Optimise Light

This study explored how lighting levels affect sleep quality in young adults, testing bright light (450 lux) for focus and low light (220 lux) for calmness. Six participants aged 21–24 engaged in lighting interventions for 20 minutes daily over a week. Results showed improved sleep quality on days with low light exposure in the evening, supporting its calming effects. Bright light improved daytime focus but contributed to evening alertness, potentially disrupting sleep. These findings highlight the importance of managing light exposure to enhance sleep and cognitive health.

This study investigated the relationship between light exposure and sleep quality, timing, and daytime alertness in 59 UK adults using wearable light sensors and sleep diaries. It found that exposure to bright light in the morning reduced sleep inertia (morning grogginess) and improved daytime alertness, while excessive light exposure in the evening and during sleep delayed bedtime and increased sleep onset latency. Most participants failed to meet recommended light exposure levels, highlighting the importance of well-timed light exposure to support circadian health, sleep quality, and cognitive function.

This study tested the impact of different light color changes on the human circadian system and sleep quality using precise, controlled light conditions. Sixteen participants were exposed to three light settings (baseline, blue-dim, yellow-bright) for one hour at night. Results showed no significant differences in melatonin suppression, sleep onset, or quality among the light settings, suggesting that light color changes alone are not major influencers of the circadian clock under typical room lighting. Melanopsin, a light-sensitive pigment, was reaffirmed as the primary driver of circadian responses, not cone-specific color vision pathways.

This review explores how light influences circadian rhythms, sleep, and mood. Light exposure regulates the body’s master clock in the brain, affecting sleep timing, quality, and alertness. Morning light advances sleep schedules, while evening light delays them, impacting melatonin levels. Excessive artificial light, particularly blue light from screens, disrupts sleep and mood. However, light therapy—exposure to bright light during specific times—can improve sleep, stabilize mood, and treat disorders like depression and circadian rhythm sleep disorders. These findings underline the importance of managing light exposure for optimal brain health and cognitive performance.

This randomized study examined the effects of red light on sleep and mood in both healthy participants and individuals with insomnia. Red light exposure one hour before bedtime improved subjective alertness but also increased negative emotions and anxiety, especially in individuals with insomnia. While red light shortened sleep onset latency, it fragmented REM sleep and lowered overall sleep efficiency. These findings suggest red light may not be ideal for sleep, as its emotional and physiological impacts can disrupt restorative processes crucial for cognitive and emotional health.

This study examined how evening home lighting affects the circadian system and sleep using wearable spectrophotometers to measure light exposure. It found that energy-efficient lighting, such as LED and fluorescent lights, emitted higher melanopic illuminance (blue light levels) compared to incandescent lights. About half of homes had lighting bright enough to suppress melatonin by 50%, delaying sleep onset and increasing wakefulness. These findings highlight the impact of artificial light on circadian disruption, poor sleep quality, and related health outcomes like mood and cognitive impairments.

This study investigated the effects of using light-emitting eReaders versus printed books before bedtime. Participants who read eReaders took longer to fall asleep, experienced a delay in their circadian clock, and had suppressed melatonin levels. This also reduced the amount of REM sleep and left participants feeling groggier and less alert the next morning compared to reading printed books. These findings highlight the adverse impact of blue light emitted by eReaders on sleep quality, circadian rhythm alignment, and next-day cognitive performance, emphasizing the need for mindful use of electronic devices at night.

The Healthline article discusses a study published in the Journal of Pineal Research that examines the impact of natural light exposure on sleep quality. The study suggests that insufficient exposure to natural light during the day, particularly in the morning and midday, may lead to sleep disturbances at night. This is attributed to the role of natural light in regulating circadian rhythms, which are essential for maintaining healthy sleep-wake cycles. The findings imply that spending time outdoors, even on overcast days, can enhance sleep quality. Improved sleep is crucial for brain health, as it facilitates memory consolidation and cognitive function. To support cognitive performance, incorporating daily exposure to natural light, engaging in regular physical activity, and adhering to a consistent sleep schedule are recommended. These suggestions align with established sleep hygiene practices and are supported by current scientific understanding of circadian biology.

The Verywell Health article discusses how exposure to morning sunlight can enhance sleep quality by regulating the body's circadian rhythm. Morning light exposure helps synchronize the internal sleep-wake cycle, promoting alertness during the day and facilitating earlier sleep onset at night. This alignment is crucial for cognitive functions such as memory consolidation and emotional regulation. For individuals with sleep disorders, incorporating morning light therapy can be an effective component of treatment. Natural sunlight is the most potent form of light therapy; however, for those unable to access direct sunlight, light boxes emitting artificial light can serve as helpful alternatives. The article's recommendations are grounded in scientific research on circadian biology and sleep medicine, underscoring the importance of light exposure in maintaining optimal brain health and cognitive performance.

This case-control pilot study examined the impact of natural light exposure in office environments on sleep quality and overall health. Office workers with access to windows had significantly better sleep quality, longer sleep duration (46 minutes more per night), and greater physical activity compared to those in windowless environments. Increased light exposure was associated with reduced sleep disturbances and higher vitality. These findings emphasize the importance of natural light in workplaces for enhancing sleep, mood, and cognitive function, benefiting both individual well-being and workplace productivity.

The Healthline article discusses the impact of sleeping with lights on, highlighting that exposure to light during sleep can disrupt the production of melatonin, a hormone that regulates sleep-wake cycles. This disruption may lead to difficulties in achieving deep, restorative sleep stages, resulting in daytime fatigue and impaired cognitive functions such as memory and concentration. To promote better sleep quality and support brain health, the article recommends creating a dark sleeping environment by turning off lights, using blackout curtains, and minimizing exposure to screens before bedtime. These suggestions are based on scientific understanding of circadian rhythms and the role of melatonin in sleep regulation, underscoring the importance of darkness for optimal sleep and cognitive performance.

The sleep Foundation article examines how light exposure affects sleep quality and its subsequent impact on brain health and cognitive performance. It explains that light exposure, particularly blue light from electronic devices, can suppress melatonin production, a hormone that regulates sleep-wake cycles, leading to difficulties in falling asleep and maintaining restful sleep. Disruptions in sleep can impair cognitive functions such as memory consolidation, attention, and decision-making. To enhance sleep quality and support brain health, the article recommends minimizing exposure to screens before bedtime, using dim lighting in the evening, and creating a dark sleeping environment. These suggestions are based on scientific research highlighting the importance of light management in maintaining healthy sleep patterns and optimal cognitive function.

This study examined how light exposure behaviors influence mood, memory, sleep quality, and circadian rhythm in 301 adults. Spending more time outdoors and using tunable lights in the morning improved mood and sleep quality, while late-night mobile phone use delayed sleep schedules and worsened memory, concentration, and perceived sleep quality. Limited use of blue light filters indoors during the day also impacted circadian rhythms negatively. These findings underscore the importance of managing light exposure patterns to optimize cognitive and emotional health.

This study explored the effects of light exposure during sleep on cardiometabolic health. Twenty healthy adults were exposed to dim light or room light (100 lux) over two nights. sleeping under room light increased heart rate and reduced heart rate variability, indicating elevated sympathetic nervous system activity. Participants exposed to light showed higher insulin resistance the following morning compared to those in dim light. These findings suggest that even moderate light exposure during sleep disrupts cardiometabolic regulation, potentially contributing to health issues like diabetes and metabolic syndrome.

This field study assessed how light exposure timing and intensity impact sleep quality and architecture in 20 young adults. Participants wore light and sleep monitors, revealing that late evening or low-intensity light exposure increased sleep disturbances, while early bright light improved slow-wave sleep (SWS) accumulation and reduced sleep onset latency. Late light exposure delayed circadian rhythms, leading to less restorative REM sleep and increased awakenings. The study highlights the importance of well-timed and adequate light exposure for maintaining optimal sleep patterns and brain health.

This systematic review synthesizes findings from 128 studies on the effects of artificial and natural light exposure on human circadian rhythms, focusing on melatonin suppression and REM sleep impacts. Evening and night-time exposure to blue light (460 nm) suppressed melatonin and delayed circadian phases, disrupting sleep. Shorter wavelengths (424 nm) had the strongest suppressive effects. Light also affected REM sleep timing. Sensitivity to light was influenced by individual factors such as age and chronotype. The review underscores the importance of reducing evening light exposure to mitigate health risks linked to circadian disruption, including sleep disorders and metabolic and mental health issues.

This study investigated how daytime exposure to circadian-effective light affects sleep and mood in 109 office workers over winter and summer. Workers exposed to higher levels of morning light experienced better sleep quality, shorter sleep onset latency, and lower rates of depression compared to those with low light exposure. Full-day high light exposure also improved circadian synchronization and mood. The study highlights the importance of proper light exposure in indoor work environments to support sleep health and emotional well-being, particularly in seasons with less natural daylight.

This systematic review examined the effects of blue light exposure on sleep, performance, and well-being in young adults. Blue light reduced sleep quality, sleep duration, and sleep efficiency in many studies, while increasing sleep latency. However, it also enhanced cognitive performance, alertness, and reaction time in more than half the cases. Subjective well-being and mood showed mixed results, with some improvement in positive mood and reduced irritability but not consistently across studies. These findings reveal that blue light has both potential benefits and risks, underscoring the need for context-specific usage to balance performance gains with possible sleep disruption.