Short-wavelength Light Exposure Research Articles

ICNIRP Statement on Short Wavelength Light Exposure from Indoor Artificial Sources and Human Health.

Concerns have been raised about the possibility of effects from exposure to short wavelength light (SWL), defined here as 380-550 nm, on human health. The spectral sensitivity of the human circadian timing system peaks at around 480 nm, much shorter than the peak sensitivity of daytime vision (i.e., 555 nm). Some experimental studies have demonstrated effects on the circadian timing system and on sleep from SWL exposure, especially when SWL exposure occurs in the evening or at night. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has identified a lack of consensus among public health officials regarding whether SWL from artificial sources disrupts circadian rhythm, and if so, whether SWL-disrupted circadian rhythm is associated with adverse health outcomes. Systematic reviews of studies designed to examine the effects of SWL on sleep and human health have shown conflicting results. There are many variables that can affect the outcome of these experimental studies. One of the main problems in earlier studies was the use of photometric quantities as a surrogate for SWL exposure. Additionally, the measurement of ambient light may not be an accurate measure of the amount of light impinging on the intrinsically photosensitive retinal ganglion cells, which are now known to play a major role in the human circadian timing system. Furthermore, epidemiological studies of long-term effects of chronic SWL exposure per se on human health are lacking. ICNIRP recommends that an analysis of data gaps be performed to delineate the types of studies needed, the parameters that should be addressed, and the methodology that should be applied in future studies so that a decision about the need for exposure guidelines can be made. In the meantime, ICNIRP supports some recommendations for how the quality of future studies might be improved.

Larval swimming in the sea anemone Nematostella vectensis is sensitive to a broad light spectrum and exhibits a wavelength-dependent behavioral switch.

In nearly all animals, light-sensing mediated by opsin visual pigments is important for survival and reproduction. Eyeless light-sensing systems, though vital for many animals, have received relatively less attention than forms with charismatic or complex eyes. Despite no single light-sensing organ, the sea anemone Nematostella vectensis has 29 opsin genes and multiple light-mediated behaviors throughout development and reproduction, suggesting a deceptively complex light-sensing system. To characterize one aspect of this light-sensing system, we analyzed larval swimming behavior at high wavelength resolution across the ultraviolet and visual spectrum. N. vectensis larvae respond to light at least from 315 to 650 nm, which is a broad sensitivity range even compared to many animals with complex eyes. Planktonic swimming is induced by ultraviolet (UV) and violet wavelengths until 420 nm. Between 420 and 430 nm a behavioral switch occurs where at wavelengths longer than 430 nm, larvae respond to light by swimming down. Swimming down toward the substrate is distinct from light avoidance, as animals do not exhibit positive or negative phototaxis at any wavelength tested. At wavelengths longer than 575 nm, animals in the water column take increasingly longer to respond and this behavior is more variable until 650 nm where larval response is no different from the dark, suggesting these longer wavelengths lie outside of their sensitivity range. Larval swimming is the only motile stage in the life history of N. vectensis, and increased planktonic swimming could lead to greater dispersal range in potentially damaging shallow environments with short-wavelength light exposure. Longer wavelength environments may indicate more suitable substrates for metamorphosis into the polyp stage, where the individual will remain for the rest of its life. Future work will test whether this robust behavior is mediated by multiple opsins.

Effect of hydroxychloroquine or chloroquine and short wavelength light on in vivo retinal function and structure in mouse eyes

ABSTRACT Clinical relevance The use of chloroquine or hydroxychloroquine can lead to both acute and chronic changes to both retinal structure and function. Background Chloroquine (CQ) and hydroxychloroquine (HCQ) have the potential for retina toxicity. The acute impact of short-term drug exposure (2-4 weeks) on in vivo retinal structure and function and assess whether short wavelength light exposure further exacerbates any structural and functional changes was assessed in a murine model. Methods Adult C57BL/6 J mice received intraperitoneal injection of vehicle or hydroxychloroquine (10 mg/kg) 3 times per week for 2 or 4 weeks, or chloroquine for 4 weeks (10 mg/kg). Over this period, animals were exposed to room light (8 hours) or short-wavelength light 4 hours per day (4 hours of normal room light) for 5 days each week. Retinal changes were assessed using electroretinography (ERG), in vivo optical coherence tomography (OCT) imaging. Results Short-term low-dose HCQ and CQ treatment led to RPE thickening and elongation of photoreceptors. These structural changes were associated with a no dysfunction in the case of HCQ treatments and widespread functional changes (photoreceptor sensitivity, bipolar cell amplitude and oscillatory potential amplitude) in the case of CQ treatment. Exposure to low intensity short-wavelength light does not appear to alter the effect of HCQ or CQ. Conclusions HCQ and CQ treatment has acute effects on both retinal structure and function, effects that were not exacerbated by short wavelength light exposure. Whether chronic short wavelength light exposure exacerbates these changes require further study.

Short-wavelength light exposure at night and sleep disturbances accompanied by decreased melatonin secretion in real-life settings: a cross-sectional study of the HEIJO-KYO cohort

ObjectivesTo determine the association between short-wavelength light exposure at night (LAN) power and sleep quality or melatonin levels in real-life settings. MethodsIn this cross-sectional study of 580 older adults (mean age, 71.0 years), we measured short-wavelength LAN power at cornea level using an originally developed light loggers over two nights. Sleep quality and physiological melatonin levels were measured using the Pittsburgh sleep quality index (PSQI) questionnaire and overnight urinary 6-sulfatoxymelatonin excretion (UME), respectively. ResultsThe first and second tertile short-wavelength LAN power values obtained were 0.77 × 10−2 μW/cm2 and 7.0 × 10−2 μW/cm2, respectively, and the overall prevalence of sleep disturbances was 34.7%. The mean UME was 1.88 ± 0.70 log μg. The mean global PSQI score and the prevalence of sleep disturbances significantly increased (P = 0.004 and 0.006, respectively) with increasing tertile groups of short-wavelength LAN power. In multivariable analysis adjusted for potential confounders, the odds ratio (OR) for sleep disturbances was significantly higher in the highest tertile group of short-wavelength LAN power compared with that in the lowest tertile group (adjusted OR, 1.90; 95% confidence interval [CI]: 1.20, 3.00; P = 0.006). In addition, UME was significantly lower in the highest tertile group of short-wavelength LAN power than that in the lowest tertile group (adjusted mean difference, −0.14 log μg; 95% CI: −0.28, −0.007; P = 0.039). ConclusionsAlthough short-wavelength LAN power measured at cornea level in real-life settings seemed to be significantly low, our findings suggest that short-wavelength LAN power is significantly associated with both melatonin levels and sleep disturbance.

How Smart Is It to Go to Bed with the Phone? The Impact of Short-Wavelength Light and Affective States on Sleep and Circadian Rhythms.

Previously, we presented our preliminary results (N = 14) investigating the effects of short-wavelength light from a smartphone during the evening on sleep and circadian rhythms (Höhn et al., 2021). Here, we now demonstrate our full sample (N = 33 men), where polysomnography and body temperature were recorded during three experimental nights and subjects read for 90 min on a smartphone with or without a filter or from a book. Cortisol, melatonin and affectivity were assessed before and after sleep. These results confirm our earlier findings, indicating reduced slow-wave-sleep and -activity in the first night quarter after reading on the smartphone without a filter. The same was true for the cortisol-awakening-response. Although subjective sleepiness was not affected, the evening melatonin increase was attenuated in both smartphone conditions. Accordingly, the distal-proximal skin temperature gradient increased less after short-wavelength light exposure than after reading a book. Interestingly, we could unravel within this full dataset that higher positive affectivity in the evening predicted better subjective but not objective sleep quality. Our results show disruptive consequences of short-wavelength light for sleep and circadian rhythmicity with a partially attenuating effect of blue-light filters. Furthermore, affective states influence subjective sleep quality and should be considered, whenever investigating sleep and circadian rhythms.

0172 Blue-Light Blockers and Sleep: A Meta-Analysis of Intervention Studies

Abstract Introduction Sleep and circadian physiology are influenced by external light, particularly within the short-wavelength portion of the visible spectrum (~450–480 nm). Most personal light-emitting electronic devices (e.g., tablets, smartphones, computers) are enriched in this so-called “blue” light. Interventions to reduce short-wavelength light exposure to the eyes before bedtime may help mitigate adverse effects of light-emitting electronic devices on sleep. Methods We conducted a meta-analysis of intervention studies on the effects of wearing color-tinted lenses (e.g., orange or amber) in frames in the evening before sleep to selectively filter short-wavelength light exposure to the eyes. Outcomes were self-reported or objective (wrist-accelerometer) measures of nocturnal sleep. Databases (MEDLINE, EMBASE, Cochrane Library, PsycINFO, CINAHL, AMED) were searched from inception to November 2019. PROSPERO Registration: CRD42018105854. Results Ten studies were identified (7 randomized controlled trials; 3 before-after studies). Findings of individual studies were inconsistent, with some showing benefit and others showing no effect of intervention. For objective sleep onset latency, there was a significant modest-sized combined effect (Hedge’s g=-0.52, 95% CI: -1.27-0.24, Z=-2.94, p=0.003, I2=16.6%, k=3). There was a minor but non-statistically significant combined effect for objective sleep efficiency (Hedge’s g=0.24, 95% CI: -0.16–0.64, Z=1.69, p=0.09, I2=23.7%, k=5). There were no significant combined effects for objective measures of total sleep time and wake after sleep onset. For self-reported total sleep time, there was a statistically significant medium-sized combined effect (Hedge’s g=0.61, 95% CI: 0.14–1.09, Z=5.56, p<0.01, I2=0%, k=3). Conclusion There is mixed evidence that this approach can improve sleep. Relatively few studies have been conducted, and most did not assess light levels or melatonin. The “blue-blocker” intervention may be particularly useful in individuals with insomnia, delayed sleep phase syndrome, or attention-deficit hyperactive disorder. Considering the ubiquitousness of short wavelength-enriched light sources and the potential for widespread sleep disturbance, future controlled studies examining the efficacy of this approach to improve sleep are warranted. Support N/A

Molecular pathological mechanism of blue ray induces murine photoreceptor cell 661W apoptosis

Modern life is full of artificial light in day and night. Smart phones, laptops, televisions, and high definition monitors provide unnatural human light source into human eye and cause ocular defects in modern human being. Understanding the molecular mechanism of the interplay between artificial light and ocular cells may help researcher society understanding the methods that preventing artificial light‐induced visual impairment. Here, we reported a short‐term exposure at short wavelength light source from blue and green light‐emitting diode (LED) could cause the murine photoreceptor cells 661W cells death, but not in red LED. However, the molecular mechanism remaining unclear. Using the molecular probe of caspase 3 reporter, we found the blue and green LED caused caspase 3 activation even as short as 10 minutes exposure and subsequently cell death at 16 hours later. We further confirmed 661W cells apoptosis by cleavage form caspase 3 and PARP formation. Moreover, we found the decreasing of mitochondria membrane potential and increasing of cellular relative‐oxygen species in 661W cells both indicate early cell apoptosis under short‐term exposure. Up to our knowledge, there was no transcriptome analysis which revealed immediately early gene expression in light‐induced cell death. Thus, we analyzed the 661W transcriptome at 2 hours after 10 minutes’ short wavelength light exposure and validated the candidate genes expression by RT‐Q‐PCR. Using the ingenuity pathway analysis, we found valuable up‐stream regulators, pathways, and potential mechanisms in short wavelength induced photoreceptor cell death and may provide novel therapy niches. In conclusion, our preliminary results prove that short wavelength light exposure can cause the photoreceptor cells death and the potential molecular clues. Further pathohistological analysis of key protein expression in the animal models may help us to prove the mechanism inside the eye damage from short wavelength light in future.Support or Funding InformationThis study was support by Shu Zen College of Medicine and Management with grant number (SZL10800012) and Academia Sinica

Interventions to reduce short-wavelength ("blue") light exposure at night and their effects on sleep: A systematic review and meta-analysis.

The sleep-wake and circadian cycles are influenced by light, particularly in the short-wavelength portion of the visible spectrum. Most personal light-emitting electronic devices are enriched in this so-called "blue" light. Exposure to these devices in the evening can disturb sleep. Interventions to reduce short-wavelength light exposure before bedtime may reduce adverse effects on sleep. We conducted a systematic review and meta-analysis to examine the effect of wearing color-tinted lenses (e.g. orange or amber) in frames to filter short-wavelength light exposure to the eye before nocturnal sleep. Outcomes were self-reported or objective measures of nocturnal sleep. Relatively few (k = 12) studies have been done. Study findings were inconsistent, with some showing benefit and others showing no effect of intervention. Meta-analyses yielded a small-to-medium magnitude combined effect size for sleep efficiency (Hedge's g = 0.31; 95% CI: -0.05, 0.66; I2 = 38.16%; k = 7), and a small-to-medium combined effect size for total sleep time (Hedge's g = 0.32; 95% CI: 0.01, 0.63; I2 = 12.07%; k = 6). For self-report measures, meta-analysis yielded a large magnitude combined effects size for Pittsburgh Sleep Quality Index ratings (Hedge's g = -1.25; 95% CI: -2.39, -0.11; I2 = 36.35%; k = 3) and a medium combined effect size for total sleep time (Hedge's g = 0.51; 95% CI: 0.18, 0.84; I2 = 0%; k = 3), Overall, there is some, albeit mixed, evidence that this approach can improve sleep, particularly in individuals with insomnia, bipolar disorder, delayed sleep phase syndrome, or attention-deficit hyperactive disorder. Considering the ubiquitousness of short-wavelength-enriched light sources, future controlled studies to examine the efficacy of this approach to improve sleep are warranted. Systematic review registration: PROSPERO 2018 CRD42018105854.

Filtration of Short-Wavelength Light Provides Therapeutic Benefit in Retinitis Pigmentosa Caused by a Common Rhodopsin Mutation.

The role of light exposure in accelerating retinitis pigmentosa (RP) remains controversial. Faster degeneration has however been observed in the inferior than superior retina in several forms ("sector" RP), including those caused by the rhodopsin P23H mutation, suggesting a modifying role of incident light exposure in such cases. Rearing of equivalent animal models in complete darkness has been shown to slow the degeneration. Here we investigate the use of red filters as a potential treatment strategy, with the hypothesis that minimizing retinal exposure to light <600 nm to which rods are maximally sensitive may provide therapeutic benefit. Knockin mice heterozygous for the P23H dominant rhodopsin mutation (RhoP23H/+) housed in red-tinted plastic cages were divided at weaning into either untinted or red-tinted cages. Subsequently, photoreceptor layer (PRL) thickness was measured by spectral-domain ocular coherence tomography, retinal function quantified by ERG, and cone morphology determined by immunohistochemical analysis (IHC) of retinal flatmounts. Mice remaining in red-tinted cages had a significantly greater PRL thickness than those housed in untinted cages at all time points. Red housing also led to a highly significant rescue of retinal function as determined by both dark- and light-adapted ERG responses. IHC further revealed a dramatic benefit on cone morphology and number in the red- as compared with the clear-housed group. Limitation of short-wavelength light exposure significantly slows degeneration in the RhoP23H/+ mouse model. Red filters may represent a cost-effective and low-risk treatment for patients with rod-cone dystrophy in whom a sectoral phenotype is noted.

Response to Letter to the Editor

To the Editor: Dr. Mortazavi brought up many important points regarding the effects of blue light and social networking on the sleep of young adults. Our previous works have reviewed the effects of short-wavelength light exposure on melatonin expression, circadian rhythms, and sleep patterns (1). In addition, the active use of technology and social networking on young adult sleep patterns has been well documented (2,3). The research on the effects of radiofrequency electromagnetic fields on sleep patterns is quite interesting and novel (4), and further research should be conducted to differentiate the specific effects of blue light and electromagnetic fields on circadian rhythms and sleep patterns. Given that the research is clear that exposure to technology can physiologically and psychologically impact a person’s sleep drive, we provided the standard recommendation that electronics should be avoided an hour before bedtime. Although the physiological effects of cellular phones are noteworthy, the overarching premise of the article “Technology as a Tool to Encourage Young Adult to Sleep and Eat Healthy” was to use technology in a way that enhances self-awareness of patterns of health and wellness. Because many young adults have difficulty placing boundaries on technology use, standard behavioral health recommendations, such as turning off the phone an hour before bed, tend to be difficult to achieve. Therefore, using apps such as SleepBot may work toward maximizing sleep duration, efficiency, and self-awareness of sleep patterns. It should be noted that if SleepBot is used to track sleep, individuals would benefit from using the built-in dimming feature to dim the screen display, using the blue light filter currently built into many smartphones, or turning the screen face down on the surface to minimize exposure to light. These steps would help to minimize the negative effects of blue light on sleep. It seems that the only strategy to minimize exposure to electromagnetic fields would be to turn off the phone, but as mentioned earlier, this is easier said than done in young adults whose need for social inclusion often outweighs the need for optimal sleep health. Sue K. Adams, Ph.D., Department of Human Development and Family Studies, University of Rhode Island, Transition Center, Rm 208, 55 Lower College Rd, Kingston, RI 02881 E-mail: [email protected] Gary Liguori, Ph.D., FACSM, Dean, College of Health Sciences, Co-Director, Academic Health Collaborative, Professor of Kinesiology, 106 Quinn Hall, 55 Lower College Rd, University of Rhode Island, Kingston, RI 02881 E-mail: [email protected] Ingrid E. Lofgren, Ph.D., M.P.H., R.D., Nutrition and Food Sciences, College of Health Sciences, University of Rhode Island, 144B Fogarty Hall, 55 Lower College Rd, Kingston, RI 02881 E-mail: [email protected]

Differential effect of long versus short wavelength light exposure on pupillary re‐dilation in patients with outer retinal disease

In patients with outer retinal degeneration, a differential pupil response to long wavelength (red) versus short wavelength (blue) light stimulation has been previously observed. The goal of this study was to quantify differences in the pupillary re-dilation following exposure to red versus blue light in patients with outer retinal disease and compare them with patients with optic neuropathy and with healthy subjects. Prospective comparative cohort study. Twenty-three patients with outer retinal disease, 13 patients with optic neuropathy and 14 normal subjects. Subjects were tested using continuous red and blue light stimulation at three intensities (1, 10 and 100 cd/m2) for 13 s per intensity. Pupillary re-dilation dynamics following the brightest intensity was analysed and compared between the three groups. The parameters of pupil re-dilation used in this study were: time to recover 90% of baseline size; mean pupil size at early and late phases of re-dilation; and differential re-dilation time for blue versus red light. Patients with outer retinal disease showed a pupil that tended to stay smaller after light termination and thus had a longer time to recovery. The differential re-dilation time was significantly greater in patients with outer retinal disease (median = 28.0 s, P < 0.0001) compared with controls and patients with optic neuropathy. A differential response of pupil re-dilation following red versus blue light stimulation is present in patients with outer retinal disease but is not found in normal eyes or among patients with visual loss from optic neuropathy.

Implications of controlled short-wavelength light exposure for sleep in older adults

BackgroundEnvironmental and physiological conditions make older adults more likely to lose synchronization to their local time and experience sleep disturbances. A regular, 24-hour light/dark cycle promotes synchronization. It is now well established that the circadian system is maximally sensitive to short-wavelength (blue) light. The purpose of the present study was to measure dose effectiveness (amounts and durations) of short-wavelength (blue) light for stimulating the circadian systems of older adults. We investigated the impact of six corneal irradiances (0.7 to 72 μW/cm2) of 470-nm light on nocturnal melatonin production. Nine participants, each over 50 years of age completed a within-subjects study. Each week, participants were exposed to one of the six irradiances of 470-nm light for 90 minutes.FindingsA two-factor (6 corneal irradiances × 10 exposure durations), within-subjects analysis of variance (ANOVA) was conducted using the melatonin suppression levels. The ANOVA revealed a significant main effect of corneal irradiance (F5, 30 = 9.131, p < 0.0001), a significant main effect of exposure duration (F9, 54 = 5.731, p < 0.0001), and a significant interaction between these two variables (F45,270 = 1.927, p < 0.001). Post hoc t-tests revealed that corneal irradiances as low as 2 μW/cm2 reliably suppressed melatonin after 90-minute exposure whereas 0.7 μW/cm2 did not.ConclusionsSleep disorders are common and a serious problem for millions of older adults. The present results showed that comfortable, precise and effective doses of light can be prescribed to older adults to reliably stimulate the circadian system that presumably would promote entrainment and, thus, regular sleep. Field studies on the impact of short-wavelength-light doses on sleep efficiency in older adults should be performed.

Effects of an advanced sleep schedule and morning short wavelength light exposure on circadian phase in young adults with late sleep schedules

We examined the effects of an advanced sleep/wake schedule and morning short wavelength (blue) light in 25 adults (mean age±SD=21.8±3 years; 13 women) with late sleep schedules and subclinical features of delayed sleep phase disorder (DSPD). After a baseline week, participants kept individualized, fixed, advanced 7.5-h sleep schedules for 6days. Participants were randomly assigned to groups to receive "blue" (470nm, ∼225lux, n=12) or "dim" (<1lux, n=13) light for 1h after waking each day. Head-worn "Daysimeters" measured light exposure; actigraphs and sleep diaries confirmed schedule compliance. Salivary dim light melatonin onset (DLMO), self-reported sleep, and mood were examined with 2×2 ANOVA. After 6days, both groups showed significant circadian phase advances, but morning blue light was not associated with larger phase shifts than dim-light exposure. The average DLMO advances (mean±SD) were 1.5±1.1h in the dim light group and 1.4±0.7h in the blue light group. Adherence to a fixed advanced sleep/wake schedule resulted in significant circadian phase shifts in young adults with subclinical DSPD with or without morning blue light exposure. Light/dark exposures associated with fixed early sleep schedules are sufficient to advance circadian phase in young adults.

Measuring circadian light and its impact on adolescents

A field study was conducted with eighth-grade students to determine the impact of morning light on circadian timing, sleep duration and performance. Before and during school hours for a week in February 2009, half the students studied wore orange glasses that minimized short-wavelength light exposure needed for circadian system stimulation. A control group did not wear the orange glasses. The Daysimeter, a circadian light meter, measured light/dark exposures in both groups for seven days. Circadian timing was significantly delayed for those students who wore orange glasses compared to the control group. Sleep durations were slightly, but not significantly, curtailed in the orange-glasses group. Performance scores on a brief, standardized psychomotor vigilance test and self-reports of well-being were not significantly different between the two groups.

Blue light–filtering intraocular lenses: Review of potential benefits and side effects

Blue light-filtering intraocular lenses (IOLs) have become part of the modern cataract surgeon's armamentarium and are widely used. Their advocates suggest they may protect against light-induced retinal damage and also affect the development or progression of age-related macular degeneration. Much of the evidence for photoprotection is theoretical or based on observations in cell culture or animal experiments, with little clinical information to date. Although arguments remain theoretical, there is now emerging clinical data on the use of these IOLs in patients looking at the benefits and potential side effects. In this review, we consider the background to the development of these IOLs, the evidence for a reduction in short-wavelength light exposure protecting retinal cells and function, and the possible disadvantages of IOLs resulting from their reduced light transmission. We place this information in context with regard to patients having cataract surgery and the day-to-day conditions in which they live.

Does Melanopsin Bistability Have Physiological Consequences?

Recent publications in the Journal of Biological Rhythms have focused on the hypothesis that the property of melanopsin bistability is functionally translated to in vivo mammalian physiology. Physiological consequences of photopigment bistability likely can be inferred from the more extensive invertebrate literature. In invertebrates, photopigment bistability results in (a) photoreceptor independence from specialized chromophore regenerating systems, (b) long-wavelength enhancement of a blue light effect, (c) expression of a prolonged depolarization after potential following intense blue light stimulation,and (d) photopigment endocytosis following chronic short-wavelength light exposure. If analogous physiological phenomena result from melanopsin bistability in mammals, then one can take advantage of the spectral composition of a light source to modulate its impact on photoentrainment and other light-dependent circadian phenomena. In any event,investigators studying phenomena that are affected by photic stimulation of intrinsically photosensitive retinal ganglion cells should detail the spectral composition of their light sources before, during, and after an experimental photic stimulus.