep. Several sleep disorders are common in PD including circadian rhythm disorders also known as sleep-wake disorders. These include:
- Insomnia
- REM sleep behavior disorder (RBD)
- Restless legs syndrome
- Excessive daytime sleepiness
- Obstructive sleep apnea
- Sleep-wake disorders
- Delayed Sleep-Wake Phase Disorder (DSWPD) in which a person is not able to fall asleep until the early morning and can’t wake up in the morning.
- Advanced Sleep-Wake Phase Disorder (ASWPD) in which a person falls asleep in the early evening and is awake by the early morning.
These disorders can co-exist or overlap in a person with PD, making it difficult to precisely diagnose and treat what is contributing to poor sleep. It is important to keep in mind that circadian rhythm disorders may play a key role in poor sleep in PD since their treatment is different from other sleep disorders.
Beyond Sleep: Effects of Circadian Rhythms
Circadian rhythms can have an influence on much more than just sleep. They may contribute to other features of PD including:
- Motor symptom fluctuations
- Medication response fluctuations
In addition, these common PD symptoms can be influenced by a disrupted circadian rhythm including:
- Attention/concentration
- Mood
- Depression/anxiety
- Fatigue
Some people with PD may notice that their symptoms vary throughout the day with predictable periods of a particular symptom such as fatigue. Fluctuations are usually attributed to medication dosage or timing, but circadian rhythm alterations can play a role as well. Research is still ongoing to determine if correction of the body’s internal clock can improve overall symptom management.
Finally, key body functions that are involved in PD can be altered by a disrupted circadian rhythm including
- Immune function
- Inflammation
- Digestive health
Research into whether improving circadian rhythm function can have an effect on these and other aspects of health is critical.
Can Circadian Rhythms Influence PD Pathology?
There is evidence to suggest that disrupted circadian rhythms can influence several underlying biological processes involved in PD, including:
- Oxidative stress
- Neuroinflammation
- Mitochondrial function
- Protein clearance
- Cellular repair mechanisms
Additional research is necessary to determine if restoring circadian rhythms can improve the underlying PD pathology and potentially slow PD progression.
Current Research at the Intersection of PD and Circadian Rhythm
Circadian biology has become a very active area of research in PD. Some of the new research is investigating:
- Biomarkers of circadian dysfunction
- Wearable devices/digital health technologies that continuously monitor sleep and activity as well as other daily rhythms
- Melatonin secretion patterns in PD
- Body temperature rhythm patterns in PD
- Circadian gene expression in PD
In addition, a growing field called chronotherapy aims to optimize the timing of treatments to the body’s biological clock. This could include approaches such as bright light therapy, timed exercise programs, scheduled mealtimes, melatonin supplementation, and alterations in medication timing to maximize effectiveness.
APDA has recently funded exciting work into circadian rhythms in PD:
Practical Strategies to Support Healthy Circadian Rhythms
If circadian rhythm disorders are impeding good sleep and affecting other PD symptoms that fluctuate throughout the day, what can be done to correct this?
Evidence-based lifestyle strategies can help support healthy circadian function. Some of these healthy habits to consider incorporating in your daily routine include:
- Maintaining a consistent sleep and wake schedule
- Getting bright natural light exposure shortly after waking up
- Exercising regularly
- Limiting prolonged daytime naps
- Establishing a wind-down routine before bed
Light therapy, involving exposure to specific wavelengths of light, may also have a role in maintaining a health circadian rhythm in PD.
It is always important to discuss these and any other strategies you are considering with your healthcare provider to help establish the best course of action for you. These approaches may not fully eliminate sleep problems, but they can strengthen circadian signals that help to regulate the body’s internal clock.
The Future of PD Treatment
Circadian rhythms can influence most aspects of human physiology, and PD can disrupt this internal clock affecting sleep as well as many other symptoms. Incorporating strategies that optimize circadian rhythms into PD care has the potential of improving a person’s overall quality of life.
Tips & Takeaways
- Circadian rhythms regulate sleep, hormone release, metabolism, and brain function
- PD can disrupt circadian rhythms
- Sleep problems can involve multiple contributing/overlapping issues including circadian rhythm disorders
- Regular light exposure, exercise, and consistent routines help support healthy circadian rhythms
- Research is still ongoing to explore restoration of healthy circadian rhythms and its link to treatment and prevention of PD
- Addressing sleep and circadian health may improve quality of life and symptom management
This blog was written by Clark Jones, PhD, and was reviewed, edited, and approved by Dr. Rebecca Gilbert.