Bright Side of Blue Light

Introduction 

With the emerging presence of technology, increased contact with electronic devices has given rise to problems regarding prolonged exposure to blue light, including interruption of the circadian cycle, damage to retinal cells, and other vision-related issues [1]. Despite the aversive side effects of blue light, it holds therapeutic promise for a variety of different conditions. Phototherapy, in the form of UV light, is mainly used to treat skin conditions [2]. Recently, researchers have started investigating other applications of phototherapy, including blue light therapy. Blue light therapy is being explored as a potential therapy for traumatic brain injuries, which result from violent blows or jolts to the head that can be debilitating or even fatal [3]. Currently, there are a limited number of treatment options for traumatic brain injuries. Yet, blue light therapy has shown to facilitate structural and functional recovery and improve various executive functions such as memory, alertness, and attention in the treatment of mild traumatic brain injuries [4]. 

What is blue light? 

Smartphones, computers, and tablets are just a few of the devices we interact with on a day-to-day basis that emit what we know as blue light. Blue light is part of the visible light spectrum, a range of wavelengths that the human eye can detect, and it resides within the range of 380 to 495 nanometers [5]. Blue light is hazardous due to its shorter wavelength, which is associated with high photon energy [6]. Over time, blue light can damage retinal cells and cause macular degeneration [1]. Macular degeneration, usually associated with aging, is when the macula - a region of the retina that controls sharp, straight-ahead vision - becomes damaged and results in blurred vision [7]. Despite this potential hazard, blue light has been investigated regarding its impact on attention, cognition, and therapeutic potential for related conditions. Some studies have shown evidence that blue light administration has been effective in maintaining daytime arousal and minimizing fatigue; others have demonstrated the increased activation of certain areas of the brain that are involved in cognition and task-related brain regions [8].

Phototherapy 

One form of phototherapy consists of a controlled administration of non-ionizing radiation from the ultraviolet part of the electromagnetic spectrum [9]. Phototherapy has a diverse range of applications but is mainly used for skin conditions such as psoriasis, eczema, atopic dermatitis, and vitiligo [9]. In order to treat skin conditions, these light spectrums are produced artificially and administered via a cabinet with the patient inside [9]. Different types of ultraviolet spectrums, such as ultraviolet A-1 (UVA-1) or ultraviolet B (UVB), can be used depending on the disorder or condition being treated. UVA-1 has a longer wavelength, and UVB has a shorter wavelength, which differentiates its applications [10]. UVA-1 therapy possesses advantageous abilities including penetrating into the deep layers of the skin and activating apoptotic pathways within malignant T-cells, leading to cell death [11]. When functioning normally, T-cells work with our immune system to maintain health and prevent disease. However, when they become abnormal, they can initiate and promote the pathogenesis of autoimmune diseases [12]. UVB has unique properties including anti-inflammation and immunosuppression, but can have negative impacts due to its cytotoxic properties [9]. Cytotoxic agents are used to kill cancer cells by preventing them from dividing and growing, but they can also cause the destruction of healthy, normal cells [13, 14].

Blue Light Therapy: A Treatment for Mild Traumatic Brain Injuries 

It is estimated that 2.5 million people sustain a traumatic brain injury (TBI) annually, but, despite its prevalence and major contribution to death and disability, it is still challenging to treat because of its physiological and diagnostic complexity [15, 16]. TBI can be caused by forceful bumps, blows, or jolts to the head, and in other cases, by an object piercing through the skull and into the brain [17]. TBI can range from mild to severe depending on the size, severity, and location of the injury, and these factors all impact recovery. They can interrupt behavioral and cognitive functions including how individuals understand, move, communicate, and act. More severe cases can lead to permanent brain damage, disability, and death [17]. TBI’s physical, cognitive, and behavioral outcomes range from headaches and seizures to vision impairments and nausea. Additionally, they can be followed by cognitive and behavioral changes such as problems in memory, concentration, decision-making, sleep patterns, and irritability [17]. Brain damage following a TBI can be temporary or permanent, and recovery can be prolonged depending on the injury itself, genetics, and age of the individual facing the TBI [17]. 

In severe TBI, there is an immediate need for medical care in order to prevent secondary damage. This entails monitoring blood flow to the brain, brain temperature, cranial pressure, and oxygen supply [17]. Individuals who experience mild traumatic brain injuries (mTBI) are often recommended to rest and use over-the-counter pain relievers while being monitored to observe any progression of the injury [17]. However, TBI induces structural and pathophysiological changes, including axonal injury, which may lead to pathophysiological changes that can present, for example, as working memory deficits [18].

One study highlights the potential of blue light therapy in treating mTBIs. In this study, 28 individuals who met the criteria for mTBI underwent six weeks of daily morning light therapy with either blue light or a placebo of amber light [4]. These sessions consisted of 30 minutes of light administration within the first two hours of waking up. Researchers observed white matter tracts of the brain throughout 11 regions. White matter tracts play an important role in the connectivity of the brain between different cortical regions by facilitating circuitry in sensory functions, intellect, and emotion [19]. mTBIs are associated with microscopic changes in white matter axonal tracts and fractional anisotropy, and particularly the movement and speed of water moving along fiber tracts [4]. Researchers found that blue light therapy can affect the recovery of brain structures and function following mTBI, including the increase in memory and sleep latency scores, which are promoted by normalized values of water diffusion following blue light therapy [4]. Individuals who were recovering from an mTBI had their sleep assessed by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) which measures different types of memory including delayed memory, immediate memory, attention and language abilities [4]. Additionally, to measure the diffusion properties of white matter tracts, diffusion-weighted imaging (DWI) was performed [4]. White matter integrity (WMI) was also measured, and it was found that individuals who received the blue light therapy had greater WMI in the right thalamus and bilateral prefrontal and orbitofrontal cortices [4]. By measuring daytime sleepiness before and after treatment, researchers found an overall improved daytime sleepiness rating, which was associated with greater WMI in patients who underwent blue light administration [4]. It was concluded that blue light therapy increased WMI and functional connectivity in areas that are involved in sleep regulation, daytime cognitive function, alertness, and attention [4]. 

Fatigue has been reported following TBI, yet treatment for this particular symptom has not been established. To investigate how blue light therapy can improve fatigue in patients with TBI, researchers had patients undergo blue light therapy for 45 minutes per day over a period of four weeks [20]. Similar to the trends of the previously mentioned studies, they found that blue light therapy indeed reduced fatigue and daytime sleepiness during the treatment phase in comparison to control groups [20]. Blue light therapy has demonstrated promise in alleviating multiple areas that are affected in mTBI, which emphasizes its potential as a treatment for this condition. .

A Bright Future for Blue Light 

Blue light therapy has shown promising results in the recovery of traumatic brain injuriesby improving memory, sleep, attention, and fatigue, all of which are essential functions for our daily lives. In addition to mTBI treatment, blue light therapy is being investigated in the context of improving concussion symptoms [21]. With future research, there is potential for blue light therapy to gain approval as a treatment for these brain injuries, which will enhance research in future applications where treatment options are limited.

References

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2. Phototherapy (Light Therapy). (2022, October 22). Cleveland Clinic. https://www.google.com/url?q=https://my.clevelandclinic.org/health/treatments/24385-phototherapy-light-therapy&sa=D&source=docs&ust=1708059855975397&usg=AOvVaw1sr4mwvmkvbQZ0KAepTTzE 

3. Mayo Clinic Staff. (2021, February 4). Traumatic brain injury. Mayo Clinic. https://www.google.com/url?q=https://www.mayoclinic.org/diseases-conditions/traumatic-brain-injury/symptoms-causes/syc-20378557&sa=D&source=docs&ust=1708059855976082&usg=AOvVaw0xhF2bmudOcihdsIOMpmKZ

4. Bajaj, S., Vanuk, J. R., Smith, R., Dailey, N. S., & Killgore, W. D. S. (2017). Blue-Light Therapy following Mild Traumatic Brain Injury: Effects on White Matter Water Diffusion in the Brain. Frontiers in Neurology, 8. https://doi.org/10.3389/fneur.2017.00616 

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6. Wong, N. A., & Bahmani, H. (2022). A review of the current state of research on artificial blue light safety as it applies to digital devices. Heliyon, 8(8), e10282. https://doi.org/10.1016/j.heliyon.2022.e10282 

7. National Eye Institute. Age-Related Macular Degeneration (AMD) | National Eye Institute. www.nei.nih.gov. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/age-related-macular-degeneration#:~:text=Age%2Drelated%20macular%20degeneration%20(AMD)%20is%20an%20eye%20disease. 

8. ‌Raikes, A. C., & Killgore, W. D. (2018). Potential for the development of light therapies in mild traumatic brain injury. Concussion, 3(3), CNC57. https://doi.org/10.2217/cnc-2018-0006

9. Rathod, D. G., Muneer, H., & Masood, S. (2021). Phototherapy. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK563140/

10. Skin Cancer Foundation. (2021, August). UV Radiation. The Skin Cancer Foundation. https://www.skincancer.org/risk-factors/uv-radiation/#:~:text=Ultraviolet%20A%20(UVA)%20has%20a 

11. York, N. R., & Jacobe, H. T. (2010). UVA1 phototherapy: a review of mechanism and therapeutic application. International Journal of Dermatology, 49(6), 623–630. https://doi.org/10.1111/j.1365-4632.2009.04427.x 

12. Sun, L., Su, Y., Jiao, A., Wang, X., & Zhang, B. (2023). T cells in health and disease. Signal Transduction and Targeted Therapy, 8(1). https://doi.org/10.1038/s41392-023-01471-y 

13. NCI Dictionary of Cancer Terms. (2011, February 2). Centers for Disease Control and Prevention. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/cytotoxic-agent 

14. Thakur, J. S., Chauhan, C. G. S., Diwana, V. K., Chauhan, D. C., & Thakur, A. (2008). Extravasational side effects of cytotoxic drugs: A preventable catastrophe. Indian Journal of Plastic Surgery, 41(2), 145. https://doi.org/10.4103/0970-0358.44923

15. Brain Trauma Foundation - Frequently Asked Questions (FAQ). Brain Trauma Foundation. https://braintrauma.org/info/faq#:~:text=According%20to%20the%20CDC%2C%20an. 

16. ‌Katz, D. I., Cohen, S. I., & Alexander, M. P. (2015, January 1). Chapter 9 - Mild traumatic brain injury (J. Grafman & A. M. Salazar, Eds.). ScienceDirect; Elsevier. https://www.sciencedirect.com/science/article/abs/pii/B978044452892600009X 

17.  National Institute of Neurological Disorders and Stroke. (2023, November 28). Traumatic Brain Injury (TBI). National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/traumatic-brain-injury-tbi 

18. Laskowski, R. A., Creed, J. A., & Raghupathi, R. (2015). Pathophysiology of Mild TBI: Implications for Altered Signaling Pathways (F. H. Kobeissy, Ed.). PubMed; CRC Press/Taylor & Francis. https://pubmed.ncbi.nlm.nih.gov/26269903/

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20. Sinclair, K. L., Ponsford, J. L., Taffe, J., Lockley, S. W., & Rajaratnam, S. M. W. (2014). Randomized controlled trial of light therapy for fatigue following traumatic brain injury. Neurorehabilitation and Neural Repair, 28(4), 303–313. https://doi.org/10.1177/1545968313508472

21. Killgore, W. D. S. (2020). Lightening the mood: evidence for blue light exposure in the treatment of post-concussion depression. Expert Review of Neurotherapeutics, 20(11), 1081–1083. https://doi.org/10.1080/14737175.2020.1814147