The connection between sleep and Parkinson's disease

Parkinson’s disease is commonly associated with shaking and slow movement, but these symptoms are only the tip of the iceberg. For some patients, a disrupted sleep schedule is their primary and most life-affecting symptom. It’s estimated that sleep disturbances affect more than three-quarters of people with Parkinson’s. For some, sleep disorders began decades before the diagnosis of Parkinson’s, which inevitably raises the chicken or egg question. What comes first – Parkinson's or poor sleep?

The relationship between sleep and Parkinson’s is complex, but irrespective of cause and/or effect, the circadian clock can explain many of the underlying mechanisms of the disease.

We recently turned back the clock an hour, and many might have taken a few days to adjust their circadian clock to their daily routines. The circadian rhythms are the physical, mental, and behavioural changes that follow a 24-hour cycle, regulated by circadian clock genes, known as CLOCK and BMAL1 genes.

The master pacemaker – found in a tiny region in the brain that responds to light changes in our environment – sends signals to the cells in our body, synchronising organs and tissues with the sleep-wake cycle. There is evidence that circadian rhythm disruption is an environmental risk factor for Parkinson’s.

A diagnosis of Parkinson’s is often preceded by what is known as Rapid Eye Movement (REM) sleep disorder, a condition in which people physically and vocally act out their dreams and don’t have the normal muscle paralysis that should occur during REM sleep.

REM sleep disorder disrupts the rhythmic secretion of the protein BMAL1 which in turn disrupts the secretion of many other essential proteins that depend on the expression of BMAL1, which disrupts the normal circadian cycle.

How decreases in BMAL1 levels and a disrupted circadian cycle may lead to Parkinson’s is still unclear. We know that reducing BMAL1 expression in mice increases inflammation, contributing to faster disease progression. Exposing otherwise healthy mice to circadian disruption, such as longer hours of bright light or complete darkness, worsens motor symptoms and increases dopamine loss and inflammation.

Light is the primary stimulus that controls our circadian rhythms, entering the retina and reaching the master pacemaker clock, aligning it with the outside world. Parkinson’s patients often have reduced sharpness in vision, which may be because of loss of retinal cells, lack of dopamine, or simply because Parkinson’s patients might spend less time outside and exposed to natural light, which affects the body’s internal clock aligning with day and night.

An additional cause is the clumping of alpha-synuclein proteins in the brain. The clumps of this neuronal protein accumulate in the brain of people with Parkinson’s. These clumps interfere with the release of neurotransmitters and impair signals sent to pacemakers in organs and tissues, interfering with sleep. Disrupted sleep reduces the brain’s ability to remove these clumps, worsening things and accelerating the process.

The connection between Parkinson’s and sleep is complicated, and there is much yet to untangle and understand, including if Parkinson’s and circadian rhythm influence one another in a negative – or positive – feedback loop. Irrespective, it is clear that sleep should be considered a key health priority in reducing the risk of developing Parkinson’s disease and slowing disease progression for those with it.

What can you do?

Prioritise your sleep routine

Our circadian rhythm allows us to feel natural tiredness during certain hours: 1pm-3pm and 2am-4am. The more we align our rest with the natural hours of tiredness, the better our sleep quality.

Furthermore, going to bed and waking at the same time every day allows your brain to adapt to this schedule, making falling asleep easier. Naps can play a part in a healthy sleep routine.

Generally, adults' best nap length is about 20 minutes and no longer than 30 minutes. Sleeping for 20 minutes provides the benefits of light sleep without entering into a deep sleep, which can cause grogginess and worsen sleepiness. Longer naps (about 90 minutes) can benefit shift workers trying to avoid fatigue. This time allows the body to cycle through the stages of sleep and avoids interrupting deep sleep.

Consider how your work life is affecting your sleep

Working irregular shifts and going to bed at different times every night causes your circadian rhythm to become off-balance, which will need help to adapt to natural hours of day and night. Taking melatonin supplements could help regulate your sleep-wake cycle. More importantly, consider how this job's lifestyle may affect you in the long run.

Talk to a doctor about medication

Some studies have found medication used to treat Parkinson’s, such as Levodopa, may cause sleep disruption. These studies found increased excessive daytime sleepiness and increased nocturnal activity. Dopaminergic medicines can interfere with the secretion of melatonin. Therefore, the timing of taking such medication may need to be adjusted and can be potentially coordinated with melatonin supplements to improve one’s sleep schedule.

Exercise

Physical exercise may affect circadian melatonin secretion differently depending on when you exercise. Evening exercise can offset the nocturnal melatonin rise and increase the fight-or-flight response during the evening. Morning exercise, however, may enhance the rest-and-relax response, allowing for increased daytime wakefulness and night-time sleepiness.

Reduce calorie intake before sleeping

The circadian rhythm primarily relies on sunlight to regulate these functions, but food is a powerful secondary circadian time cue. Set mealtimes help reinforce the natural circadian rhythms. People who practise intermittent fasting also have higher levels of human growth hormone, with effects seen after a few weeks. While we sleep, this hormone burns fat, restores muscles, and helps the body repair itself at a cellular level. As a result, people who fast wake up feeling more refreshed and restored after sleeping.

Sleep plays a vital role in good health and wellbeing throughout life and might be the single most crucial aspect of a healthy lifestyle to protect us from a myriad of diseases and help us manage those we are affected by.

A good night's sleep is not for the weak but for those who want to live their best lives.