Natural light: a fundamental regulator of the human body
Even before addressing Parkinson’s disease, it’s essential to recall the vital role natural light plays for the entire population.
Each morning, exposure to daylight resets our internal biological clock (also known as the circadian rhythm). It synchronizes our sleep cycles, boosts alertness, improves mood, promotes serotonin production, and regulates melatonin secretion in the evening. It also supports the synthesis of vitamin D, essential for our bones, immunity, and brain function.
Several studies have shown that a lack of natural light is linked to increased mood disorders, sleep issues, metabolic problems, and cognitive decline—even in healthy individuals.
The harmful effects of artificial light
On the flip side, not all sources of light are equal. Excessive exposure to artificial light—especially in the evening—disrupts our biological rhythms. It desynchronizes our internal clock and can lead to sleep disturbances, chronic fatigue, and even impaired brain plasticity.
In a comprehensive review published in Brain Research Bulletin, researchers emphasized that certain types of artificial light, such as neon lights or LED screens, can trigger oxidative stress in the brain and disrupt dopamine regulation. In rodents exposed to prolonged artificial light conditions, researchers observed a loss of up to 30% of dopaminergic neurons in the substantia nigra—a key region in Parkinson’s pathology.
Moreover, excessive exposure to artificial light reduces melatonin secretion, which is highly problematic. Beyond its well-known role in sleep regulation, melatonin also has antioxidant and anti-inflammatory properties that are particularly important for people with Parkinson’s disease.
Since oxidative stress and chronic inflammation are two key mechanisms in the progression of the disease, several studies have explored melatonin’s neuroprotective potential. One study published in Neurobiology of Aging, using an animal model, revealed that higher levels of melatonin can reduce oxidative damage in the substantia nigra and protect dopaminergic cells.
Daylight exposure and Parkinson’s prevention
What if daily exposure to natural light played a preventive role against certain neurodegenerative diseases?
This is precisely what a large cohort study conducted with more than 375,000 UK Biobank participants suggests. Researchers found that individuals who spent more than 2 to 3 hours per day outdoors—especially in winter—had a significantly reduced risk of developing Parkinson’s disease. Each additional hour spent outside was associated with a 4–6% decrease in risk.
Remarkably, this was independent of genetic risk factors. Indeed, the benefits of sunlight exposure were consistent regardless of an individual’s genetic predisposition to Parkinson’s disease. This means that sunlight exposure is a significant preventive lever against neuronal degeneration—accessible to everyone, even those at high risk.
Furthermore, a meta-analysis published in Medical Science Monitor confirms that even just 15 minutes of weekly exposure to sunlight is associated with a drastic reduction in Parkinson’s risk. These benefits may be partly explained by the activation of vitamin D synthesis, which appears to play a preventive—if not therapeutic—role in protecting neurons.
Lastly, a study titled “Vitamin D and sun exposure in newly diagnosed Parkinson’s disease” compared recently diagnosed patients to healthy individuals of the same age. The result: those with the highest sun exposure levels (more than 12 hours per week) had about 50% less risk of being affected by the disease.
Light and dopamine: measurable effects in the early stages of the disease
In the early years following a Parkinson’s diagnosis, light exposure also appears to regulate several key biological systems—especially dopamine, vitamin D, and sleep-wake rhythms.
A study published in Nutrients (2016) showed that natural light is the primary pathway for activating vitamin D, far more effective than diet, and that this vitamin is frequently deficient in people with Parkinson’s disease. The study demonstrated a strong correlation between natural light and dopaminergic activity, reinforcing the idea that light exposure is not merely a comfort measure, but an active biological factor capable of supporting neural circuits early on in the disease.
In parallel, a brain imaging study published in Movement Disorders (Booij et al., 2023) revealed that in early-stage Parkinson’s patients, dopamine transporter (DAT) availability significantly varied based on sunlight exposure. Patients examined in spring or summer showed higher DAT levels than those examined in autumn or winter.
In other words, the more natural light exposure, the more supported dopaminergic activity seems to be. These results suggest that natural light could help sustain dopamine activity as early as the first stages of the disease.
A more recent study, the PHASE study (Obayashi et al., Sleep, 2024), supports these findings by analyzing actual light exposure in nearly 200 patients with Parkinson’s compared to more than 1,000 healthy controls. Researchers found that people with Parkinson’s were exposed to less light during the day and more artificial light at night, particularly in the later stages of the disease.
This study indicates that circadian rhythm disturbances in Parkinson’s are not merely a side effect of the disease. It’s increasingly recognized that restless sleep often precedes Parkinson’s and may be linked to a lack of natural light exposure, excessive artificial light, and disrupted sleep.
Correcting this environment becomes an accessible strategy—one that can improve sleep, alertness, cognition, and indirectly, quality of life.
The benefits of light for people with Parkinson’s: a promising therapeutic approach
For people already diagnosed with Parkinson’s, the data on light therapy (also known as phototherapy) is becoming increasingly compelling.
A recent meta-analysis (Medical Science Monitor, 2022) compiling five clinical trials showed that light therapy:
significantly improves motor symptoms (UPDRS III score),
reduces depression symptoms,
and enhances sleep quality, with no serious side effects reported—except for minor headaches or temporary eye discomfort in some cases.
The best results are achieved using polychromatic white light, applied in the morning and late afternoon, in 30-minute sessions over several months.
Contrary to popular belief, longer exposure doesn’t yield better results: it’s regularity and proper dosage that make the difference.
In this context, it’s worth noting that sunlight also emits white light with a polychromatic spectrum (i.e., it includes the full range of colors), so sunlight exposure is in itself a form of light therapy.
Infrared light: beyond circadian rhythms, toward neuroprotection
Finally, near-infrared light, through a field known as photobiomodulation, is attracting growing attention from researchers due to its neuroprotective effects.
According to a review published in Neural Regeneration Research, this type of light penetrates deeply into tissues and stimulates mitochondrial activity, improves cerebral blood circulation, and increases the production of neural growth factors such as BDNF and GDNF, both of which are essential for the survival and proliferation of dopaminergic neurons.
In animal studies, results are promising: experiments show reduced dopaminergic degeneration as well as partial restoration of motor functions.
Remarkably, these beneficial effects are observed even when the light is applied far from the brain, such as to the neck or abdomen. This suggests a systemic effect, possibly mediated by the immune or vascular systems.
Although photobiomodulation is still experimental in humans in the context of Parkinson’s, these preclinical findings open the door to an innovative, non-invasive approach that aims to slow neurodegeneration, rather than merely compensate for its symptoms.
Additionally, preliminary clinical trials reported in a review published in the Journal of Personalized Medicine have shown significant improvements in both motor and non-motor symptoms—including walking, balance, sleep, and cognition—without notable side effects. Some participants maintained these benefits for up to a year, and the treatments can even be carried out at home using LED helmets.
In conclusion: Reintegrating light as an ally for our health
This is not to claim that light is a miracle cure for Parkinson’s. But the data is converging: sufficient exposure to natural light has multi-level benefits, whether we are healthy, recently diagnosed, or already undergoing treatment.
Where traditional Parkinson’s management sometimes struggles to offer simple solutions, light becomes a fundamental environmental health lever—free and accessible to all—provided it is used wisely: daylight yes, light pollution no; natural rhythms yes, nighttime screens no.
It is therefore essential to step outside: take walks, garden, sit in the sun on a balcony, or engage in any activity in natural light. Especially in summer, it’s best to avoid prolonged UV exposure and favor the gentle hours of morning or late afternoon.
Reintegrating light into our prevention and care strategies means recognizing the power of life and nature.
A short walk—or even sitting on a sunny bench—can already be a powerful way to feel better.
Reconnecting with sunlight, as simple as it may seem, might already be an essential step toward self-care.
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This blog is not intended to provide medical advice. If you have medical questions, please consult your healthcare professional.