Literature review Reflection:
The literature review was challenging because firstly, final weeks made it harder to focus on getting the project done. Secondly, I have never done a literature review before, meaning rather than actually trying to prove a point I am rather displaying a correlation. When it came to submitting the 3 articles for the review, it was difficult because I had to find articles that had the same exact specific variables and demonstrated a possible correlation rather than proving a point. I changed my topic from artificial food colorings causing health problems, then too Red 40 causes food problems, then Blue lighting impacts on sleep. The last topic was the one I chose because it had specific variables and had enough recent evidence to write the literature review about. From doing this Project I learned that when it comes to researching a topic, it’s
Emely Ortiz
English 21300
Literature Review Final Draft
The Effects Of Evening Blue Lighting And The Next Day Performance.
Abstract
Sleep is crucial for mental and physical health and performance. However, the use of screen time before bed may inhibit the quality of sleep. Because many screens can release blue spectrum lighting, there have been several studies on how blue lighting can negatively impact sleep and how it influences our activity the next day. Several studies have examined how screen time before bed has influenced sleep latency, melatonin secretion, mental and physical performance, etc. Recent research has examined the effects of blue light exposure before bed on sleep patterns, melatonin secretion, and the next day functioning. These experiments include controlled blue-light exposure, questionaries, salvia sampling, and correlated results of higher blue light intensity with higher sleep disruption and poor overall functioning the next day. Observational research has reported excessive nighttime smartphone usage at night with poor sleep quality. Although these studies have only been conducted on young adults, the reviewed literature illustrates that nighttime blue exposure may deteriorate both sleeping and daytime performance.
Introduction
The widespread habit of screen usage before bed has been correlated with disruption in sleep, and mental and physical impairment the next morning. Many researchers have investigated several factors that could have electronics deteriorating sleep. One feature is blue lighting. Depending on the electronic type, screens often emit blue light at different wavelengths. Current literature consistently deems blue lighting to be the primary factor in sleep disruption.
The reason blue lighting can impair the quality of sleep is because of Melanopic irradiance. Melanopic irradiance is when blue lighting stimulates intrinsically photosensitive retinal ganglion cells (ipRGCs). Certain wavelengths of light cause these cells to be stimulated to reduce melatonin secretion. Melatonin is a hormone that causes people to fall asleep and align with their circadian rhythm. Reduced melatonin secretion causes an increase in alertness and delayed sleep latency. Several studies on participants in their prime have researched how blue lighting affects sleep through screen usage habits, and sleep routines, and measuring mental and physical performances the next day. Current literature suggests that evening blue-light exposure can suppress melatonin secretion, damage sleep quality, and the next day’s functioning.
Blue lighting and Melanopic Irradiance
One study infers that Melanopic irradiance from blue light can affect melatonin secretion, sleep latency, and alertness. (Schöllhorn et al. 2023) The experiment was done on 72 male participants between 19 and 35, who were exposed to 4 hours of blue lighting from screen displays before bed. (Schöllhorn et al. 2023), Instead of using actual interactive devices such as phones or tablets. The researchers used an experimental screen display to provide blue light. Using screen displays was important because every electronic emits a different amount of blue light, and every participant could be using the device for different digital content, thus different mental stimulation, and misleading sleep results. The study used blue light alone for more exact results.
Each screen display would emit different amounts of wavelengths or emit blue light to match different actual devices. (Computer screens: 80 lx, tablets: 40 lx, smartphones: 20 lx, watching television: 10 lx). (Schöllhorn et al. 2023) Their time to fall asleep would be measured by a polysomnography (PSG). The melatonin concentration would be measured every night and morning via saliva sampling.
The study indicated that the participants exposed to higher blue lighting intensity experienced higher melanopic irradiance due to lower melatonin concentration in their salvia. The PSG reported that some of the participants spent less than 70% of their time sleeping. (Schöllhorn et al. 2023). Their sleeping latency increased significantly. The research methods of using blue lighting alone and measuring physical effects such as saliva sampling and PSG suggest that blue light alone can highly suppress melatonin secretion. Which has caused the participants to damage their onset and quality of sleep.
Evening Smartphone Exposure and next-day performance.
The second study that measures the effects of blue lighting on sleep and next day performance is and the next day performance was an experiment’s research was performed in Tunisia on 16 elite soccer players aged 18-21 from The Tunisian Premier League. (Didri et al. 2026) The participants were either exposed to 5 hours of screen time or read magazines before going to bed. The experimental group used smartphones while the control group would read magazines before bed. Due to the study being a crossover. They would either use smartphones or read magazines for 5 nights straight then have a “1-week washout period” to return the players back to their original mental state, then switch to either reading or smartphone usage. (Didri et al. 2026). Researchers would then measure their sleep quality, cognition, and physical activity the next morning and then in the afternoon.
To measure sleep quality, they would measure how long they slept and to measure their cognition the players would perform attention, reaction time, and decision-making tests. The players would perform exercises to measure their physical performance the morning after. (Didri et al. 2026). Like the findings of the first study. The sleep results from when each group used phones before bed experienced poor sleep quality and drowsiness during the daytime. The cognitive test results after evening phone use revealed slower reaction times and shorter attention spans. The physical assessment results after phone use before bed had slower and less physical performance than those that did not use a phone before bed. (Didri et al. 2026).
The association with phone usage before bed portrays how much their performance is threatened with poor sleep. The study being a crossover is also important because it creates more accurate data by comparing participants before and after receiving smartphone exposure before bed. One limitation of the study is that it does not prove that blue lighting was the main cause of sleep deterioration because compared to the first study, this experiment only used smartphones. Meaning blue light and digital content could have caused the participants to stay awake. However, both studies suggest that blue-light exposure before sleep can inhibit sleep quality and performance the next day.
The relationship of chronic Smartphone usage before bed and poor sleep
The third article (Goel et al., 2023) reports a link between poor sleep and excessive smartphone habits. 264 medical students from Doon Medical College in Dehradun India, aged between 17 and 25 years took part in this research. In contrast to the other experimental studies, this observational study only surveyed the students with questionnaires based on their sleeping habits at one time. The PSQI (Pittsburg Sleep Quality index) was one of the surveys used in the study. (Goel et al., 2023). The PSQI surveyed how efficiently the students slept, their sleeping habits, any medications they received, their performance during the daytime, etc.
A score higher than 5 on the PSQI was considered poor sleep quality. Around 90% reported that they take their smartphone to bed with them prior to the study. The survey findings associated higher smartphone usage before bed with lower sleep quality. (Goel et al. 2023) Around 48.3% scored above the PSQI and was considered poor sleep quality. Approximately 90% of students took their phones to bed. The connection between smartphone usage and daytime inefficiency was (p<0.001). Meaning there was a 0.1% probability of daytime dysfunction that was unlikely due to other circumstances. (Goel et al. 2023). These results are troubling because, like the Tunisian soccer athletes, medical students need sleep to restore memory and cognitive skills for their rigorous courses. Thus, displaying chronic screen exposure before bed can cause mental health and performance.
Limitations of the studies
Despite the reviewed studies displaying a link between screen usage and sleep impairment. There are limitations. For example, all three of the studies focus on people in their prime, thus the studies cannot be generalized to every age group. Additionally, only the first study measured with blue light alone, thus despite the other screens in each of the other studies emitted blue light they also delivered other factors that could have caused sleep impairment such as digital content.
Conclusion
To conclude, many electronic screens can release blue spectrum lighting, which may negatively impact sleep and how it influences our activity the next day. Recent research has examined the effects of blue light exposure before bed on sleep patterns, melatonin secretion, and the next day functioning. These experiments include controlled blue-light exposure, questionaries, salvia sampling, and correlated results of higher blue light intensity with higher sleep disruption and poor overall functioning the next day. While observational research has reported concerning data with excessive nighttime smartphone usage at night with poor sleep quality. Together, these 3 studies provide behavioral and physiological data. Although these studies have only been conducted on young adults, the reviewed literature illustrates that nighttime blue exposure may deteriorate both sleeping and daytime performance.
Word Count: 1429
Reference Page:
I Schöllhorn, Stefani O, Lucas RJ, Spitschan M, Slawik HC, Cajochen C. 2023. Melanopic irradiance defines the impact of evening display light on sleep latency, melatonin and alertness. 6(1). doi:https://doi.org/10.1038/s42003-023-04598-4.
Dridi N, Souissi MA, Dridi R, Ceylan Hİ, Bragazzi N, Salem A, Fekih S, Chtara M, Mkaouer B, Chtourou H, et al. 2026. Evening smartphone exposure impairs sleep quality and next-day performance in elite soccer players: a randomized controlled trial. Biology of Sport. doi:https://doi.org/10.5114/biolsport.2026;43(1):227-242.
Goel A, Moinuddin A, Tiwari R, Sethi Y, Suhail M, Mohan A, Nirja Kaka, Parth Sarthi, Dutt RD, Ahmad SF, et al. 2023. Effect of Smartphone Use on Sleep in Undergraduate Medical Students: A Cross-Sectional Study. Healthcare. 11(21):2891–2891. doi:https://doi.org/10.3390/healthcare11212891.
