Blue-Enriched Light Enhances Alertness but Impairs Accurate Performance in Evening Chronotypes Driving in the Morning

Attention maintenance is highly demanding and typically leads to vigilance decrement along time on task. Therefore, performance in tasks involving vigilance maintenance for long periods, such as driving, tends to deteriorate over time. Cognitive performance has been demonstrated to fluctuate over 24 h of the day (known as circadian oscillations), thus showing peaks and troughs depending on the time of day (leading to optimal and suboptimal times of day, respectively). Consequently, vigilance decrements are more pronounced along time on task when it is performed at suboptimal times of day. According to research, light exposure (especially blue-enriched white) enhances alertness. Thus, it has been proposed to prevent the vigilance decrement under such adverse circumstances. We aimed to explore the effects of blue-enriched white light (vs. dim light) on the performance of a simulated driving task at a suboptimal time of day. A group of evening-types was tested at 8 am, as this chronotype had previously shown their largest vigilance decrement at that time. In the dim light condition, vigilance decrements were expected on both subjective (as increments in the Karolinska Sleepiness Scale scores) and behavioral measures [as slower reaction times (RTs) in the auditory Psychomotor Vigilance Task, slower RTs to unexpected events during driving, and deteriorated driving accuracy along time on task]. Physiological activation was expected to decrease (as indexed by an increase of the distal-proximal temperature gradient, DPG). Under blue-enriched white light, all these trends should be attenuated. Results from the control dim light condition replicated the vigilance decrement in all measures. Most important, the blue-enriched white light attenuated this decrement, leading to both lower DPG and faster RTs. However, it impaired accuracy of driving performance, and did not have any effect on subjective sleepiness. We conclude that exposure to blue-enriched light provides an effective countermeasure to enhance vigilance performance at suboptimal times of day, according to measures such as RTs. However, it should be considered that alerting effects of light could impair accuracy in precision tasks as keeping a proper car position. The current findings provide ergonomic implications for safety and fatigue related management systems.This work was supported by the Spanish and Andalusian Governments to ÁC (MINECO: PSI2014-58041-P, and Proyectos de Excelencia JJAA: SEJ-3054) and to JM (MINECO: SAF2013- 49132-C2-1-R)

Randomized trial of polychromatic blue-enriched light for circadian phase shifting, melatonin suppression, and alerting responses.

Wavelength comparisons have indicated that circadian phase-shifting and enhancement of subjective and EEG-correlates of alertness have a higher sensitivity to short wavelength visible light. The aim of the current study was to test whether polychromatic light enriched in the blue portion of the spectrum (17,000 K) has increased efficacy for melatonin suppression, circadian phase-shifting, and alertness as compared to an equal photon density exposure to a standard white polychromatic light (4000 K). Twenty healthy participants were studied in a time-free environment for 7 days. The protocol included two baseline days followed by a 26-h constant routine (CR1) to assess initial circadian phase. Following CR1, participants were exposed to a full-field fluorescent light (1 × 10 14 photons/cm 2 /s, 4000 K or 17,000 K, n = 10/condition) for 6.5 h during the biological night. Following an 8 h recovery sleep, a second 30-h CR was performed. Melatonin suppression was assessed from the difference during the light exposure and the corresponding clock time 24 h earlier during CR1. Phase-shifts were calculated from the clock time difference in dim light melatonin onset time (DLMO) between CR1 and CR2. Blue-enriched light caused significantly greater suppression of melatonin than standard light ((mean ± SD) 70.9 ± 19.6% and 42.8 ± 29.1%, respectively, p \u3c 0.05). There was no significant difference in the magnitude of phase delay shifts. Blue-enriched light significantly improved subjective alertness (p \u3c 0.05) but no differences were found for objective alertness. These data contribute to the optimization of the short wavelength-enriched spectra and intensities needed for circadian, neuroendocrine and neurobehavioral regulation

Light-responsive expression atlas reveals the effects of light quality and intensity in Kalanchoë fedtschenkoi, a plant with crassulacean acid metabolism.

BackgroundCrassulacean acid metabolism (CAM), a specialized mode of photosynthesis, enables plant adaptation to water-limited environments and improves photosynthetic efficiency via an inorganic carbon-concentrating mechanism. Kalanchoë fedtschenkoi is an obligate CAM model featuring a relatively small genome and easy stable transformation. However, the molecular responses to light quality and intensity in CAM plants remain understudied.ResultsHere we present a genome-wide expression atlas of K. fedtschenkoi plants grown under 12 h/12 h photoperiod with different light quality (blue, red, far-red, white light) and intensity (0, 150, 440, and 1,000 μmol m-2 s-1) based on RNA sequencing performed for mature leaf samples collected at dawn (2 h before the light period) and dusk (2 h before the dark period). An eFP web browser was created for easy access of the gene expression data. Based on the expression atlas, we constructed a light-responsive co-expression network to reveal the potential regulatory relationships in K. fedtschenkoi. Measurements of leaf titratable acidity, soluble sugar, and starch turnover provided metabolic indicators of the magnitude of CAM under the different light treatments and were used to provide biological context for the expression dataset. Furthermore, CAM-related subnetworks were highlighted to showcase genes relevant to CAM pathway, circadian clock, and stomatal movement. In comparison with white light, monochrome blue/red/far-red light treatments repressed the expression of several CAM-related genes at dusk, along with a major reduction in acid accumulation. Increasing light intensity from an intermediate level (440 μmol m-2 s-1) of white light to a high light treatment (1,000 μmol m-2 s-1) increased expression of several genes involved in dark CO2 fixation and malate transport at dawn, along with an increase in organic acid accumulation.ConclusionsThis study provides a useful genomics resource for investigating the molecular mechanism underlying the light regulation of physiology and metabolism in CAM plants. Our results support the hypothesis that both light intensity and light quality can modulate the CAM pathway through regulation of CAM-related genes in K. fedtschenkoi

Сон в Антарктиде: от проблем с засыпанием до понимания проблем

From the fi rst expeditions, adaptation to the harsh environment of Antarctica, the expeditionists complained of a trouble sleeping. During a long stay on the continent, the polar explorers are exposed to a large number of extreme environmental factors both at the station and outside it, but the main physical factors of sleep disturbances are considered to be the peculiarities of light and photoperiod. Recently, more attention has been paid to clarifying the role of psychological adaptation to the Antarctica conditions, regarding the living in a small group and confi ned space. Existing methods to prevent the sleep disorders, fi rst of all, comprise the manipulating with light parameters, activity and rest schedules. A thorough preliminary selection of expeditionists to establish the necessary psychological climate, thinking about gender and multicultural characteristics of adaptation can also be considered with the perspective of preventive measures. At the same time, little attention is paid to the investigation of the role of ‘non-core’ factors (chronotype, personality traits and features of personal adaptation to the extreme environment of Antarctica), as well as forced contact with cold, affecting sleep.С первых экспедиций адаптация их участников к суровым условиям Антарктиды сопровождалась жалобами на нарушения сна. В ходе длительного пребывания на континенте полярники подвергаются воздействию большого количества экстремальных факторов окружающей среды как на станции, так и вне ее пределов, но основными физическими причинами, вызывающими нарушения сна, принято считать особенности освещенности и фотопериода. В последнее время более пристальное внимание уделяется выяснению роли психологической адаптации к условиям Антарктиды с учетом жизни в малой группе и замкнутом пространстве. Существующие методы противодействия нарушениям сна, в первую очередь, включают манипулирование параметрами освещенности, графиком работы и отдыха. Тщательный предварительный отбор участников для создания необходимого психологического климата, учет гендерных и мультикультурных особенностей адаптации также можно рассматривать с позиции превентивных мер. При этом изучению роли «неосновных» факторов (хронотип, личностные черты и особенности персональной адаптации к экстремальным условиям Антарктиды), а также вынужденного контакта с холодом, влияющих на сон, уделяется незначительное внимание

Contribution of time of day and the circadian clock to the heat stress responsive transcriptome in Arabidopsis.

In Arabidopsis, a large subset of heat responsive genes exhibits diurnal or circadian oscillations. However, to what extent the dimension of time and/or the circadian clock contribute to heat stress responses remains largely unknown. To determine the direct contribution of time of day and/or the clock to differential heat stress responses, we probed wild-type and mutants of the circadian clock genes CCA1, LHY, PRR7, and PRR9 following exposure to heat (37 °C) and moderate cold (10 °C) in the early morning (ZT1) and afternoon (ZT6). Thousands of genes were differentially expressed in response to temperature, time of day, and/or the clock mutation. Approximately 30% more genes were differentially expressed in the afternoon compared to the morning, and heat stress significantly perturbed the transcriptome. Of the DEGs (~3000) specifically responsive to heat stress, ~70% showed time of day (ZT1 or ZT6) occurrence of the transcriptional response. For the DEGs (~1400) that are shared between ZT1 and ZT6, we observed changes to the magnitude of the transcriptional response. In addition, ~2% of all DEGs showed differential responses to temperature stress in the clock mutants. The findings in this study highlight a significant role for time of day in the heat stress responsive transcriptome, and the clock through CCA1 and LHY, appears to have a more profound role than PRR7 and PRR9 in modulating heat stress responses during the day. Our results emphasize the importance of considering the dimension of time in studies on abiotic stress responses in Arabidopsis

Circadian regulation of glucose, lipid, and energy metabolism in humans.

The circadian system orchestrates metabolism in daily 24-hour cycles. Such rhythms organize metabolism by temporally separating opposing metabolic processes and by anticipating recurring feeding-fasting cycles to increase metabolic efficiency. Although animal studies demonstrate that the circadian system plays a pervasive role in regulating metabolism, it is unclear how, and to what degree, circadian research in rodents translates into humans. Here, we review evidence that the circadian system regulates glucose, lipid, and energy metabolism in humans. Using a range of experimental protocols, studies in humans report circadian rhythms in glucose, insulin, glucose tolerance, lipid levels, energy expenditure, and appetite. Several of these rhythms peak in the biological morning or around noon, implicating earlier in the daytime is optimal for food intake. Importantly, disruptions in these rhythms impair metabolism and influence the pathogenesis of metabolic diseases. We therefore also review evidence that circadian misalignment induced by mistimed light exposure, sleep, or food intake adversely affects metabolic health in humans. These interconnections among the circadian system, metabolism, and behavior underscore the importance of chronobiology for preventing and treating type 2 diabetes, obesity, and hyperlipidemia

The Recent History of Seasonal Affective Disorder (SAD)

Seminar TranscriptPsychiatric diagnosis is controversial and is regarded by some principally as a means of reinforcing the vested interests of medical professionals and pharmaceutical companies. On the other hand, the phenomena that are described in clinical psychiatric practice are real and clearly extend across time and between cultures. ‘In every culture there is some notion of emotional or psychological difference. Not all cultures identify these differences in the same way, nor do they use identical terms. Equally, however no culture is indifferent to those who are sad, frightened or unintelligible in their conduct.’ 1 The description and diagnosis of Seasonal Affective Disorder (SAD) or ‘winter depression’ is a comparatively recent development which provides an unrivalled opportunity to explore the construction of a psychopathological entity through the relevant peer-reviewed publications, as well as the professional and public reaction to these scientific discoveries. This Witness Seminar provides a riveting insight into the thinking of some key protagonists, both the scientists who developed the diagnosis of SAD as well as those for whom this new clinical entity resonated so clearly with their own experiences. What is the point of diagnosis? Ideally a diagnosis should point to a particular disease process, though even in general medicine this is often not the case. However, in a pragmatic sense the value of diagnosis is that it enables a group of people manifesting particular clinical phenomena to be identified as sharing a common prognosis and response to treatment – in the case of SAD a therapeutic response to artificial bright light. Indeed with SAD, it may be that increasing knowledge about the circadian effects of bright light stimulated a search for medical conditions in which it might be effective, that is, in some sense the availability of a treatment led to the identification of the condition. How truly recent is the identification of SAD as a diagnostic entity? In fact, seasonal variation in mood disorder has long been recognized and Rosenthal and colleagues (1984) quote the eminent nineteenth-century psychiatrist, Emil Kraepelin, as commenting in his standard textbook: ‘Repeatedly I saw in these cases moodiness set in in autumn and pass over in spring ... corresponding in a certain sense to the emotional changes which come over even healthy individuals at the changes of the seaso

Non-Visual Effects of Light on Melatonin, Alertness and Cognitive Performance: Can Blue-Enriched Light Keep Us Alert?

Light exposure can cascade numerous effects on the human circadian process via the non-imaging forming system, whose spectral relevance is highest in the short-wavelength range. Here we investigated if commercially available compact fluorescent lamps with different colour temperatures can impact on alertness and cognitive performance

Effects of light interventions for adaptation to night work : Simulated night work experiments

In modern society, the need for 24-hr operation and services requires some people to work outside normal daytime work hours (i.e. shift work), including the night. For instance, healthcare, police, and transportation, are sectors where night work is common. Exposure to shift work, and particularly night work, can have negative impact on the workers’ health. Especially, sleep is reported to be disturbed among night workers, as they must be awake at times they would normally be sleeping, and sleep at times they would normally be awake. This circadian misalignment of the sleep-wake rhythm may in a long-term perspective lead to ill health and diseases. Also, in a short-term perspective night work may cause adverse effects. Night workers experience increased sleepiness and performance deterioration during night shifts, and especially in the early morning hours, the sleep propensity and performance decrements are high. As such, night work has also been associated with increased risk of accidents and injuries. Several countermeasures to reduce the adverse impact of night work have been suggested. Common strategies involve scheduled naps and caffein use. However, there is increasing interest in the use of light interventions for eliciting beneficial effects for night workers. Light exposure has the potential to entrain the biological circadian rhythm in humans, and as such can be used to produce circadian adaptation to a night work schedule. In addition, light has acute alerting effects which can reduce alertness deficits and improve performance during the night shift. Such effects rely on several characteristics of the light, such as timing, intensity, and wavelengths (spectral distribution). With the development of light emitting diode (LED) technology, new strategies for illumination of workplaces have emerged. This thesis is based on three papers using standard ceiling mounted LED-luminaires to administer different light conditions during simulated night shift experiments. The main aim has been to investigate and elucidate how such LED lighting strategies can be used to facilitate adaptation to night work on measures of sleepiness, performance, and circadian rhythm. In paper 1, the objective was to investigate how a full spectrum (4000 K) bright light (~ 900 lx), compared to a standard light (~ 90 lx), affected alertness and performance during three consecutive simulated night shifts (23:00–07:00 hrs), as well as circadian phase shift after the simulated night shifts. Results indicated that bright light effectively reduces sleepiness, and improves performance during three consecutive night shifts, compared to standard light. Bright light seems to be beneficial in the later parts of the shifts, when sleep propensity is particularly high. For instance, in the later parts of night 2 and 3 it was found that the number of lapses of attention on a vigilance task revealed half as many lapses with bright light, compared to standard light. Furthermore, bright light induced a larger phase delay as compared with standard light, although data were incomplete, hence validation of these findings are needed. The objective in the second paper was to investigate how short-wavelength monochromatic blue light (λmax = 455 nm), compared to red light (λmax = 625 nm) with similar photon density (~ 2.8 x 1014 photons/cm2/s), affected alertness and task performance during one simulated night shift (23:00–06:45 hrs), as well as circadian phase shift following the night shift. The results in paper 2 suggest that monochromatic blue light reduces sleepiness and improves performance in the later parts of the night shift. Similar to the findings in paper 1, the number of attentional lapses with blue light was half of that seen with red light. Blue light also led to a larger phase delay of the circadian rhythm. There were indications of improved visual comfort with blue light, although both light conditions overall produced visual discomfort. In the third paper the main aims were to investigate how polychromatic blue-enriched white light (7000 K; ~ 200 lx), compared to warm white light (2500 K) of similar photon density (~ 1.6 x 1014 photons/cm2/s), affected alertness and performance during three consecutive simulated night shifts (23:00–06:45 hrs), as well as circadian adaptation to the night work schedule. The results indicated minor, yet beneficial effects of 7000 K light compared to 2500 K light, mainly in terms of fewer performance errors on a vigilance task in the end of night 1 and 2. No significant difference in terms of circadian phase shifts were found between these two light conditions. In conclusion, the papers suggest that standard ceiling mounted LED-luminaires have the potential to produce light conditions that may facilitate adaptation to night work. Paper 1 suggests that bright light improves performance and reduces sleepiness during three consecutive simulated night shifts. Results from paper 2 indicate that short-wavelength blue light improves performance, reduces sleepiness, and causes a larger phase delay than long-wavelength red light during one simulated night shift. Paper 3 indicates that using polychromatic blue-enriched white light has minor, yet beneficial effects on performance measures, compared to warm white light during three consecutive simulated night shifts. Further research is needed to validate and support the findings and investigate the impact and feasibility of similar light conditions in real-life workplaces. Future research should also explore more light conditions that can be favourable for night workers, in order to develop recommendations for illumination of night workers workplaces. Moreover, there is a need to elucidate potential long-term adverse health impacts of exposure to LED lighting.Doktorgradsavhandlin

Non-visual effects of light on human circadian physiology and neurobehavioral performance

Light is of crucial importance for human circadian rhythms. In fact, light exposure allows for resetting individual biological rhythms to the 24-h day. Besides its synchronizing effects, light also acts on different behavioural and physiological variables. The overarching aim of this thesis was to investigate the effect of different light properties, such as intensity, wavelength, duration, timing and dynamics, on neurobehavioral performance and circadian physiology, and possible inter-individual differences. In the first part, we investigated the effect of three morning light settings (dim light, DL < 8 lux; monochromatic blue light, mBL at 100 lux; and dawn simulation light, DsL increasing from 0 to 250 lux) in 17 young participants (20-35 years old), after two nights of 6-h sleep restriction, on alertness, well-being, melatonin and cortisol profiles and cognitive performance. We found that exposure to artificial morning DsL improved subjective perception of well-being and mood, as well as cognitive performance across the day compared to DL and mBL. Only morning mBL induced a phase advance of the circadian profile of melatonin, thus impacting on the circadian system. In the second part, we compared the effect of three light settings (dim light, DL <8 lux; polychromatic white light, WL at 250 lux; and blue- enriched polychromatic white light, BL at 250 lux) on subjective sleepiness and physiological variables during a 40-h sleep deprivation protocol. Inter-individual differences were investigated with respect to (1) age, by enrolling a cohort of 26 young (20-35 years old) and 12 older participants (55-75 years old); and (2) genetic predisposition (polymorphism in clock gene Period3), by enrolling 8 young PER34/4 and 8 young PER35/5 participants. Accordingly, the age-related effects were such that exposure to BL and WL improved subjective sleepiness in both age groups, while melatonin suppression was only detectable in the young, with a more pronounced effect under BL, and not in the older. Only the blue-enriched light modified cortisol levels, with a decrease in the young and an increase in the older. Both lights had a contrary effect depending on the age of the participant in regard to skin temperature and motor activity. With respect to the genetic predisposition, exposure to BL and WL suppressed melatonin in both groups, with a stronger effect under BL in the PER35/5. However, we showed a significant alerting response, a better well-being, and a decrease in cortisol levels only in the short allele carriers (PER34/4). In contrast, cognitive performance was decreased only in PER35/5 under WL. In conclusion, depending on the purpose to use non-visual effects of light, either DsL or mDL can be used to improve subjective mood and cognitive performance or to shift internal rhythms, respectively. In a broader perspective, the use of moderately bright light in night work and shift work settings, where constant light levels are very common, may differ across shift workers given their age and their genetic predisposition