Parkinson's & the Circadian Role of Melatonin

It’s the time of year when we begin to feel some distinction in our bodies that relate to the change in light.

Our body clocks, more formally known as our circadian rhythms, take their cues from the light-dark cycles of the natural world around us.

With longer nights and shorter days, our bodies may tend to want to sleep more. We may have less energy during the day. Our appetites may change, as well as our desire to exercise. It doesn’t help when the weather grows cooler or stormier. Our moods, too, can change as a result of less natural light.

For people with Parkinson’s disease (PD), these changes to the body clock may be even more pronounced, especially in older people.¹

What can a person with PD do to maintain healthy circadian rhythms?

Circadian rhythm basics

Our bodies maintain a sense of time according to the changing of seasons that accompany the light-dark cycles of the planet. This has a direct influence on daily activities, especially processes like sleeping and eating.

Natural light delivers signals to the brain through the optic nerve which have a big impact on our sleep-wake cycles in particular. We take our “time cues” by the light we see. If we experience bright light, this tells our brain to release hormones to help us maintain alertness, wakefulness, and energy.

As the light dims later in the day, our brain takes this as a cue to release the “sleep hormone,” melatonin, in a slow progression toward relaxation and, eventually, sleep.

Melatonin and the circadian system

Disruptions to our circadian rhythms can leave us feeling fatigued, irritable, and “out of sorts.” If you’ve experienced jet lag, you know the feeling. Fortunately, it passes once you adjust.

This adjustment occurs, in part, due to adaptations by the pineal gland in the brain, which releases the hormone melatonin. Melatonin may be best known for regulating sleep, but it plays a larger role in overall health.

It works across body systems to support major functions. For instance, melatonin provides guidance in the timing of digestion.

Melatonin, then, is a workhorse for the circadian system. For this reason, researchers always look at its levels to uncover clues to disruptions of the body clock.

Circadian rhythm disruption

Unfortunately, in the case of PD, a disturbed circadian system leads to its more common nonmotor symptoms. Research even suggests that a chronically disrupted body clock may precede the onset of PD by years and could contribute to PD-related neurodegeneration itself.²

Which nonmotor symptoms of PD are most linked to circadian dysfunction? Recent research published in Frontiers in Neuroscience suggests three big concerns:³

• Sleep disorders
• Gastrointestinal dysfunction
• Cardiovascular symptoms

Melatonin levels in people with PD

The researchers studied early-morning levels of melatonin found in the plasma of people with PD. They found their levels to be significantly higher than in people without PD. Melatonin levels should increase at the end of the day and into the night, and fall in the morning.

While they’re still puzzling out why this happens, they have theories:

• Melatonin may serve an important neuroprotective role they don’t currently understand
• Elevated levels of melatonin in the morning may simply mark the circadian system’s effort to compensate for the neurodegeneration related to PD

Another theory? Most people with PD live with chronic circadian disruption. These elevated melatonin levels provide ongoing evidence.

People with PD struggle with disrupted sleep

The study’s findings matter in one specific way for people with PD. Of the many roles the circadian system plays in human health, its most recognized is sleep regulation.

People with PD struggle with disrupted sleep. These disruptions can include insomnia, excessive daytime sleepiness, fragmented sleep patterns, and inadequate sleep.

Meanwhile, when people with PD do achieve a good night of sleep, they tend to report improvements in their daytime symptoms.

Medical specialists can help prioritize sleep

If you have PD, you likely have a complicated relationship with melatonin and should probably avoid taking this over-the-counter therapy if you can’t sleep at night.

Instead, if you struggle to get good quality sleep or encounter periods of intense sleepiness during the day, it’s a good idea to talk about these problems with your specialist. They can help you find better sleep through medications or non-drug alternatives. Suggestions for improved sleep hygiene also support easy, low-cost ways to prioritize sleep.

Finally, they might refer you to the services of a CBT-i practitioner.⁴ This medical professional specializes in cognitive behavioral therapy for insomnia. CBT-i can help people with PD learn ways to “reset” their circadian systems to make way for more and better sleep.⁵

The therapy is widely available in telehealth applications which allow you to safely participate from the comfort of your own home.