Luminotherapy and health: cancer, acne, sleep, how to do it?

Light therapy is therapy using light. It has proven its effectiveness in treating depressive episodes, sleep/wake rhythm disorders, and other indications are being studied. List of health benefits with Pr Patrice Bourgin, neurologist.

Definition: what is light therapy?

Light therapy, which is part of phototherapy (light therapy), is a treatment consisting of the daily exposure of a person's eyes to an artificial light source devoid of infrared (IR) and ultraviolet (UV) light using lamps. "Light therapy refers to the effects of light" informs Professor Patrice Bourgin, neurologist and head of the sleep disorders center at the University Hospital of Strasbourg and a CNRS research team at the Institute of Neurosciences in Strasbourg. Light has indirect and direct effects on our organism. "It has indirect effects on our biological clock and on the regulation of sleep/wake rhythms and direct effects on a large number of physiological and behavioral parameters, such as heart rate or mood and attention: the Anglo-Saxons use the term "alertness", which can be translated as vigilance, performance of wakefulness. Light has beneficial effects on cognition, on working memory. Light also acts at night by suppressing the production of melatonin which is a hormone synthesized at night and allows us to synchronize our sleep-wake rhythm and our biological rhythms". Note: light therapy is not reimbursed by Social Security.

What are the health benefits of light therapy?

"Light has effects on physiology and mental health" teaches Professor Patrice Bourgin. "Its effects depend on the intensity of the light, the time of exposure, the duration of the latter and the spectrum of light (wavelengths)" details Professor Bourgin. Wavelength is measured in nanometers. "The most established medical indications for light therapy are depression, in particular that accompanied by phase delay, circadian rhythm disorders, insomnia, neurodegenerative diseases such as Alzheimer's and Parkinson's, with interest in the context of comorbidities (depressive element of these diseases, sleep disorders" informs Professor Bourgin. Light therapy is done with validated home light therapy lamps. A standard treatment regimen is to expose yourself daily to 10,000 Lux for 30 minutes or 5000 lux for one hour. "Today there are light therapy glasses that have the advantage of being able to be used on an outpatient basis in everyday life" says Professor Bourgin. "Other medical indications for light therapy are being developed. 'assessment', he specifies. The effects of light are also used to treat certain dermatological diseases (acne, psoriasis, etc.): this is referred to as phototherapy.

What are the benefits of light therapy against cancer?

The benefits of light therapy in the context of cancer are not yet validated by scientific evidence. There is research in particular on the interest of luminotherapy in the management of persistent fatigue in people who have been treated by cancer and on the management of depressive symptoms in the context of cancers. Dynamic phototherapy (PDT) is offered as a treatment for certain cancers (in particular superficial skin cancers).Dynamic phototherapy is a treatment based on the interaction between a photosensitizer and a light source of wavelength adapted to the absorption spectrum of the photosensitizer. This interaction, in the presence of oxygen, leads to the formation of free radicals allowing the destruction of the lesions.

What are the benefits of light therapy for acne?

Dynamic phototherapy and exposure to blue light could be treatments for treatment-resistant acne. However, the effectiveness of dynamic phototherapy and blue light treatments for acne has not been validated.

What are the benefits of light therapy for joint pain?

Infrared phototherapy could help relieve joint pain, including that of osteoarthritis. The effects of light therapy on joint pain are being evaluated. "Light therapy has proven its effectiveness in relieving non-motor disorders of Parkinson's disease and symptoms of Alzheimer's disease" says Professor Bourgin.

What are the benefits of light therapy for depression?

One of the recognized indications for light therapy is the management of depressive episodes. "Our team published after meta-analysis (composition and synthesis of studies) a study concluding that light therapy was as effective as reference anti-depressants and that the combination of light therapy and anti-depressants was more effective than anti-depressants alone or light therapy alone" tells us the neurologist, whose team would like light therapy to become a first-line treatment for depression in the same way as antidepressants. "Light therapy does not have the side effects of anti-depressants" emphasizes Professor Bourgin. Light therapy seems particularly indicated in depression with phase delay (people who go to bed very late and get up very late). "Work on a larger scale is underway to clarify which modes of administration of light therapy are most suitable for depression and for which types of patients" announces the neurologist.

What are the benefits of light therapy for psoriasis?

Two types of phototherapy are used in the management of severe psoriasis: UVB phototherapy and PUVAtherapy. UVB phototherapy is a treatment consisting of irradiating the body with ultraviolet B (UVB) rays without taking photosensitizing medication. PUVAtherapy is a treatment that consists of irradiating the body with ultraviolet A (UVA) rays after taking a photosensitizing drug. It is the anti-proliferative effect and the immunomodulatory effect of UV exposure that explains the beneficial effects on psoriasis.

What are the benefits of light therapy for sleep?

Light therapy has benefits in the management of circadian disorders (wakefulness/sleep disorders: phase advance (sleep occurs early in the evening with an early awakening in the night) and phase delay (sleep occurs late and awakening is late). "Important studies are underway on light therapy and insomnia" teaches Professor Bourgin. "A meta-analysis already makes it possible to see a beneficial effect of light therapy on insomnia, which depends on the intensity of the light and the mode of administration" he analyzes.

What are the dangers and side effects of light therapy?

Light therapy presents little or no danger, it will be avoided in the event of significant retinal damage. On the other hand, there may be some side effects, mainly related to an unsuitable mode of administration. “Light therapy done at inappropriate times can aggravate the symptoms instead of improving them” warns Professor Bourgin.

For example, in sleep disorders, if light therapy is done too late at night, it can lead to insomnia, hyperactivity, if done in the morning too early it can cause early awakening, no falling back to sleep). Light therapy can be accompanied during the first days by nausea, headache, irritability. If these effects persist for more than a few days, the dose of light therapy should be reduced. Finally, "You should know that it is a really active treatment in depression, like anti-depressants. Also, there is a risk, albeit rare, of manic access in a person suffering from bipolar disorder" informs the neurologist.

What precautions to take?

"It is better to have a medical supervision to do light therapy" warns Professor Bourgin. "This must be done at specific times depending on the indication: for example if we use light therapy early in the morning we advance the circadian rhythm, if it is used in the evening it delays the circadian rhythm" he describes. Also, it is better to go through sleep centers or psychiatrists who are interested in light therapy. “In the event of extreme circadian rhythm disorders, an expert must calculate the appropriate exposure times” indicates the specialist.

What are the contraindications of light therapy?

There are few contraindications to light therapy. Severe retinopathy is one of them. "When the retina is damaged, it is recommended not to expose yourself too much to light" explains Professor Bourgin. It is recommended for people with cataracts, AMD, glaucoma to take the advice of the ophthalmologist before having light therapy sessions.

Thank you to Pr Patrice Bourgin, neurologist and medical director of the sleep disorders center and the international center for research in ChronoSomnology (CIRCSom) at the University Hospital of Strasbourg as well as a CNRS team at the Institute of Neurosciences of Strasbourg ( INCI team 9 of UPR 3212).)

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