Role of nocturnal light intensity on adaptation to three consecutive night shifts: a counterbalanced crossover study

2020 ◽  
Vol 77 (4) ◽  
pp. 249-255 ◽  
Author(s):  
Erlend Sunde ◽  
Jelena Mrdalj ◽  
Torhild Pedersen ◽  
Eirunn Thun ◽  
Bjørn Bjorvatn ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Bright Light ◽  
Vigilance Task ◽  
Night Work ◽  
Digit Symbol Substitution Test ◽  
Consecutive Night ◽  
Full Spectrum ◽  
Improved Performance ◽  
Subjective Alertness ◽  
Night Shifts

ObjectivesTo investigate how a standard ceiling mounted light-emitting diode (LED)-based bright light intervention affected alertness and neurobehavioural performance during three consecutive simulated night shifts, and timing of circadian rhythm after the shifts.MethodsTwenty seven participants (20 females, 21.4±2.1 years; mean±SD) worked three consecutive night shifts (23:00–07:00) under a full-spectrum (4000 K) bright light (900 lx) and a standard light (90 lx) condition in a counterbalanced crossover design (separated by 4 weeks). Subjective alertness (Karolinska Sleepiness Scale) and neurobehavioural performance (Psychomotor Vigilance Task and Digit Symbol Substitution Test) were assessed five times during each shift. Salivary dim-light melatonin onset (DLMO) was assessed before and after the shifts. The simulated night shifts were conducted in a laboratory while the participants slept at home.ResultsSubjective alertness and neurobehavioural performance deteriorated during the night shifts in both light conditions. However, bright light significantly reduced alertness and performance decrements as compared with standard light. For a subset of the participants, DLMO was delayed by a mean of 3:17±0:23 (mean±SEM) hours after three night shifts in bright light and by 2:06±0:15 hours in standard light, indicating that bright light causes larger phase delay.ConclusionBright light improved performance and alertness during simulated night shifts and improved adaptation to night work. Bright light administered by ceiling mounted LED luminaires has the potential to improve adaptation to night work and reduce the risk of accidents and injuries among night workers.Trial registration numberNCT03203538.

Efficacy of bright light and sleep/darkness scheduling in alleviating circadian maladaptation to night work

2001 ◽  
Vol 281 (2) ◽  
pp. E384-E391 ◽  
Author(s):  
Todd S. Horowitz ◽  
Brian E. Cade ◽  
Jeremy M. Wolfe ◽  
Charles A. Czeisler
Keyword(s):  
Shift Work ◽  
Night Shift ◽  
Bright Light ◽  
Night Work ◽  
Sleep Episode ◽  
Work Related ◽  
Before And After ◽  
Dim Light ◽  
Night Shifts ◽  
Better Than

We tested the hypothesis that circadian adaptation to night work is best achieved by combining bright light during the night shift and scheduled sleep in darkness. Fifty-four subjects participated in a shift work simulation of 4 day and 3 night shifts followed by a 38-h constant routine (CR). Subjects received 2,500 lux ( Bright Light) or 150 lux ( Room Light) during night shifts and were scheduled to sleep (at home in darkened bedrooms) from 0800 to 1600 ( Fixed Sleep) or ad libitum ( Free Sleep). Dim light melatonin onset (DLMO) was measured before and after the night shifts. Both Fixed Sleepand Bright Light conditions significantly phase delayed DLMO. Treatments combined additively, with light leading to larger phase shifts. Free Sleep subjects who spontaneously adopted consistent sleep schedules adapted better than those who did not. Neither properly timed bright light nor fixed sleep schedules were consistently sufficient to shift the melatonin rhythm completely into the sleep episode. Scheduling of sleep/darkness should play a major role in prescriptions for overcoming shift work-related phase misalignment.

Intermittent bright light and exercise to entrain human circadian rhythms to night work

1999 ◽  
Vol 277 (6) ◽  
pp. R1598-R1604 ◽  
Author(s):  
Erin K. Baehr ◽  
Louis F. Fogg ◽  
Charmane I. Eastman
Keyword(s):  
Circadian Rhythms ◽  
Intermittent Exercise ◽  
Bright Light ◽  
Phase Shifts ◽  
Night Work ◽  
Temperature Minimum ◽  
Daytime Sleep ◽  
Human Circadian Rhythms ◽  
Dim Light ◽  
Night Shifts

Bright light can phase shift human circadian rhythms, and recent studies have suggested that exercise can also produce phase shifts in humans. However, few studies have examined the phase-shifting effects of intermittent bright light, exercise, or the combination. This simulated night work field study included eight consecutive night shifts followed by daytime sleep/dark periods (delayed 9 h from baseline). There were 33 subjects in a 2 × 2 design that compared 1) intermittent bright light (6 pulses, 40-min long each, at 5,000 lx) versus dim light and 2) intermittent exercise (6 bouts, 15-min long each, at 50–60% of maximum heart rate) versus no exercise. Bright light and exercise occurred during the first 6 h of the first three night shifts. The circadian phase marker was the demasked rectal temperature minimum. Intermittent bright-light groups had significantly larger phase delays than dim-light groups, and 94% of subjects who received bright light had phase shifts large enough for the temperature minimum to reach daytime sleep. Exercise did not affect phase shifts; neither facilitating nor inhibiting phase shifts produced by bright light.

098 Effects of Metameric Display-Light on Alertness, Vigilance and Melatonin

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A40-A41
Author(s):  
Isabel Schöllhorn ◽  
Oliver Stefani ◽  
Manuel Spitschan ◽  
Robert Lucas ◽  
Christian Cajochen
Keyword(s):  
Statistical Power ◽  
Light Exposure ◽  
Vigilance Task ◽  
Ongoing Study ◽  
Swiss National Science Foundation ◽  
Visual Appearance ◽  
Salivary Melatonin ◽  
Subjective Alertness ◽  
Psychomotor Vigilance ◽  
Circadian Physiology

Abstract Introduction Light emitted from visual displays can acutely increase alertness, improve cognitive performance and suppress melatonin in the evening. Here we tested the influence of different melanopic irradiance levels emitted by a metameric display setting on alertness, vigilance and salivary melatonin levels. Methods In an ongoing study, 37 healthy, male participants have so far completed a 2-week study protocol. Volunteers were assigned to one of four luminance groups which differed in brightness levels (27 cd/m2 - 280 cd/m2). Illuminance ranged between 7 and 85 lx. Within the four groups each volunteer was exposed to a low melanopic (LM) and a high melanopic condition (HM). The LM and HM differed in melanopic irradiance (ca. 3-fold change), but matched in terms of cone excitation (metamers). Before, during and after the light exposure, volunteers performed a psychomotor vigilance task (PVT). Subjective alertness and melatonin levels were continuously measured in half-hourly intervals throughout scheduled wakefulness in the 17-h in lab study. Results Preliminary analysis yielded an overall alerting response in the HM vs. the LM condition (p<0.05) concomitant with a trend of reduced melatonin levels in HM vs. LM (p=0.08). So far, we could not observe a difference in PVT performance for HM and LM (Reaction time responses between 100 and 500 ms). Since we are still lacking statistical power in the ongoing study, we cannot yet satisfactorily interpret interaction effects between melanopic condition and brightness. Conclusion Our data indicate that rather low brightness levels of high melanopic display light impacts alertness and melatonin levels in the evening. Thus, metameric low melanopic display light may be a promising method to attenuate activating properties of evening light on circadian physiology without affecting visual appearance. Support (if any) This project is funded by the Swiss National Science Foundation (SNSF).

scholarly journals Chronotype-specific Sleep in Two Versus Four Consecutive Shifts

2021 ◽  
pp. 074873042110060
Author(s):  
Dorothee Fischer ◽  
Till Roenneberg ◽  
Céline Vetter
Keyword(s):  
Night Shift ◽  
Sleep Diary ◽  
Sequence Length ◽  
Consecutive Night ◽  
Shift Workers ◽  
Subject Field ◽  
Sleep Diaries ◽  
Social Jetlag ◽  
Sleep Debt ◽  
Night Shifts

The study aimed to explore chronotype-specific effects of two versus four consecutive morning or night shifts on sleep-wake behavior. Sleep debt and social jetlag (a behavioral proxy of circadian misalignment) were estimated from sleep diary data collected for 5 weeks in a within-subject field study of 30 rotating night shift workers (29.9 ± 7.3 years, 60% female). Mixed models were used to examine whether effects of shift sequence length on sleep are dependent on chronotype, testing the interaction between sequence length (two vs. four) and chronotype (determined from sleep diaries). Analyses of two versus four morning shifts showed no significant interaction effects with chronotype. In contrast, increasing the number of night shifts from two to four increased sleep debt in early chronotypes, but decreased sleep debt in late types, with no change in intermediate ones. In early types, the higher sleep debt was due to accumulated sleep loss over four night shifts. In late types, sleep duration did not increase over the course of four night shifts, so that adaptation is unlikely to explain the observed lower sleep debt. Late types instead had increased sleep debt after two night shifts, which was carried over from two preceding morning shifts in this schedule. Including naps did not change the findings. Social jetlag was unaffected by the number of consecutive night shifts. Our results suggest that consecutive night shifts should be limited in early types. For other chronotypes, working four night shifts might be a beneficial alternative to working two morning and two night shifts. Studies should record shift sequences in rotating schedules.

scholarly journals Effect of shift work on fatigue and sleep in neonatal registrars

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245428
Author(s):  
Ajay P. Anvekar ◽  
Elizabeth A. Nathan ◽  
Dorota A. Doherty ◽  
Sanjay K. Patole
Keyword(s):  
Reaction Time ◽  
Vigilance Task ◽  
Sleep Diary ◽  
Secondary Outcome ◽  
Subjective Sleepiness ◽  
Working Day ◽  
Psychomotor Vigilance ◽  
Night Shifts ◽  
Mean Reaction Time

Objective We aimed to study fatigue and sleep in registrars working 12-hour rotating shifts in our tertiary neonatal intensive unit. Methods and participants This study involved neonatal registrar’s working day (08:00–21:00) and night (20:30–08:30) shifts. Participants maintained a sleep diary, answered a self-reported sleepiness questionnaire assessing subjective sleepiness, and performed a 10-minute psychomotor vigilance task (PVT) at the start and end of each shift. Primary outcomes: (1) Fatigue at the (i) “start vs end” of day and night shifts, (ii) end of the “day vs night” shifts, and (iii) end of “first vs last shift” in block of day and night shifts. (2) Duration and quality of sleep before the “day vs night” shifts. Mean reaction time (RTM), relative coefficient of variation (RTCV), and lapses (reaction time > 500ms) were used as measures of fatigue on PVT. Secondary outcome: Subjective sleepiness (self-reported sleepiness questionnaire) at the ‘start vs end” of day and night shifts. Results Fifteen registrars completed the study. Acuity was comparable for all shifts. (1) Psychomotor responses were impaired at the end vs start of day shifts [RTM (p = 0.014), lapses (p = 0.001)], end vs start of night shifts [RTM (p = 0.007), RTCV (p = 0.003), lapses (p<0.001)] and end of night vs day shifts [RTM (p = 0.007), RTCV (p = 0.046), lapses (p = 0.001)]. Only lapses were significantly increased at the end of the last (p = 0.013) vs first shift (p = 0.009) in a block of day and night shifts. (2) Duration of sleep before the night (p = 0.019) and consecutive night shifts was decreased significantly (p = 0.034). Subjective sleepiness worsened after day (p = 0.014) and night shifts (p<0.001). Conclusion Fatigue worsened after the 12-hour day and night shifts with a greater change after night shifts. Lapses increased after block of day and night shifts. Sleep was decreased before night shifts. Our findings need to be confirmed in larger studies.

Conflicting Bright Light Exposure during Night Shifts Impedes Circadian Adaptation

1997 ◽  
Vol 12 (1) ◽  
pp. 5-15 ◽  
Author(s):  
Paula J. Mitchell ◽  
Erin K. Hoese ◽  
Liwen Liu ◽  
Louis F. Fogg ◽  
Charmane I. Eastman
Keyword(s):  
Light Exposure ◽  
Bright Light ◽  
Bright Light Exposure ◽  
Night Shifts

N-face GaN substrate roughening for improved performance GaN-on-GaN LED

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ezzah Azimah Alias ◽  
Muhammad Esmed Alif Samsudin ◽  
Steven DenBaars ◽  
James Speck ◽  
Shuji Nakamura ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Light Emitting Diode ◽  
Optical Power ◽  
Ammonium Hydroxide ◽  
Content Type ◽  
Light Emitting ◽  
Gan Led ◽  
Improved Performance ◽  
Substrate Roughening

Purpose This study aims to focus on roughening N-face (backside) GaN substrate prior to GaN-on-GaN light-emitting diode (LED) growth as an attempt to improve the LED performance. Design/methodology/approach The N-face of GaN substrate was roughened by three different etchants; ammonium hydroxide (NH4OH), a mixture of NH4OH and H2O2 (NH4OH: H2O2) and potassium hydroxide (KOH). Hexagonal pyramids were successfully formed on the surface when the substrate was subjected to the etching in all cases. Findings Under 30 min of etching, the highest density of pyramids was obtained by NH4OH: H2O2 etching, which was 5 × 109 cm–2. The density by KOH and NH4OH etchings was 3.6 × 109 and 5 × 108 cm–2, respectively. At standard operation of current density at 20 A/cm2, the optical power and external quantum efficiency of the LED on the roughened GaN substrate by NH4OH: H2O2 were 12.3 mW and 22%, respectively, which are higher than its counterparts. Originality/value This study demonstrated NH4OH: H2O2 is a new etchant for roughening the N-face GaN substrate. The results showed that such etchant increased the density of the pyramids on the N-face GaN substrate, which subsequently resulted in higher optical power and external quantum efficiency to the LED as compared to KOH and NH4OH.

Automated Precision Assembly for High-Volume HB LEDs

2011 ◽  
Vol 2011 (1) ◽  
pp. 000117-000122
Author(s):  
Donald J. Beck ◽  
Jessica Sylvester
Keyword(s):  
Light Emitting Diode ◽  
High Reliability ◽  
Bright Light ◽  
High Volume ◽  
Commercial Production ◽  
Production Lines ◽  
Light Emitting ◽  
Die Attach ◽  
High Volume Production ◽  
Volume Production

Since the introduction of automated die and wire bonders in the 1980s, equipment manufacturers and process engineers have been challenged to balance speed with repeatability. Today, die bonders can perform epoxy die attach at a rate of 1.5 to 4 thousand die per hour [6]; and wire bonders can interconnect complex packages at speeds of more than 10 wires per second [7]. The advantage of automation is speed and consistency—however, there is one major concern with operating at these speeds: if something in the assembly process is wrong, everything will be wrong. Having tightly regulated assembly processes helps avoid the risk of building a large batch of rejected product. This paper presents a methodology and process flow supporting High Bright Light Emitting Diode (HB LED) automated assembly, supported by equipment certification, product inspection and SPC data collection methods. The methods presented in this paper have been formulated through extensive work in the high-reliability microelectronics industry and commercial production lines over the last three decades. To ensure time-to-market success in high-volume production, specific methods to achieve throughput and quality are required. This paper will cover the strategies and methods necessary to achieve the ultimate goal of an automated precision HB LED assembly—to blend the requirements of high-reliability and high-throughput to support high-volume commercial production.

0097 Effects of Experimental Sleep Disruption on Morning Cognitive Performance and Alertness

SLEEP ◽  
2020 ◽  
Vol 43 (Supplement_1) ◽  
pp. A39-A39
Author(s):  
E D Chinoy ◽  
D A Hirsch ◽  
J A Cuellar ◽  
M N Snider ◽  
T L Dunn ◽  
...  
Keyword(s):  
Cognitive Performance ◽  
Vigilance Task ◽  
Performance Outcomes ◽  
Cognitive Test ◽  
Sleep Disruption ◽  
Naval Research ◽  
Negative Effects ◽  
Percent Correct ◽  
Time In Bed ◽  
Subjective Alertness

Abstract Introduction While sleep duration is known to affect next-day cognitive performance and alertness, largely in a dose-response manner, the effects of disrupted sleep (where one is awoken multiple times overnight, common in military settings) are much less understood. Therefore, we examined the effects of experimentally disrupted sleep on morning cognitive performance and alertness. Methods We tested 34 healthy participants (12 men, 22 women, 28.1±3.9 years; mean±SD) who slept for 8-hours time-in-bed on three consecutive nights with polysomnography in a controlled sleep lab. The final two nights were randomized and counterbalanced between an undisrupted and a disrupted sleep condition. On the disrupted sleep night, participants were awoken by auditory tones for a 5–10 min period every hour. The following morning, participants completed a cognitive test battery that included Karolinska Sleepiness Scale (KSS), 10-min psychomotor vigilance task (PVT), addition calculations (ADD), go/no-go (GNG), task switching (TS), and working memory (WM). Mixed effects models were used to test factors: condition (undisrupted vs. disrupted), condition-order, and their interaction. Results Significant (p&lt;0.05) effects of condition (i.e., disrupted sleep caused worse performance) were found for PVT reaction time (RT), GNG RT, TS RT, WM percent correct, and KSS alertness ratings. Condition was not significant for number or percent correct on ADD, GNG, and TS. Condition-order was significant for TS percent correct, and significant interactions were found for ADD number correct and TS RT. Conclusion One night of sleep disruption caused significant negative effects on morning subjective alertness and on several, but not all, cognitive performance domains tested, including RT and WM. Condition-order and interaction effects were also found, indicating that some performance outcomes were impacted by possible learning effects over the study. Sleep disruption factors should be taken into account, especially in operational settings like the military where environmental factors (e.g., noise) disrupt sleeping conditions. Support Office of Naval Research, Code 34

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