Blue-enriched White Light Research Articles

Evaluation of the effects of blue-enriched white light on cognitive performance, arousal, and overall appreciation of lighting.

Light's non-visual effects on the biological clock, cognitive performance, alertness, and mental health are getting more recognized. These are primarily driven by blue light, which triggers specific retinal cells containing melanopsin. Traditionally, research on light has relied on correlated color temperature (CCT) as a metric of its biological influence, given that bluer light corresponds to higher Kelvin values. However, CCT proves to be an inadequate proxy of light's biological effects. A more precise metric is melanopic Equivalent Daylight Illuminance (mel-EDI), which aligns with melanopsin spectrum. Studies have reported positive cognitive impacts of blue-enriched white light. It's unclear if the mixed results are due to different mel-EDI levels since this factor wasn't assessed. Given recent recommendations from experts to aim for at least 250 mel-EDI exposure daily for cognitive benefits, our aim was to assess if a 50-minute exposure to LED light with 250 mel-EDI could enhance concentration and alertness, without affecting visual performance or comfort compared to conventional lighting producing around 150 mel-EDI. To ensure mel-EDI's impact, photopic lux levels were kept constant across conditions. Conditions were counterbalanced, parameters included subjective sleepiness (KSS; Karolinska Sleepiness Scale), concentration (d2-R test), visual performance (FrACT; Freiburg Visual Acuity and Contrast Test), general appreciation (VAS; Visual Analogous Scale), preferences and comfort (modified OLS; Office Lighting Survey). The experimental light significantly reduced sleepiness (p = 0.03, Cohen's d = 0.42) and also decreased contrast sensitivity (p = 0.01, Cohen's d = 0.50). The conventional light was found to be more comfortable (p = 0.002, Cohen's d = 0.62), cheerful (p = 0.02, Cohen's d = 0.46) and pleasant (p = 0.005, Cohen's d = 0.55) while the experimental light was perceived as brighter (p = 0.004, Cohen's d = 0.58) and tended to be more stimulating (p = 0.10). Notably, there was a preference for conventional lighting (p = 0.004, Cohen's d=0.56) and concentration was equally improved in both conditions. Despite the lack of further improvement in concentration from exposure to blue-enriched light, given the observed benefits in terms of vigilance, further research over an extended period would be justified. These findings could subsequently motivate cognitive optimization through lighting for workers that would benefit from artificial lighting such as in northern regions.

Effectiveness of caffeine and blue-enriched light on cognitive performance and electroencephalography correlates of alertness in a spaceflight robotics simulation

Human cognitive impairment associated with sleep loss, circadian misalignment and work overload is a major concern in any high stress occupation but has potentially catastrophic consequences during spaceflight human robotic interactions. Two safe, wake-promoting countermeasures, caffeine and blue-enriched white light have been studied on Earth and are available on the International Space Station. We therefore conducted a randomized, placebo-controlled, cross-over trial examining the impact of regularly timed low-dose caffeine (0.3 mg per kg per h) and moderate illuminance blue-enriched white light (~90 lux, ~88 melEDI lux, 6300 K) as countermeasures, separately and combined, in a multi-night simulation of sleep-wake shifts experienced during spaceflight among 16 participants (7 F, ages 26–55). We find that chronic administration of low-dose caffeine improves subjective and objective correlates of alertness and performance during an overnight work schedule involving chronic sleep loss and circadian misalignment, although we also find that caffeine disrupts subsequent sleep. We further find that 90 lux of blue-enriched light moderately reduces electroencephalogram (EEG) power in the theta and delta regions, which are associated with sleepiness. These findings support the use of low-dose caffeine and potentially blue-enriched white light to enhance alertness and performance among astronauts and shiftworking populations.

Effects of caffeine and blue-enriched light on spare visual attention during simulated space teleoperation

Safe and successful operation of the International Space Station robotic arm is a complex task requiring difficult bimanual hand coordination and spatial reasoning skills, adherence to operating procedures and rules, and systems knowledge. These task attributes are all potentially affected by chronic sleep loss and circadian misalignment. In a randomized, placebo-controlled, cross-over trial examining the impact of regularly timed low-dose caffeine (0.3 mg kg−1 h−1) and moderate illuminance blue-enriched white light (~90 lux, ~88 melEDI lux, 6300 K), 16 participants performed 3 types of realistic robotic arm tasks using a high-fidelity desktop simulator overnight. Our goal was to determine how these countermeasures, separately and combined, impacted telerobotic task performance and the ability to allocate attention to an unrelated secondary visual task. We found that all participants maintained a similar level of robotic task performance throughout the primary task but the application of caffeine separately and with blue-enriched light significantly decreased response time to a secondary visual task by −9% to −13%, whereas blue-enriched light alone changed average response times between −4% and +2%. We conclude that, for sleep-restricted individuals, caffeine improved their ability to divide their visual attention, while the effect of blue-enriched light alone was limited. Light and caffeine together was most effective. Use of these countermeasures should improve the margin of safety if astronauts perform familiar tasks under degraded conditions or novel tasks where task workload is increased.

Effect of Personalized Blue-Enriched White Light Intervention on Rest-Activity and Light Exposure Rhythms in Mild and Moderate Alzheimer's Disease.

We aimed to examine the effectiveness of personalized light intervention using a blue-enriched light-emitting-diodes device on rest-activity rhythm (RAR) and light exposure rhythm (LER) in patients with mild and moderate Alzheimer's disease (AD). AD patients with poor sleep quality and/or insomnia symptoms were assigned into either an experimental group (EG) or control group (CG) in a single-blind design. Personalized light intervention was given at 9-10 h after individual dim light melatonin onset, lasting for 1 h every day for two weeks in the EG (77.36±5.79 years, n=14) and CG (78.10±7.98 years, n=10). Each patient of CG wore blue-attenuating sunglasses during the intervention. Actigraphy recording at home for 5 days was done at baseline (T0), immediate postintervention (T1), and at four weeks after intervention (T2). The variables of RAR and LER were derived using nonparametric analysis. We found a significant time effect on the intradaily variability (IV) of RAR at T2 with respect to T0 (p=0.039), indicating reduced IV of RAR at four weeks after personalized light intervention regardless of blue-enriched light intervention. There was a time effect on the IV of LER at T1 with respect to T0 (p=0.052), indicating a reduced tendency in the IV of LER immediately after intervention. Our personalized light intervention, regardless of blue-enriched light source, could be useful in alleviating fragmentation of RAR and LER in AD patients.

Impact of light on task-evoked pupil responses during cognitive tasks.

Light has many non-image-forming functions including modulation of pupil size and stimulation of alertness and cognition. Part of these non-image-forming effects may be mediated by the brainstem locus coeruleus. The processing of sensory inputs can be associated with a transient pupil dilation that is likely driven in part by the phasic activity of the locus coeruleus. In the present study, we aimed to characterise the task-evoked pupil response associated with auditory inputs under different light levels and across two cognitive tasks. We continuously monitored the pupil of 20 young healthy participants (mean [SD] 24.05 [4.0] years; 14 women) whilst they completed an attentional and an emotional auditory task whilst exposed to repeated 30-40-s blocks of light interleaved with darkness periods. Blocks could either consist of monochromatic orange light (0.16 melanopic equivalent daylight illuminance (EDI) lux) or blue-enriched white light of three different levels [37, 92, 190 melanopic EDI lux; 6500 K]. For the analysis, 15 and then 14 participants were included in the attentional and emotional tasks, respectively. Generalised linear mixed models showed a significant main effect of light level on the task-evoked pupil responses triggered by the attentional and emotional tasks (p ≤ 0.0001). The impact of light was different for the target versus non-target stimulus of the attentional task but was not different for the emotional and neutral stimulus of the emotional task. There is a smaller sustained pupil size during brighter light blocks but, a higher light level triggers a stronger task-evoked pupil response to auditory stimulation, presumably through the recruitment of the locus coeruleus.

Effects of blue-enriched white light with same correlated colour temperature on visual fatigue

Visual fatigue has become a public health issue, while the relevant retinal mechanism and characteristics of blue light that induce visual fatigue have been rarely studied. In the retina, both short wavelength-sensitive (S) cones and melanopsin-containing intrinsically photoreceptive retinal ganglion cells (ipRGCs) are sensitive to blue light, and their responses are opposite in pupil mediation. Thus, effects of blue-enriched white light with different S-cone-opic Equivalent Daylight Illuminance (EDI) on visual fatigue was investigated, maintaining the same melanopic EDI to avoid interferences of melanopsin-containing ipRGCs. Two white illuminants (one with low S-cone-opic EDI, the other with high S-cone-opic EDI) were characterized based on α-opic EDI with the same correlated colour temperature and illuminance. Melanopic EDI was lower than S-cone-opic EDI of these two illuminants. Psychological, visual, physiological and cognitive performances were measured to investigate visual fatigue. Results showed that blue-enriched white light with high S-cone-opic EDI can induce visual fatigue. Participants felt more discomfort in their eyes under high S-cone-opic EDI along with the decline of tear film stability and changes of heart rhythm. Furthermore, the reaction time in a memory task increased significantly under high S-cone-opic EDI. The findings provide new insights into the optimization of indoor lighting environments for human health.

Optimised Stable Lighting Strengthens Circadian Clock Gene Rhythmicity in Equine Hair Follicles.

Hair follicles (HF) represent a useful tissue for monitoring the circadian clock in mammals. Irregular light exposure causes circadian disruption and represents a welfare concern for stabled horses. We aimed to evaluate the impact of two stable lighting regimes on circadian clock gene rhythmicity in HF from racehorses. Two groups of five Thoroughbred racehorses in training at a commercial racehorse yard were exposed to standard incandescent light or a customized LED lighting system. The control group received light from incandescent bulbs used according to standard yard practice. The treatment group received timed, blue-enriched white LED light by day and dim red LED light at night. On weeks 0 and 20, mane hairs were collected at 4 h intervals for 24 h. Samples were stored in RNAlater at -20 °C. RNA was isolated and samples interrogated by quantitative PCR for the core clock genes: ARNTL, CRY1, PER1, PER2, NR1D2, and the clock-controlled gene DBP. Cosinor analyses revealed 24 h rhythmicity for NR1D2 and PER2 and approached significance for CRY1 (p = 0.013, p = 0.013, and p = 0.051, respectively) in week 20 in the treatment group only. No rhythmicity was detected in week 0 or in week 20 in the HF of control horses. Results suggest that lighting practices in racehorse stables may be improved to better stimulate optimum functioning of the circadian system.

Permissible viewing times of educational projector and TV

Projectors have become one major medium in modern teaching, with large area-size displays emerging as an alternative. What concerns the general public is whether such eLearning would impose threat on eyes, by noting blue enriched white light to be hazardous to retina and else. Especially, little was known about their permissible viewing time under a certain viewing clarity. We had hence carried out a quantitative study with the use of a blue-hazard quantification spectrometer to determine the permissible viewing time when using a projector and a large size TV screen for displaying. Surprisingly, the large TV screen could permit a much longer viewing time, meaning which is more eye-friendly. It is plausibly because its resolution is much higher than that of the projector. Two dilemmas were observed in such eLearning; those sitting in the front would suffer a much higher illuminance, leading to a much shorter viewing time, while those sitting in the back would need a far much larger font size to see clearly. To ensure both viewing clarity and a sufficiently long permissible viewing time, orange text on black background is suggested to replace the defaulted black text on white background. The permissible viewing time could hence drastically increase from 1.3 to 83 h at 2 m by viewing a 30 pt font for the TV and from 0.4 to 54 h for the projection. At 6 m, the permissible viewing time was increased from 12 to 236 h for the TV and from 3 to 160 h for the projection, based on a viewable 94 pt font. These results may help educators and other e-display users to wisely apply the display tools with safety.

Using Light to Facilitate Circadian Entrainment from Day to Night Flights.

BACKGROUND: As part of a larger project to provide recommendations regarding limitations and best practices for shifting aviators from day to night operations, a study was conducted to assess the efficacy of high energy visible (HEV) light to shift the circadian rhythm in humans. The study attempted to replicate the patterns of military aviators who could be required to shift abruptly from day to night flight operations.METHODS: Simulated flight performance and salivary melatonin levels of 10 U.S. military aviators were collected over a 3-night period using a within-subject dim light melatonin onset (DLMO) study design. Data were collected in a laboratory with participants returning home to sleep following each of the three evenings/nights of data collection. Light treatment included a single 4-h exposure of blue-enriched white light (∼1000 lux) on night 2. Data collected included melatonin levels, light exposure, sleepiness, cognitive workload, and simulated flight performance.RESULTS: The average delay in melatonin onset was 1.32 ± 0.37 h (range: 53 min to 1 h 56 min). Sleepiness (P = 0.044) and cognitive workload (P = 0.081) improved the night following the light treatment compared to the baseline. No systematic differences were identified in flight performance.DISCUSSION: The HEV light treatment successfully delayed the circadian phase of all participants even though participants' ambient light levels (including daylight) outside the laboratory were not controlled. These findings were used to develop circadian synchronization plans for aviators who are asked to transition from day to night operations. These plans will be assessed in a follow-on study in an operational unit.Shattuck NL, Matsangas P, Reily J, McDonough M, Giles KB. Using light to facilitate circadian entrainment from day to night flights. Aerosp Med Hum Perform. 2023; 94(2):66-73.

Fatigued through everyday life. Interprofessional intervention approaches for dealing with long-term outcomes of fatigue after moderate and severe traumatic brain injury / Erschöpft durch den Alltag. Interprofessionelle Interventionsansätze im Umgang mit Langzeitfolgen von Fatigue nach mittlerem und schwerem Schädel-Hirn-Trauma

Abstract Background Fatigue is a common long-term consequence of moderate and severe traumatic brain injury (TBI). Until now, there are intervention approaches for fatigue after TBI, but not specifically for fatigue after moderate and severe TBI in the outpatient setting. According to the demands of multiple studies, the severity and time since the TBI should be addressed more specifically. Objectives The aim of this study is to provide an overview of the possibilities for interprofessional intervention approaches in fatigue after moderate and severe TBI in the outpatient long-term setting. Based on the International Classification of Functioning, Disability and Health (ICF) the intervention approaches should be made accessible to the interprofessional team. Methods The research question was answered with a systematic review. The databases CINAHL, Pubmed, Medline, Cochrane Library, PsychINFO, Web of Science, AMED and OTseeker were used. The included studies were critically appraised using Law et al. (1998). Results Fatigue after moderate and severe TBI can lead to restrictions in daily life and general productivity. There is also a significant association with sleep disorders, depression, anxiety and vitamin D deficiency. In addition, fatigue persists for several years in more than half of the people affected. Daily light therapy with blue-enriched white light is an effective way to reduce fatigue after TBI. Conclusions Intervention approaches exist in the field of sleep management and coping strategies. Sleep disorders, depression, anxiety and vitamin D deficiency should also be treated if necessary. Due to the limited evidence, the implications for practice are limited.

Impact of Upgraded Lighting on Falls in Care Home Residents.

Falls in care home residents have major health and economic implications. Given the impact of lighting on visual acuity, alertness, and sleep and their potential influence on falls, we aimed to assess the impact of upgraded lighting on the rate of falls in long-term care home residents. An observational study of 2 pairs of care homes (4 sites total). One site from each pair was selected for solid-state lighting upgrade, and the other site served as a control. Two pairs of care homes with 758 residents (126,479 resident-days; mean age (±SD) 81.0 ± 11.7years; 57% female; 31% with dementia). One "experimental" site from each pair had solid-state lighting installed throughout the facility that changed in intensity and spectrum to increase short-wavelength (blue light) exposure during the day (6 am-6 pm) and decrease it overnight (6 pm-6 am). The control sites retained standard lighting with no change in intensity or spectrum throughout the day. The number of falls aggregated from medical records were assessed over an approximately 24-month interval. The primary comparison between the sites was the rate of falls per 1000 resident-days. Before the lighting upgrade, the rate of falls was similar between experimental and control sites [6.94 vs 6.62 falls per 1000 resident-days, respectively; rate ratio (RR) 1.05; 95% CI 0.70-1.58; P= .82]. Following the upgrade, falls were reduced by 43% at experimental sites compared with control sites (4.82 vs 8.44 falls per 1000 resident-days, respectively; RR 0.57; 95% CI 0.39-0.84; P= .004). Upgrading ambient lighting to incorporate higher intensity blue-enriched white light during the daytime and lower intensity overnight represents an effective, passive, low-cost, low-burden addition to current preventive strategies to reduce fall risk in long-term care settings.

Effects of Lighting Interventions to Improve Sleepiness in Night-Shift Workers: A Systematic Review and Meta-Analysis.

Shift work disrupts an otherwise normal circadian rhythm, which may result in sleepiness among night-shift workers. Artificial light has been shown to alter the light–dark cycle of shift workers and reset or phase shift the biological clock, improving nighttime alertness in workers. However, the effect of light therapy on improving sleepiness in nighttime workers has not been effectively confirmed in nursing clinical studies, and it is worth using relevant studies to provide the best evidence in any clinical setting. Systematic review and meta-analysis were used. The study was performed using PRISMA. Academic Search Complete, Embase, MEDLINE, the Cochrane Library, and CINAHL were searched, from the inception of each database to 27 December 2021. The Cochrane risk of bias tool was used to assess the methodological quality of each study. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were synthesized using a random-effects model to assess the efficacy of lighting intervention to improve sleepiness in night-shift workers. Sensitivity analysis followed by subgroup analysis was employed to examine heterogeneity. The meta-analysis was performed using Review Manager 5.4.1 software. A total of 14 studies from 7 countries were included. The overall result shows that lighting interventions significantly improved sleepiness. Further, the blue-enriched white light with a color temperature greater than 5000 Kelvin was effective in improving sleepiness of night-shift workers. This study unveils the emergent knowledge that light interventions with blue-enriched white were effective in improving sleepiness for night-shift workers, including nurses. This finding can be applied to ensure patient safety, reduce accidents, and improve work efficiency and job satisfaction. Nurses constitute the largest health professional workforce. We suggest that hospitals can insert blue-enriched white light equipment for night-shift healthcare providers. Several evidence-based suggestions are made for further consideration.

Dynamic lighting schedules to facilitate circadian adaptation to shifted timing of sleep and wake.

Circadian adaptation to shifted sleep/wake schedules may be facilitated by optimizing the timing, intensity and spectral characteristics of light exposure, which is the principal time cue for mammalian circadian pacemaker, and possibly by strategically timing nonphotic time cues such as exercise. Therefore, circadian phase resetting by light and exercise was assessed in 44 healthy participants (22 females, mean age [±SD] 36.2 ± 9.2 years), who completed 8-day inpatient experiments simulating night shiftwork, which included either an 8 h advance or 8 h delay in sleep/wake schedules. In the advance protocol (n = 18), schedules were shifted either gradually (1.6 h/day across 5 days) or abruptly (slam shift, 8 h in 1 day and maintained across 5 days). Both advance protocols included a dynamic lighting schedule (DLS) with 6.5 h exposure of blue-enriched white light (704 melanopic equivalent daylight illuminance [melEDI] lux) during the day and dimmer blue-depleted light (26 melEDI lux) for 2 h immediately before sleep on the shifted schedule. In the delay protocol (n = 26), schedules were only abruptly delayed but included four different lighting conditions: (1) 8 h continuous room-light control; (2) 8 h continuous blue-enriched light; (3) intermittent (7 × 15 min pulses/8 h) blue-enriched light; (4) 8 h continuous blue-enriched light plus moderate intensity exercise. In the room-light control, participants received dimmer white light for 30 min before bedtime, whereas in the other three delay protocols participants received dimmer blue-depleted light for 30 min before bedtime. Both the slam and gradual advance protocols induced similar shifts in circadian phase (3.28 h ± 0.37 vs. 2.88 h ± 0.31, respectively, p = .43) estimated by the change in the timing of timing of dim light melatonin onset. In the delay protocol, the continuous 8 h blue-enriched exposure induced significantly larger shifts than the room light control (-6.59 h ± 0.43 vs. -4.74 h ± 0.62, respectively, p = .02). The intermittent exposure induced ~60% of the shift (-3.90 h ± 0.62) compared with 8 h blue-enriched continuous light with only 25% of the exposure duration. The addition of exercise to the 8 h continuous blue-enriched light did not result in significantly larger phase shifts (-6.59 h ± 0.43 vs. -6.41 h ± 0.69, p = .80). Collectively, our results demonstrate that, when attempting to adapt to an 8 h overnight work shift, delay shifts are more successful, particularly when accompanied by a DLS with high-melanopic irradiance light stimulus during wake.

0227 The effect of light on circadian entrainment for shifting from day to night flight operations

Abstract Introduction A midair collision during a routine nighttime air refueling training mission in the early morning hours of December 6, 2018, resulted in the tragic deaths of six Marine aircrew members and the loss of two US Marine Corps aircraft. Fatigue and the transition from day to night flights were called out as a problem area that continues to plague aviation commands. The goal of this study was to provide recommendations to the fleet regarding the limitations and best practices for shifting aviators from day to night operations to mitigate aviator fatigue and facilitate circadian re-alignment. Methods Longitudinal (10-day) within-subject assessment of aviators (N=9) in hybrid conditions. Aviators completed validated questionnaires for sleepiness and workload. Performance was assessed in simulated flight scenarios (one morning and three night sessions). The efficacy of a single 4-hour exposure of blue-enriched white light (~1000 lux) was assessed with the dim-light melatonin onset procedure. The study protocol attempted to replicate the work and rest patterns of aviators in the field who work during the day but could potentially be required to quickly shift their schedules to support night flight operations. Results The circadian phase of all participants was successfully delayed an average of 1.3 hours (range: 0.88-1.93 hours). Despite the lack of control over light exposure or other activities over the study period, participants reported less sleepiness and reduced subjective workload with improved flight performance. Conclusion Conclusions from the literature review and our study indicate that circadian entrainment in complex military operational settings should use light management as the dominant method for shifting the circadian clock. Based on these conclusions, we developed general recommendations and two circadian synchronization plans for aircrew switching from day to night operations. One plan shows a schedule that prepares for night operations by steadily shifting the daily schedule over multiple days. The other plan shows a schedule for aircrew who are required to shift from day to night operations abruptly without notice. Support (If Any) Supported by the Assistant Commandant of the Marine Corps.

Endogenous circadian regulation and phase resetting of clinical metabolic biomarkers.

Shiftwork and circadian disruption are associated with adverse metabolic effects. Therefore, we examined whether clinical biomarkers of metabolic health are under endogenous circadian regulation using a 40hours constant routine protocol (CR; constant environmental and behavioral conditions) and evaluated the impact of typical daily conditions with periodic sleep and meals (baseline; 8hours sleep at night, four meals during a 16hour wake episode) on the phase and amplitude of these rhythms. Additionally, we tested whether these circadian rhythms are reset during simulated shiftwork. Under CR (n=16 males, mean age±SD=23.4±2.3years), we found endogenous circadian rhythms in cholesterol, HDL and LDL, albumin and total protein, and VLDL and triglyceride. The rhythms were masked under baseline conditions except for cholesterol, which had near-identical phases under both conditions. Resetting of the cholesterol rhythm and Dim Light Melatonin Onset (DLMO) was then tested in a study of simulated shiftwork (n=25, 14 females, 36.3±8.9years) across four protocols; two with abrupt 8hour delay shifts and exposure to either blue-enriched or standard white light; and either an abrupt or gradual 8hour advance (1.6hours/day over 5days) both with exposure to blue-enriched white light. In the delay protocols, the cholesterol rhythm shifted later by -3.7hours and -4.2hours, respectively, compared to -6.6hours and -4.7hours, for DLMO. There was a significant advance in cholesterol in the abrupt (+5.1hours) but not the gradual (+2.1hours) protocol, compared to +3.1hours and +2.8hours in DLMO, respectively. Exploratory group analysis comparing the phases of all metabolic biomarkers under both studies showed evidence of phase shifts due to simulated shiftwork. These results show that clinical biomarkers of metabolic health are under endogenous circadian regulation but that the expression of these rhythms is substantially influenced by environmental factors. These rhythms can also be reset, which has implications for understanding how both behavioral changes and circadian shifts due to shiftwork may disrupt metabolic function.

Home-based light therapy for fatigue following acquired brain injury: a pilot randomized controlled trial

Background and objectivesFatigue and sleep disturbance are debilitating problems following brain injury and there are no established treatments. Building on demonstrated efficacy of blue light delivered via a lightbox in reducing fatigue and daytime sleepiness after TBI, this study evaluated the efficacy of a novel in-home light intervention in alleviating fatigue, sleep disturbance, daytime sleepiness and depressive symptoms, and in improving psychomotor vigilance and participation in daily productive activity, following injuryMethodsThe impact of exposure to a dynamic light intervention (Treatment) was compared to usual lighting (Control) in a randomized within-subject, crossover trial. Outcomes were fatigue (primary outcome), daytime sleepiness, sleep disturbance, insomnia symptoms, psychomotor vigilance, mood and activity levels. Participants (N = 24, M ± SDage = 44.3 ± 11.4) had mild-severe TBI or stroke > 3 months previously, and self-reported fatigue (Fatigue Severity Scale ≥ 4). Following 2-week baseline, participants completed each condition for 2 months in counter-balanced order, with 1-month follow-up. Treatment comprised daytime blue-enriched white light (CCT > 5000 K) and blue-depleted light (< 3000 K) 3 h prior to sleep.ResultsRandom-effects mixed-model analysis showed no significantly greater change in fatigue on the Brief Fatigue Inventory during Treatment, but a medium effect size of improvement (p = .33, d = -0.42). There were significantly greater decreases in sleep disturbance (p = .004), insomnia symptoms (p = .036), reaction time (p = .004) and improvements in productive activity (p = .005) at end of Treatment relative to Control, with large effect sizes (d > 0.80). Changes in other outcomes were non-significant.ConclusionsThis pilot study provides preliminary support for in-home dynamic light therapy to address sleep-related symptoms in acquired brain injury.Trial registrationThis trial was registered with the Australian and New Zealand Clinical Trials Registry on 13 June 2017, www.anzctr.org.au, ACTRN12617000866303.

Does Bright Light Counteract the Post-lunch Dip in Subjective States and Cognitive Performance Among Undergraduate Students?

The post-lunch dip in alertness and performance was widely experienced during the early afternoon. Taking a short nap was documented as a practical strategy for habitual nappers to counteract the decline of alertness and performance. Yet, it remains unknown whether bright light exposure in the early afternoon working hours could alleviate the performance deficits caused by a post-lunch nap loss for habitual nappers. Seventeen undergraduate students who had a long-term habit of taking a post-lunch nap were assigned to three interventions: (1) a short nap + normal indoor light (100 lx, 4,000 K at eye level); (2) no nap + normal indoor light, and (3) no nap + blue-enriched bright light (1,000 lx, 6,500 K at eye level), in which subjective alertness (Karolinska Sleepiness Scale, KSS), mood (Positive and Negative Affect Schedule, PANAS), and task performance in sustained attention (psychomotor vigilance test, PVT), response inhibition (go/no-go task), and working memory (paced visual serial addition test, PVSAT) were measured. Results showed that a post-lunch nap deprivation significantly increased subjective sleepiness and negative mood and impaired performance in PVT and PVSAT, while exposure to bright blue-enriched white light vs. normal indoor light in the early afternoon significantly relieved such negative effects on mood, sleepiness, and performance in PVSAT; subjective positive mood and performance in PVT and go/no-go task remained unaffected with light intervention. These findings suggested that bright blue-enriched white light exposure could be a potential strategy for those who are suffering from drowsiness and low working memory following a habitual midday nap loss.

Positive effect of timed blue-enriched white light on sleep and cognition in patients with mild and moderate Alzheimer\u2019s disease

Conflicting results have been reported regarding the effectiveness of light treatment (LT) in patients with Alzheimer’s disease (AD). We investigated the effectiveness of blue-enriched white LT on sleep, cognition, mood and behavior in patients with mild and moderate AD. The treatment group (n = 14) sat about 60 cm away from a small (136 × 73 × 16 mm) LED light box for 1 h each morning for 2 weeks. The control group (n = 11) wore dark, blue-attenuating sunglasses during the 1 h exposures. The morning light started 9–10 h after each individual’s dim light melatonin onset (DLMO). Assessments were done at baseline (T0), immediate post-treatment (T1), and 4 weeks after the end of the 2 weeks of LT (T2). Sleep was measured by actigraphy. Blue-enriched LT had a significantly better effect on the Pittsburgh Sleep Quality Index at T2 compared to blue-attenuated LT, and a trend of better effectiveness on total sleep time at T2. There was a significant increase in Mini-Mental State Examination score at T2 after blue-enriched LT than that at T0. Our findings suggest that morning blue-enriched LT has a benefit in improving sleep and cognitive function in AD patients.

280 Is blue-enriched light more effective than red light to enhance vigilance and cognitive performance in Parkinson’s Disease?

Abstract Introduction Approximately 50% (between 16–74%) of adults with Parkinson’s disease (PD) show excessive daytime sleepiness. Besides its important role for vision, light conveys a powerful stimulating signal for alertness and cognition. Recent research has demonstrated that the blue part of light spectrum is the most efficient in enhancing vigilance and cognitive performance in young and older healthy individuals, thanks to a specific photoreception system within the eye which is particularly sensitive to blue wavelength. The aim of this pilot study was to compare the effects of blue-enriched light exposure (BL) and red-light placebo exposure (RL) on psychomotor vigilance and cognitive performance in adults with PD. Methods Sixteen participants with idiopathic PD (64.0±5.5 yrs, 6 women, Hoehn and Yahr status: 2) completed a brief neuropsychological assessment to exclude dementia, self-reported questionnaires and a complete eye examination in screening visits. The one-day experimental procedure included 1.25 h period of baseline dim-light exposition, followed by two light conditions presented in a counterbalanced design and separated by 15 minutes in dim-light: 1.25 h of BL at 959lux and 1.25 h of placebo RL condition at 472lux. Both light conditions were delivered by Luminette®. Data were normalized according to baseline dim-light evaluation. Mixed analyses of variance (2 light conditions X 2 orders) were performed to compare performance on an auditory psychomotor vigilance task (A-PVT) and an auditory 2-back cognitive tasks (A-2-back) during light exposure. Results We observed no significant effect of light conditions, orders and no interaction on reaction time (RT) and number of correct answers for the A-2-Back task. Furthermore, there was no significant difference between BL and RL on A-PVT performance including median RT, shift in optimum RT (i.e.,mean RT from fastest 10% RT), and duration of response in the lapse domain (i.e.,mean RT from slowest 10% RT). Conclusion These preliminary results do not support the notion that blue-enriched white light exposure is more efficient than red light exposure to stimulate psychomotor vigilance and cognitive performance in adults with PD. Next steps of analyses will compare the effects of BL and RL on subjective sleepiness and EEG cortical activation in the same population. Support (if any) CIHC &amp; QPN

The Effect of Blue-enriched White Light on Cognitive Performances and Sleepiness of Simulated Shift Workers: A Randomized Controlled Trial.

Shift work is associated with reduced performance and efficiency, the current study aimed at investigating whether blue-enriched white light could improve workers' performance. The study, which adopted a randomized controlled trial, was conducted among 48 simulated shift workers. The participants performed sustained attention task, working memory task, and sleepiness task during night shift work. The data was analyzed using two-way repeated measure ANOVA. The results indicated that, compared to conventional light, participants' correct responses of the sustained attention significantly increased when they were exposed to blue-enriched white light, correspondingly, the commission errors and omission errors declined. Furthermore, the blue-enriched white light had a significant effect on the decrease of sleepiness. However, the working memory was not significantly affected. Exposing to blue-enriched white light can improve sustained attention and reduce sleepiness.