Light Therapy Assignment Sample

Subject Name : Psychology

Light Therapy in Treating Sleep/Wake Dysregulation of Parksinson’s Disease

Introduction

Sleep/wake patterns or circadian rhythm in the body which refers to the sleep and wake cycles that are controlled neurobiologically (Albreiki, 2017). However, this cycle may get dysregulated in certain neurodegenerative health conditions like Parkinson’s. To treat this anomaly in the sleep/ wake patterns, combinatorial therapies like light therapy can be used. Light therapy can impact the circadian dysregulation in a Parkinson’s disease (PD) patient, with the use of entrainment to help regulate the sleep/wake cycle to assist the sleep disturbances. PD is the second most common neurodegenerative disorder globally impacting about 1.6-1.8% of the population aged above 50 years. (De Berardis et al., 2013).

Parkinson’s disease is a neurodegenerative disorder that impacts the quality of life and has been linked to decreased dopamine through a loss of dopaminergic neurons in the substantia nigra, in the brainstem. The disease is associated with motor disturbances and non-motor symptoms (NMS). The NMS involves sleep and circadian disturbances, mood changes, cognitive impairments, and autonomic dysregulation (Lazzari, Zordan&Sandrelli, 2018). PD has several genetic and environmental etiologies with undetermined cause (Baldwin & Schwartz, 2012).

This essay will highlight the potential significance of light therapy in regulating the sleep/wake cycle of the patients suffering from Parkinson’s disease. The biophysical and anatomical changes that occur in the body in association with light perception and sleep/wake cycle modulations have also been discussed. Further, future prospects to address the existing lacuna in the application of therapy have also been identified in this paper.

Anatomical Changes

The circadian system is a series of clocks that are generated by a pacemaker and integrated at the level of the organism (Barone, 2017). Through this network, the external zeitgeber in synchronization with sleep/wake cycles (Mantovani, 2017). The process of synchronization or entrainment relies on light to influence sleep/wake or light/dark cycles in both animals and humans. Dysregulation in the circadian rhythms impacts the sleep patterns in individuals associated with PD (Ortuño-Lizarán, Esquiva, Beach, Serrano, Adler, Lax & Cuenca, 2018). Since circadian rhythms are essentially controlled by the neuro biophysical phenomenon, its relationship with neurodegenerative disorders has been largely studied. Recent studies have indicated that targeting sleep and circadian alterations may slow down the symptoms of PD (Mantovani, Smith, Gordon & O’Sullivan, 2017; Lazzari, Bisaglia, Zordan&Sandrelli, 2018).

These rhythms are regulated by both physiological as well as behavioral processes that help in maintaining the 24-hour clock of the body. However, physiological determinants are yet to be discovered (Lazzari et al., 2018). Circadian rhythm dysregulation is an important etiologic factor with sleep disturbances (Annette et al., 2017). Light plays a significant role in this regulation (Giménez, Beersma, Bollen, Linden &Gordijn, 2014). Light enters the retina through the retinohypothalamic path or optic nerve that controls the suprachiasmatic nucleus (SCN) (Hamilton et al., 2018). The suprachiasmatic nucleus creates the circadian rhythm through cells and enables the rhythm with sleep. (Hamilton et al., 2018)

The SCN organizes body temperature, hormone secretion, and sleep. The SCN also connects to the pineal gland and regulates the information to release melatonin. When the SCN processes this information on light and dark, it controls the sleep/wake cycle by releasing the melatonin or inhibiting it and therefore completely influencing the circadian rhythms. There are special retinal ganglion cells (ipRGCs) that respond to light and are sent through the retinohypothalamic tract to the hypothalamus in the area of the SCN (Bonmati-Carrion et al., 2014).

Non-cone and non-rod receptors that are present in the blind humans and have also been found in mice present another class of retinal receptors that play a crucial role in responding to light (LeGates, Fernandez &Hattar, 2014). It has been studied that ipRGCs that belong to a class of retinal ganglion cells, that are present near the nose, have a photopigment known as “melanopsin” that is a light-sensitive retinal protein that also contributes towards the light perception (Bonmatti et al., 2014).

Patients with PD also develop several visual problems. These include problems associated with contrast sensitivity, color vision, and visual acuity. Interestingly, it has also been found that these problems are also linked with circadian rhythm fluctuations and light perception (Lazzari et al., 2018). In a comprehensive study conducted by Cuenca et al. (2018), it was revealed that morphological changes of human melanopsin-containing retinal ganglion cells (mRGCs) occurs in PD. The study aimed to identify if the sleep and circadian function of an individual are interlinked. To assess this, the study included patient’s postmortem with and without PD and found that PD patients had a decreased density of mRGCs, due to death or lost melanopsin (Carey, Devine, Hill &Szucs, 2017).

This study served as a piece of embarking evidence to establish the link between sleep disruption and its impact on mRGCs and retina. In patients with PD, sleep is significantly impaired and this also affects the overall body function in these patients. An irregular amount of dopamine is produced in the body due to the reduced amount of light entering the retina due to altered sleep/wake cycles. Dopamine levels ensure daily rhythm (Videnovic&Golombek, 2017). The decrease in dopamine can be related to significant alterations of the circadian rhythm and contribute to other health conditions like sleep fragmentation, excessive daytime sleepiness and REM sleep behavior disorder (RBD) also originate in these patients.

Circadian dysregulation has been connected negatively with physical and mental health alongside poor sleep in patients. As circadian rhythm is reliant on light exposure, modifying light exposure patterns have had strong theoretical support (Faulkner et al., 2019). There have been statistically and clinically significant improvements found linking sleep disturbance and timings. The alterations of light exposure patterns are known to improve sleep in patients with PD it found that it may be more beneficial to target specific groups with certain circadian problems and behavioral problems (Contreras, 2016).

Light Therapy

Light therapy or phototherapy is an intervention that is used in the treatment and management of several health conditions by exposure to artificial light (Crowlet& Eastman, 2013). Light reception in humans is regulated by the photoreceptors and chromophore at the molecular level that function in conjunction with cytochrome C (Doyen et al., 2011). This boosts the energy production inside the cells and increases the blood flow through regulation of genes that promote neuronal survival (Mitrofanis,2017) Recent studies have investigated light therapy and its ability to entrain the dysfunctional circadian rhythm of Parkinson’s patients to delay the progression of the symptoms or improve the quality of life (Rutten, Vriend, van den Heuvel, Smit, Berendse& van der Werf, 2012; Johnstone, Coleman, Moro, Torres, Eells, Baker, Ashkan, Stone, Benabid&Mitrofanis, 2014; Barone, 2017; Reiter, 2007).

Light is one of the most crucial elements that can help in the synchronization of physiological rhythms, light-based therapies can be of essential significance for treatment as well as management of health conditions where the regular circadian rhythm of the body is disrupted (Erben, 2013). The therapy is known to affect the chemicals present in the brain that are linked to the sleep and mood of the individuals. Light has been identified as one of the most potent synchronizers of the circadian clock and therefore, the therapy aims to regulate and manage several health conditions that are linked with sleep/wake cycle in the body (Gandhi et al., 2015). In association with Parkinson’s, light therapy is known to impact the patients in two ways.

First, it alters the amount of melatonin produced, and secondly, it is also associated with the management of dopamine levels (Giménez et al., 2014; Faulkner et al., 2019; Boivin & James, 2002; Bromundt et al., 2013). Light intensity and availability have been strongly interlinked with neurodegenerative diseases like Parkinson’s. Geographically, countries that have limited light availability show a 56% more chance of Parkinson's development than those with adequate light availability linking high light intensity to lower risks of PD development (Videnovic&Golombek, 2017).

Multiple studies have been conducted that signal significance of light therapy in the management and treatment of neurodegenerative disorders and PD in specific. In a trial by Videnovic and Golombek (2017), 120 patients of PD were provided with 60 minutes of light therapy with a light intensity of 4000 to 6000 lux before bedtime over a period. The findings revealed significant improvements in mood, anxiety, and motor functions. Participants who quit the therapy also found that their symptoms returned against those who completed light therapy to achieve positive results. This therapy had helped the participants by protecting the damage of dopaminergic neurons through the stimulation of melanopsin by the retinal ganglion cells.

This improved the dopamine levels of the body and helped in the management of PD in the patients by regulating the sleep/wake cycles. Another study with randomized use of bright light therapy was conducted by Bruin, Bittencourt and Tufik (2012) which is focused on developing the placebo effect and managing the sleep/wake cycle in patients with PD. The study included 36 patients with PD where they received half the amount of light but at 7500 lux for 15 days. The therapy showed significant improvements in the patients. It also helped in minimizing tremors and other symptoms of neurodegeneration.

This study was also validated by Rutten et al. (2012), who found that bright light therapy aids in the improvement of sleep quality and sleep efficiency in association with melatonin treatment. The therapy is also known to limit the daytime sleepiness assisting patients with neurodegenerative health conditions. Red and infrared light therapy is also associated with photobiomodulation and improves locomotor behavior in Parkinson's (Mitrofanis, 2017). These studies not only assert the significance of light therapy in the management of PD and its symptoms, but it also provides a successful tool that helps in the analysis of the sleep/wake cycles and how neurodegenerative diseases like Parkinson’s impact the circadian rhythm of the body.

Future Prospects

Light therapy has not only served to be helpful in the protection of neurons but has also been found to repair and rescue the damaged neurons assisting in the complete recovery (Johnstone et al., 2016). Light has a ubiquitous effect on the central nervous system (Mitrofanis, 2017). Therefore, it is not yet completely determined how light therapy functions holistically on the entire body system of an individual. Hence, a significant research gap exists to address the true impact of light on the central nervous system so that a more directed approach can be followed to determine the impact of light wavelength and intensity in assessing its impact on the brain and retina for the regulation of circadian rhythms (Khuller& Atul, 2012).

The role of melanin production and its association with light therapy also requires detailed investigations. Since it has been noted that patients that undergo light therapy might face a relapse once the therapy is aborted, it highlights how this therapy can function as an effective management strategy yet, not a definitive cure for a disease like Parkinson’s and other neurodegenerative disorders (Johnstone et al., 2014). Research needs to deduce how light therapy masks the neurodegeneration in Parkinson’s and what is the cause of relapse post therapies. Identification of these factors through an investigative approach will assure the development of interventions that can have a long-lasting impact on the health of patients suffering from PD and allow for successful regulation of the sleep/wake cycles in the patients (Kofuji et al., 2016).

It is not all bright for the use of light therapy as it is also associated with several side effects. Chronic misuse of light therapy in excessive amounts may impact the health and quality of life in other areas such as depression from too much melatonin (LeGates, Fernandez &Hattar, 2014). It has also been found that people that undergo light therapy for long also tend to sleep more often due to motor issues impacting their overall social life of these patients (Bruin, Bittencourt&Tufik, 2012). A neurodegenerative disorder like PD often manifests in conjunction with psychological illnesses like bipolar disorder (Rieter, 2007). Therefore, light therapy is not suitable for the treatment and management in these individuals as it may increase the chances of mania impacting the overall well being of these individuals. The increase of manic episodes in patients with PD and chronic mental illnesses has been speculated to be associated with an increase of melatonin (Khuller& Atul, 2012).

Hence, it becomes crucial for the researchers to identify the cause of these limitations associated with the therapy and develop modulations that can be applied to a larger population with minimal side effects (Rieter, 2007). Light therapy has several dark spots in research that need to be addressed to identify the biomechanics of its functioning so that a successful intervention can be derived from it for the management and treatment of the patients suffering from sleep/wake cycles due to underlying neurodegenerative disorders like Parkinson's (Sparla et al., 2018). Future research, therefore, must aim to help to improve the efficiency of the therapy and prevent relapse. Further, it will also be crucial to develop alternative models of applications based on wavelength and intensity modulations that can assist in the treatment and management of PD patients along with psychological illnesses to prevent episodes of mania triggered by excessive light usage.

Conclusion

Sleep/wake cycles are an essential component of the overall well being of an individual. However, in certain neurodegenerative disorders like Parkinson’s, the regular circadian rhythm of the body may be lost. This essay highlighted the intricate relationship between the sleep/wake cycles in patients with Parkinson's disease and the availability and reception of light. Light is one of the most essential synchronizers that dictate the body function. This essay highlight how the reception of light can impact the bio physiology and anatomy of the body. The reception of light results in photobiomodulation of the cells that correspond to the effective sleep/wake cycle regulation largely through the production of melatonin and regulation of dopamine.

Light therapy has therefore been used for the effective management of the circadian rhythms in patients with Parkinson’s disease. This essay is also inclusive of some foundational studies that establish the significance light in regulation of the body function and sleep cycles through neuropreventive effect, melatonin production, and biochemical regulation. However, the therapy application has been crude leaving several research gaps that can be addressed in future research. The true cause and consequence of the efficacy of light therapy are not known as the action of light on the central nervous system has been considered to be ubiquitous.

Further, the therapy cannot be applied to patients with underlying psychological illnesses that are often accompanied by PD as it may trigger episodes of mania in the patient. Future research must, therefore, target on limiting the side effects of light therapy and enhancing its efficacy for application. Modulations based on the light intensity, wavelength, and duration are also required to promote the widespread application of the therapy for the treatment and management of circadian rhythms in patients suffering from PD.

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