The potential of light therapy for Parkinson’s

Could light hold the key to help manage Parkinson’s symptoms or even have a protective effect on brain cells? This blog explores the research evidence and what the future might hold.

Katherine Fletcher
Jul 8 · 8 min read

Light has a huge impact on life — from sustaining the plants we eat to allowing us to see, everyone of us is dependent on the power of light.

The power of light has been investigated in many conditions, and although it is still very much an experimental technique, there is research to suggest that light therapy can have protective and restorative properties. There is also evidence that light can alter our sleep, mood and behaviour.

So why is light relevant to Parkinson’s?
In Parkinson’s it is the loss of dopamine producing brain cells that cause both movement symptoms and other symptoms — known as non-motor symptoms — such as problems sleeping, depression, and loss of motivation.

Research is being done to look at whether treatment using light could offer protection to struggling brain cells to potentially slow down the progression of Parkinson’s. And research is also looking into how light, in various forms, could be used to directly manage the symptoms of Parkinson’s.

This is a fascinating topic as researchers try to unpick why cells that sit in the middle of the brain, in complete darkness could be protected, or even ‘healed’, by light. How do cells in the eye signal to the deepest parts of the brain? Or is it that light is being absorbed by specific components in cells activating and providing energy for the body to promote brain cell survival, protection or regeneration?

Let’s explore some of the ways light is being looked at with regard to Parkinson’s research.

Natural sunlight

The body makes vitamin D when the skin is exposed to direct sunlight, as well as small amounts being present in certain foods. Vitamin D helps regulate the amount of calcium and phosphate in the body. These nutrients are needed to keep bones, teeth and muscles healthy.

Research has been done looking at vitamin D and Parkinson’s, including research that focuses on exposure to sunlight and how this might be associated with the risk of developing Parkinson’s. This research, alongside other studies looking at supplements for vitamin D, have found that higher vitamin D levels are linked to a lower risk of Parkinson’s.

In addition, studies have indicated that people with Parkinson’s with higher vitamin D levels tend to have better mobility. This research has been done in rats and mice indicating that vitamin D may have protective properties. However, the authors called for more studies in people to confirm these potential benefits.

Bright light therapy

Bright light therapy, as the name suggests, uses a bright lamp to mimic natural light. The intensity of light, the duration and time of day that the therapy administers are all carefully controlled. Bright light therapy is probably most famous for its use in Seasonal Affective disorder (SAD), a form of depression linked to the change in seasons, where decreasing levels of light in the winter months triggers low mood.

But in controlled trials of bright light therapy in SAD, there are mixed conclusions. It seems that it’s down to the individual whether bright light therapy is helpful. There are similar studies and mixed results when looking at bright light therapy and bi-polar disorder. But despite the overall conclusions not being clear cut, one of the more consistent observations, is that bright light therapy can help to improve sleep.

In Parkinson’s trouble sleeping is a common symptom alongside feelings of anxiety, low mood and depression. So, if bright light therapy can potentially improve sleep and other symptoms in other conditions, can it help in Parkinson’s?

There is some evidence in people with Parkinson’s that bright light therapy can improve mood and decrease symptoms associated with depression and anxiety. But like previous studies in other conditions, the evidence is not clear cut. The most recent study in 83 participants with Parkinson's, either receiving a control light or bright light therapy, showed that there was no significant change in overall depression scales. However, mood and sleep improved.

These results are supported in other studies looking particularly at sleep. Bright light therapy seems to help those that struggle to sleep and those that found themselves over-sleeping in the day. This clinical trial was done in 31 people with Parkinson’s receiving bright light therapy, twice a day, for two weeks. These observations suggest benefits of light therapy can happen quickly.

As well as indications that there may be potential for light therapy in managing non-motor symptoms, there is also research to suggest that bright light therapy can potentially improve movement symptoms such as tremor and rigidity. But research is limited in this area and therefore further investigation is needed to assess the impact of bright light therapy on movement symptoms.

There is some evidence that bright light therapy may help struggling brain cells in Parkinson’s. There are theories that light therapy increases dopamine levels in the brain. This could explain why some individuals receiving light therapy are able to reduce their medication. This is supported in rat models in the lab, where dopamine producing cells can respond to light. More research is needed to further explore this — we’ll discuss the power of red-to-near-infrared light as a way to protect brain cells later in the blog.

Evidence so far shows that the effects of bright light therapy on people with Parkinson’s is variable and more large scale trials are needed to assess the long term benefits. The research so far has used different methods such as ‘doses’ and duration of light therapy, therefore, finding a consistent method would be useful for future research. On the other hand, it could be argued that light therapy needs to be tailored to the individual to have the best results. And unfortunately, there has been little research done into understanding why bright light therapy may be having an impact in Parkinson’s.

Near-infrared light therapy

There are many names for near-infrared light therapy — Low-level laser therapy (LLLT) or photobiomodulation to name a couple — this blog is going to use the term near-infrared light therapy.

Light has different wavelengths. When light falls within what is known as the visible spectrum, the wavelength impacts the colour we see the light. The spectrum of visible light goes from the near-infrared range with long wavelengths, to the other end, where you find ultraviolet light with short wavelengths. Near-infrared light therapy uses light that has a relatively long wavelength, between 600–1070 nm. In comparison bright light therapy uses light from the 460–525 nm region of the spectrum.

Flickr image

Different parts of our cells can absorb different wavelengths of light. The longer wavelengths, like the red to near-infrared end of the spectrum, are thought to be better absorbed by specific components within the cell such as those that help control the cell’s energy levels. There is increasing evidence in many different conditions that near-infrared light therapy has protective properties and restorative properties.

So, is there evidence that near-infrared light therapy is protecting brain cells in Parkinson’s? The answer is yes, but it comes mainly from research in the lab in cell-based and animal models of Parkinson’s. Nevertheless, the results look promising, where near-infrared light therapy decreases stress in brain cells, protects dopamine producing cells and shows improvement to movement symptoms.

The knowledge so far suggests near-infrared light therapy is more beneficial when applied directly or in close proximity to target cells. This poses a problem in Parkinson’s as the cells implicated in the condition sit deep in the mid brain. To get round this, some researchers suggest using an optic fibre device, that can be surgically inserted into the brain, would have the most potential to directly impact cells in Parkinson’s.

There is a particularly interesting research study in animal models that uses the optic fibre device to look at near-infrared light therapy in Parkinson’s. The therapy was shown to be beneficial to the mice, rats and monkeys and interestingly shows a potential link between light therapy and an increase in a growth factor in the brain called GDNF. This is particularly topical as a recent clinical trial of GDNF showed that directly infusing the growth factor into a specific area of the brain in people with Parkinson’s could have protective and regenerative effects on dopamine-producing brain cells. Therefore, could light therapy offer an alternative way to boost GDNF in the brain and protect brain cells? It will be interesting to see further research on this topic.

There has been limited investigations of near-infrared light therapy in clinical trials in people with Parkinson's. One study, in 8 people with Parkinson’s, showed that near-infrared light therapy after 2 weeks may improve speech, cognition and freezing when used as a non-invasive therapy, so using the light source outside of the body. But larger trials are needed. In addition, results from a study of 36 people with Parkinson’s found that an intranasal device led to an improvement of Parkinson’s symptoms over a course of 10 days. There is a larger trial in the US about to start looking at 135 people with Parkinson’s using intranasal near-infrared light therapy. It will be interesting to see the results from this larger trial.

There is also news of ‘red light helmets’ being investigated in Tasmania and Australia. These helmets were inspired by research done in mice, where near-infrared light therapy was administered via helmet like devices and shown to improve the Parkinson's-like symptoms. The news relates to an imminent clinical trial wanting to test these red light helmets in people with Parkinson's. There are no details, as of yet, about this trial but this is something we will keep an eye on to see how it progresses.

Should people try near-infrared light therapy?
Although light therapy is thought to be safe with minimal side effects, we don’t advise people seek out this therapy as a treatment for Parkinson’s. There needs to be more research into the long term impact of near-infrared light therapy and the benefits to people with Parkinson's. The research so far has used various techniques and each needs to be investigated in larger, longer, controlled clinical trials. Any changes in managing Parkinson's should be discussed with a medical professional.

Parkinson’s UK

Get the latest research news, discover more about Parkinson’s and read about how others are getting involved. For information and support, visit www.parkinsons.org.uk

Katherine Fletcher

Written by

Research Communications Officer

Parkinson’s UK

Get the latest research news, discover more about Parkinson’s and read about how others are getting involved. For information and support, visit www.parkinsons.org.uk

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