ArticlePDF Available

Lack of short-wavelength light during the school day delays dim light melatonin onset (DLMO) in middle school students

Authors:

Abstract and Figures

Circadian timing affects sleep onset. Delayed sleep onset can reduce sleep duration in adolescents required to awake early for a fixed school schedule. The absence of short-wavelength ("blue") morning light, which helps entrain the circadian system, can hypothetically delay sleep onset and decrease sleep duration in adolescents. The goal of this study was to investigate whether removal of short-wavelength light during the morning hours delayed the onset of melatonin in young adults. Dim light melatonin onset (DLMO) was measured in eleven 8th-grade students before and after wearing orange glasses, which removed short-wavelength light, for a five-day school week. DLMO was significantly delayed (30 minutes) after the five-day intervention, demonstrating that short-wavelength light exposure during the day can be important for advancing circadian rhythms in students. Lack of short-wavelength light in the morning has been shown to delay the circadian clock in controlled laboratory conditions. The results presented here are the first to show, outside laboratory conditions, that removal of short-wavelength light in the morning hours can delay DLMO in 8th-grade students. These field data, consistent with results from controlled laboratory studies, are directly relevant to lighting practice in schools.
Content may be subject to copyright.
To cite this article:
Neuroendocrinol Lett 2010; 31(1):92–96
ORIGINAL ARTICLE
Neuroendocrinology Letters Volume 31 No. 1 2010
Lack of short-wavelength light during the
school day delays dim light melatonin
onset (DLMO) in middle school students
Mariana G. F and Mark S. R
Lighting Research Center, Rensselaer Polytechnic Institute, Troy, New York, USA
Correspondence to: Mariana Figueiro
Lighting Research Center
21 Union St., Troy, NY 12180, USA.
: +1 (518) 687-7100; : +1 (518) 687-7120; -: figuem@rpi.edu
Submitted: 2009-10-21 Accepted: 2009-12-15 Published online: 2010-02-16
Key words: daylight; melatonin; circadian system; adolescents; sleep
Neuroendocrinol Lett 2010; 31(1):92–96 PMID: 20150866 NEL310110A04 © 2010 Neuroendocrinology Letters ww w.nel.edu
Abstract
OBJECT IVE: Circadian timing affects sleep onset. Delayed sleep onset can reduce
sleep duration in adolescents required to awake early for a fixed school schedule.
The absence of short-wavelength (“blue”) morning light, which helps entrain the
circadian system, can hypothetically delay sleep onset and decrease sleep dura-
tion in adolescents. The goal of this study was to investigate whether removal of
short-wavelength light during the morning hours delayed the onset of melatonin
in young adults.
METHOD S: Dim light melatonin onset (DLMO) was measured in eleven 8th-grade
students before and after wearing orange glasses, which removed short-wavelength
light, for a five-day school week.
RESULTS : DLMO was significantly delayed (30 minutes) after the five-day inter-
vention, demonstrating that short-wavelength light exposure during the day can
be important for advancing circadian rhythms in students.
CONCLUS IONS: Lack of short-wavelength light in the morning has been shown
to delay the circadian clock in controlled laboratory conditions. The results
presented here are the first to show, outside laboratory conditions, that removal
of short-wavelength light in the morning hours can delay DLMO in 8th-grade
students. These field data, consistent with results from controlled laboratory stud-
ies, are directly relevant to lighting practice in schools.
INTRODUCTION
In terrestrial mammals, circadian rhythms are
regulated by the interaction of the internal bio-
logical clock located in the suprachiasmatic nuclei
(SCN) of the hypothalamus with the earth’s natu-
ral 24-hour light-dark pattern (Refinetti 2006).
The SCN are self-sustaining oscillators with an
intrinsic period that is typically slightly longer or
shorter than 24 hours. The timing of the SCN is
set by the local light-dark pattern, usually ensur-
ing that the organism’s behavioral and physiologi-
cal rhythms are synchronized with its photic niche
(nocturnal, diurnal, or crepuscular).
Light incident on human retinas will entrain or
phase shift SCN timing, depending upon the time,
duration, spectrum and intensity of the stimulus
(Stevens & Rea 2001). These fundamental light
93
Neuroendocrinology Letters Vol. 31 No. 1 2010 • Article available online: http://node.nel.edu
Lack of short-wavelength light during the school day delays dim light melatonin onset
characteristics affect the circadian system differently
than they affect the visual system. Although we now
know the human circadian system is more sensitive to
light than was originally thought (Lewy et al. 1980), it is
much less sensitive to light than the visual system (Rea
et al. 2002). It is also well established that the human
circadian system is maximally sensitive to short-wave-
length (450 nm to 480 nm) light (Brainard et al. 2001,
Thapan et al. 2001, and Rea et al. 2005). Most electric
light sources illuminating our indoor environments
are designed to support the visual system by providing
relatively low levels of light dominated by wavelengths
near 555 nm, the peak of the photopic luminous effi-
ciency function (CIE 1978). Moreover, for conve-
nience, electric light sources are available night or day
and for variable durations. More and more then, people
throughout the world are living under a roof illumi-
nated by electric light sources, exposing them to dim
days and extended dim light at night, separating them
from the robust, natural light-dark cycle.
Studies have shown that adolescents report going to
bed later as they get older (Crowley et al. 2007). These
age-related changes in bedtimes have been associated
with reduced parental influence on bedtimes, increased
homework and extra-curricular activities, and other
activities such as playing on computers and watching
television. Evidence to date supports the hypothesis
that adolescents have a late circadian phase, contribut-
ing to these late bed times. With a highly structured
school schedule requiring early rising, these adoles-
cents typically experience reduced sleep durations.
Indeed, on unrestricted weekends, adolescents rise 1.5
to 3 hours later than they do on weekdays (Crowley et
al. 2007).
Light during the day is important for entrainment;
that is, for aligning circadian phase to the rest-activ-
ity cycle required by attending school. For reasons
described above, however, electric lighting, including
that common in schools, may not provide adequate
light for circadian entrainment. Without a robust light
stimulus during the day then, adolescents would logi-
cally be expected to exhibit late circadian phase and
therefore go to bed late and experience restricted sleep.
Daily morning short-wavelength light exposures
(after minimum core body temperature) are expected
to slightly advance the clock every day and thereby
maintain entrainment to the solar day (Jewett et al.
1997). The impact of reduced daily short-wavelength
light exposure on the circadian system of young adults,
as might be experienced by students without adequate
daylight (or electric light) exposure, has never been for-
mally investigated. A simple before-and-after, within-
subjects field experiment was conducted in a school
with documented good daylight design to determine
whether removal of short-wavelength light on five con-
secutive school days would delay circadian phase rela-
tive to a baseline measurement obtained prior to the
intervention.
METHODS
Site
The study was conducted at Smith Middle School,
Chapel Hill, North Carolina in May 2009. Smith Middle
School is unusual with respect to current architectural
practice in terms of the amount of daylight provided to
interior spaces (LRC 2004). The building uses south-
facing roof monitor skylights in most spaces to deliver
daylight to the interior spaces. Diffuse toplight ing pre-
vents occlusions due to blinds or wall displays typi cal
of sidelighting. To minimize glare from direct sunlight
entering the spaces, light entering the roof monitor is
baffled with cloth partitions; only diffuse light enters
the conditioned room. The electric lighting system is
controlled with motion sensors and photosensors that
modulate the fluores cent lamp output with dimming
ballasts. This strategy allows electric lights to be off
most of the day for electric energy savings.
The daylighting conditions were evaluated as part
of an extensive case study in 2004 (LRC 2004). On a
sunny afternoon in March 2004, researchers measured
light levels on several surfaces in a classroom with a
calibrated illuminance meter having a photopic spectral
response (CIE 1978). At the time of the site measure-
ments, all illu mination was provided by daylight. Hori-
zontal light level measurements were made by placing
the illuminance meter on desks; these ranged from
1330–2150 lux. Vertical illu minances on the chalkboard
ranged from 996–1 265 lux. The vertical light measure-
ments were made by placing the illuminance meter on
the chalkboard at eye level. Typical levels found in spaces
illuminated only by electric light sources are approxi-
mately 80% lower. That is, these illuminance levels
were approximately 5× higher than commonly found in
buildings only illuminated by electric lights. Based on
calculations using the model of human circadian pho-
totransduction developed by Rea and colleagues (2005),
these vertical illuminance levels would result in at least
60% melatonin suppression (at night), suggesting that
the light stimulus students receive in Smith’s classrooms
is strong enough to activate the circadian system. Based
upon results by Zeitzer et al. (2000) who showed that
the half maximum saturation for phase shifting was
80–160 lux from cool white fluorescent light sources for
a 6.5 hr exposure, the light levels measured in Smith
Middle School would also be highly effective for phase
shifting and, therefore, entrainment. Battery-powered
monitoring devices also recorded illumin ances on the
teacher’s desk over a long period of time. The desk was
located near the perimeter of the room rather than
directly under the roof monitor. These illuminance
levels aver aged 550 lux on sunny days and 320 lux on
partly cloudy days. Based upon the previous measure-
ments, it was expected that students at Smith Middle
School would be exposed to some of the highest illu-
minances typically found in an in door classroom envi-
ronment, making this an appropri ate site for the study.
94
Copyright © 2010 Neuroendocrinology Letters ISSN 0172–780X www.nel.edu
Mariana G. Figueiro and Mark S. Rea
Procedures
The within-subjects study began at the school on a
Friday morning. Eleven subjects (nine males and two
females, ages 13–14 years) were given an explanation
about the study and were asked to wear orange glasses
that attenuated all light of wavelengths shorter than
about 525 nm from reaching the eyes (Figure 1) during
the study period, Monday to Friday on the following
week, from the time they awoke until they returned
home after school (approximately 15:00); thus, subjects
were required to wear the orange glasses during school
and on the commute to school in the morning when
they are likely to be exposed to daylight. Participants
were then asked to refrain from consuming caffeinated
products for the remainder of the day because saliva
samples would be gathered from them in the evening.
Finally, subjects were instructed to return to the school
at 19:00 for saliva sample collection. The participants
stayed in the dimly illuminated school library during
sample collection. All electric lighting was kept off and
all blinds were pulled down to avoid daylighting in the
space. The room was lit with a dim red light (less than
5 lux at the cornea), dur ing which time the participants
were allowed to watch movies, play games, read or
study. Serial saliva samples (Salivette, Sarstedt, Newton,
NC, USA) were collected every 30 mi nutes (from 19:30
to 23:00) to determine DLMO. The subjects chewed on
a plain cotton cylinder until saturated. These samples
were then, in turn, centrifuged and refrigerated by
the researcher. To pre vent contamination of the saliva
samples, the subjects were not allowed to eat or drink
between sample times. The re frigerated samples were
later sent to Pharmascan, Os ceola, WI, for melatonin
assay. On the next Friday evening, participants returned
to school at 19:00 to repeat the saliva sample data col-
lection in the dimly illuminated library. The study was
approved by Rensselaer Polytechnic Institute’s Institu-
tional Review Board and meets the international ethical
standards of this journal (Portaluppi et al. 2008).
RESULTS
DLMO, in decimal hours, was calculated for each subject
using a threshold of 4.0 pg/ml. DLMO was determined
by using linear interpolation between the melatonin
values that fell above and below threshold. DLMO for
the eleven subjects on the Friday prior to wearing the
orange glasses averaged 21.15±0.61 and DLMO for the
same subjects averaged 21.66±0.81 after five consecu-
tive days of wearing the orange glasses. One subject had
not achieved the threshold value (4 pg/ml) at 23:00 on
the second Friday, suggesting that his DLMO occurred
later than 23:00, but as a conservative estimate, we
used 23:00 as his DLMO time. Using a two-tail paired
students’ t-test, this difference was significant with a
probability of 0.006 of a Type 1 error. Figure 2 shows
the cumulative frequencies of DLMO for the partici-
pants before and after the orange glasses intervention.
DISCUSSION
In one respect the results of this field study are trivial
because they simply confirm what has been shown
before (Warman et al. 2003) namely that removing
short-wavelength light exposure in the morning delays
circadian phase. In another respect, however, the
results of this study are quite important because they
Figure 1. The spectral irradiance distribution (SIR) of daylight varies
continuously throughout the day at every location on the earth.
Shown here is the relative SIR of one, standard phase of daylight
(left ordinate), defined by CIE as illuminant D65 (Wyszecki &
Stiles 1982) to represent natural daylight at 6500 K. Also shown
is the spectral transmittance of the orange glasses (amber/
orange, UV Process Supply), in percent (right ordinate) used in
the study. Irrespective of the actual and highly variable SIR in
daylight present in Smith Middle School during the experiment,
the orange glasses would have attenuated all short-wavelength
light from both the natural and the electric sources seen by the
students.
Figure 2. Cumulative frequencies of DLMO for the students before
and after the orange glasses intervention.
95
Neuroendocrinology Letters Vol. 31 No. 1 2010 • Article available online: http://node.nel.edu
Lack of short-wavelength light during the school day delays dim light melatonin onset
validate controlled laboratory findings with actual field
measurements. Specifically, these data are consistent
with the inference that removing short-wavelength light
during school days delays circadian phase in 8th-grade
students. After five consecutive school days of wearing
orange glasses, DLMO was delayed by about 30 min-
utes. Although it is known that individual SCN clocks
can have different periods, the phase delay of about 6
minutes per day observed here is consistent with the
typical free-running period in humans of 24.18±0.04 hrs
(Czeisler et al. 1999). Therefore, both the direction and
the magnitude of the predicted effects from laboratory
studies were obtained in this field study.
It has been estimated that bedtime occurs approxi-
mately two to three hours after DLMO (Burgess et al.
2003; Burgess & Fogg 2008). Since the present results
showed that removing short-wavelength light during
the school day will delay DLMO, sleep times are likely
to be delayed as well. Wake-up times are fixed for most
students, so those who do not receive short-wavelength
light during the day will probably have reduced sleep on
school nights. One study showed that students who had
poorer performance in school were those who obtained
about 25 minutes less sleep per night and went to bed
on average 40 minutes later on school nights than those
who were good performers (Wolfson and Carskadon
1998). By extension then, those who do not get enough
short-wavelength light during the school day would
exhibit reduced scholastic performance.
These findings, bridging controlled laboratory
results to a real school environment, should have
important, and practical, implications for school design
because it seems necessary to expose students to short-
wavelength light during the early part of the day to
maintain entrainment. Conscious delivery of short-
wavelength light in schools may be a simple, effective,
non-pharmacological treatment for students to help
them increase sleep duration and, perhaps, scholastic
performance. Daylight in a school like that provided in
Smith Middle School appears to be an ideal source to
accomplish this goal because it can deliver the proper
quantity and spectrum as well as the proper timing
and duration of light exposure. Electric lighting could
also serve this purpose, but current electric lighting is
manufactured, designed and specified to meet visual
requirements. Electric lighting could have an advantage
over daylight for the purpose of circadian entrainment,
because electric lighting can be precisely controlled, not
only during the day, but during the night when expo-
sure to light emulating daylight would be counterpro-
ductive for entrainment. Indeed, electric lighting can
provide a complete 24-hour light exposure pattern to
help ensure entrainment, but these deliberations repre-
sent an entirely new framework for architectural light-
ing design and practice (Figueiro 2008).
ACKNOWLEDGMENTS
The authors would like to acknowledge the U.S.
Green Building Council (USGBC) for sponsoring this
research. The Trans-NIH Genes, Environment and
Health Initiative Grant U01 DA023822 also provided
support this project. The authors would also like to
thank Dr. Mary Carskadon and Dr. Stephanie Crowley
of Brown University and Bradley Hospital for helping
with the DLMO calculations. A. Bierman, D. Guyon, J.
Brons, B. Plitnick, R. Leslie, and J. Taylor of the Lighting
Research Center, Rensselaer Polytechnic Institute, are
thanked for their assistance with this project and manu-
script. We would also like to thank the staff, teachers,
and principal of Smith Middle School for making this
project possible. And, finally, we would like to thank the
students and parents who participated in this research
project.
REFERENCES
1 Brainard G, Hanifin J, Greeson J, Byrne B, Glickman G, Gerner E, et
al. (2001). Action spectrum for melatonin regulation in humans:
Evidence for a novel circadian photoreceptor. J Neurosci. 21:
6405–6412.
2 Burgess HJ, Savic N, Sletten T, Roach G, Gilbert SS, Dawson D.
(2003). The relationship between the dim light melatonin onset
and sleep on a regular schedule in young healthy adults. Behav.
Sleep Med. 1: 102–114.
3 Burgess HJ, Fogg LF. (2008). Individual differences in the amount
and timing of salivary melatonin secretion. PLoS One. 3(8):
e3055.
4 Commission International de l’Eclairage (CIE). (1978). Light as
a true visual quantity: Principles of measurement. Commission
Internationale de l’Eclairage, Paris.
5 Crowley SJ, Acebo C, Carskadon MA. (2007). Sleep, circadian
rhythms, and delayed phase in adolescence. Sleep Med. 8:
602–612.
6 Czeisler C, Duffy JF, Shanahan TL, Brown EN, Mitchell JF, Rimmer
DW, et al. (1999). Stability, precision, and near-24-hour period of
the human circadian pacemaker. Science 284: 2177–2181.
7 Figueiro MG. (2008). A proposed 24 hour lighting scheme for
older adults. Light. Res. Technol. 40: 153–160.
8 Jewett M, Rimmer DW, Duffy JF, Klerman EB, Kronauer RE,
Czeisler CA. (1997). Human circadian pacemaker is sensitive to
light throughout subjective day without evidence of transients.
Am. J. Physiol. Regul. Integr. Comp. Physiol. 273: R1800–R1809.
9 Lewy AJ, Werh TA, Goodwin FK, Newsome DA, Markey SP. (1980).
Light suppresses melatonin secretion in humans. Science 210:
1267–1269.
10 Lighting Research Center. (2004). Daylight Dividends Case Study:
Smith Middle School, NC. Rensselaer Polytechnic Institute, Troy,
N.Y., 12 pp.
11 Portaluppi F, Touitou Y, Smolensky MH. (2008). Ethical and
methodological standards for laboratory and medical biological
rhythm research. Chronobiol. Int. 25: 999–1016.
12 Rea M, Figueiro MG, Bullough J. (2002). Circadian photobiology:
An emerging framework for lighting practice and research. Light.
Res. Technol. 34: 177–190.
13 Rea M, Figueiro MG, Bullough J, Bierman A. (2005). A model of
phototransduction by the human circadian system. Brain Res.
Rev. 50: 213–228.
96
Copyright © 2010 Neuroendocrinology Letters ISSN 0172–780X www.nel.edu
Mariana G. Figueiro and Mark S. Rea
14 Refinetti R. (2006). Circadian physiology. 2nd ed. CRC Taylor &
Francis, Boca Raton, London, New York.
15 Stevens R, Rea M. (2001). Light in the built environment: Poten-
tial role of circadian disruption in endocrine disruption and
breast cancer. Cancer Causes Control 12: 279–287.
16 Thapan K, Arendt J, Skene DJ. (2001). An action spectrum for
melatonin suppression: evidence for a novel non-rod, non-cone
photoreceptor system in humans. J. Physiol. 535(Pt 1): 261–267.
17 Warman VL, Dijk DJ, Warman GR, Arendt J, Skene DJ. (2003)
Phase advancing human circadian rhythms with short wave-
length light. Neurosci Lett. 342(1–2): 37–40.
18 Wolfson AR, Carskadon MA. (1998). Sleep schedules and daytime
functioning in adolescents. Child Dev. 69: 875–887.
19 Wyszecki G, Stiles W. (1982). Color science: Concepts and meth-
ods, quantitative data and formulae. 2nd ed. Reprinted in 2000.
John Wiley and Sons, New York.
20 Zeitzer J, Dijk D, Kronauer R, Brown E, Czeisler C. (2000). Sensitiv-
ity of the human circadian pacemaker to nocturnal light: Mela-
tonin phase resetting and suppression. J. Physiol. 526: 695–702.
... Providing for long-distance views allows students to rest their eyes to prevent eyestrain and visual acuity problems [103]. Experiencing a lack of natural daylight contributes to delayed sleep onset times in adolescents, resulting in difficulties with morning waking times [119]. Further, moisture and dampness, via mould and dust mites, has shown to increase the incidence of asthma and respiratory infections [100]. ...
Article
This review contributes to the debate regarding feedback needed by architects and building designers to improve the sustainability of their building designs. It utilizes the Integral Sustainable Design framework to harness a more comprehensive definition of sustainability to examine the breadth of currently possible feedback to building designers. The review acknowledges the multiple stakeholders that partake in different stages of a building project and focusses specifically on feedback from completed buildings for architects and designers. This review has endeavoured to summarize the range of current feedback which may be available to architects and draw conclusions regarding the usefulness of some of the assessment methods. There are some aspects of sustainability that have well developed and agreed feedback measures, such as energy use, embodied energy, and Indoor Air Quality. Other aspects about which there has been some research but no agreement on feedback include feeling safe, ecosystem services, and inclusiveness. This review reveals important feedback aspects not covered by either research, sustainability ratings schemes or post occupancy evaluation methods. Indeed, there are many aspects of the sustainability of school buildings about which very little is known, such as physical externalities and community services and the building's effect on socialisation and sense of place. Direct feedback in these areas will increase the pace of sustainability improvement in school design. However, further research is required to determine aspects about which architects desire feedback would find most useful and to develop efficient feedback methods. t.
... 10,112 When measured across a divergent series of real-world or in-lab conditions, sparser patterns of ambient illumination (with lower zeitgeber strength) during the day also associate with later sleep initiation, less sleep pressure/slow-wave-sleep buildup under states of rest or sleep deprivation, more nighttime awakenings, worse perceptions of sleep quality, less circadian-robust sleep cycles, and increases in reported insomnia symptoms. [113][114][115][116][117][118][119][120][121][122][123][124][125][126] These results are consistent with seasonally oriented studies of participants stationed in Antarctica that quantified (1) melatonin suppression, (2) increased pupillary constriction, and (3) delayed phasing of the sleep-wake cycle in winter versus summer. 127,128 Converging lines of evidence suggest that sensitivity to LAN increases when there is a lack of preceding daytime light, raising the possibility-in turn-that the health vulnerabilities associated with LAN can be counteracted or neutralized by adequate exposure to sunlight or electric indoor lighting. ...
Article
Full-text available
Fabian-Xosé Fernandez Department of Psychology, University of Arizona, Tucson, AZ, USACorrespondence: Fabian-Xosé FernandezDepartment of Psychology, University of Arizona, Tucson, Az, USAEmail FabianF@email.arizona.eduAbstract: This perspective considers the possibility that daytime’s intrusion into night made possible by electric lighting may not be as pernicious to sleep and circadian health as the encroachment of nighttime into day wrought by 20th century architectural practices that have left many people estranged from sunlight.Keywords: human-centric lighting, sleep, circadian entrainment, photohistory, sunlight, daylight
... Also, not receiving sufficient short-wavelength light during the morning was found to delay sleep onset and reduce sleep duration in adolescents, which in turn can result in poorer academic performance. 86,87 The spectral composition of daylight changes over the course of the day: in the morning there is a higher content of shorter wavelength blue light compared to the late afternoon, when the proportion of longer wavelength red light increases. 4 Based on this model, where indoor daylight provision is insufficient, blueenriched bright light at the correct times of day, particularly in the morning, could also be used to synchronise circadian rhythms, correct disrupted sleep or increase alertness. ...
Article
Typical home lighting practice is mainly centred on visual aspects to enable safe movement between spaces, flexibility in multiuse spaces, a sense of aesthetics and energy efficiency. Whilst lighting impacts on the health of residents have not received similar consideration, this area is gaining increasing interest. This is even more important and actual in the context of the recent pandemic where people have been working or studying from home. A combination of bright daytime light and night-time darkness is essential for circadian entrainment and maintenance of a regular daily sleep–wake cycle, whereas exposure to light at night can negatively impact circadian rhythms and sleep patterns and ultimately lead to potential health problems. Additionally, lighting also has the potential to affect health through associated effects such as flicker, glare, optical hazards or electromagnetic fields. This article discusses the main areas of concern related to home lighting and outlines general recommendations to limit detrimental effects and contribute to good health.
... This experiment was conducted in a room of (3.0×3.2) m 2 mimicking an office layout without windows to avoid effects of daylighting, as shown in Fig. 2. Six 11-channel LED tunable lighting devices were used as light sources. Circadian lighting conditions were designed according to the surveyed research results, which showed that the CS value greater than or equal to 0.3 could increase worker alertness [16] and improve the sleep quality [24,25]. Besides, to explore the isolated effects of CS, the biggest difference of CS values in the same CCT (6500 K) and illuminance (300 lx) were adopted with consideration of the typical lighting condition in an office environment. ...
Article
Non-image-forming lighting effects reveal the multiple circadian influences of light on human behaviours. A psychophysical experiment was conducted in two sessions (morning and afternoon) for 60 days. The experiment was designed to explore the influence of different circadian lighting by spectral tuning with controlled CCT and illuminance on attention level, brain activity, and sleep quality by measuring PVSAT, EEG, and PSQI, respectively, by 20 participants. The results showed that the white lighting of high circadian stimulus level and high melanopic irradiance significantly enhances the attention level, brain activity, and sleep quality compared to low circadian stimulus level.
... The time point of the DLMO is defined as the first of the three consecutive samplings. If the DLMO on the intervention day does not appear in the test period, it is suggested that the DLMO occurred after 23:00, as a conservative estimate, 23:00 will be set as the DLMO time [66]. The melatonin level was measured using the commercially available ELISA kit (Shanghai Keshun Biological Technology Co., Ltd.). ...
Article
Full-text available
Light has been found to affect the circadian clock of the human body. This study aims at exploring the proper light scheme for improving performance and alleviating the negative effects of phase-advance jet lag. Herein, the light intervention intensity during an 8-h working time after a simulated eastward flight is set as a variable. 27 healthy young adults participate in a 7-day circadian phase control and 4-day closed circadian conversion experiment. Participants are assigned to three groups according to lighting conditions: (1) control lighting group (CLG), (2) low-intervention group (LIG), and (3) high-intervention group (HIG). The alertness, sleep quality, and circadian phases of the participants are measured during the closed circadian conversion stage. Statistical analysis results show that, compared to CLG, HIG can effectively reduce the effect of the phase-advance jet lag syndrome on alertness during daytime (p = .028), improve short-term memory task performance (p < .001), and reduce visual fatigue (p = .016); besides, the 8-h light intervention during daytime assists in improving sleep quality. The results for dim light melatonin onset (DLMO) evidence that the HIG scheme can advance the circadian phase by 7.17 ± 0.71 h and is thus recommended for adjusting phase-advance jet lag in interior public workplaces. Finally, a model between light stimulus intensity and the circadian phase shift is deduced with a high correlation R² > 0.99.
... At a minimum, learning environments should be safe for students and staff and conducive to student motivation and engagement. Environmental quality elements such as fresh air and natural light are important for keeping students healthy and alert (Wyon and Wargocki 2007;Figueiro and Rea 2010). Additionally, a recent study from the United Kingdom (Box 2) found that measurable School infrastructure is a critical element of the learning environment and has an impact on student learning outcomes. ...
Technical Report
Full-text available
The purpose of this report on Uzbekistan Education Sector Analysis (ESA) is to provide a comprehensive overview of outcomes and challenges in the country’s education sector with a focus on access, quality, and relevance of education. The report focuses on providing a breadth of analysis, covering all levels of the education system, with in-depth analysis of certain challenges depending on data availability and quality. This ESA describes the current state of education outcomes and system performance as well as the reform environment across the sector. It assesses areas where the country has made progress as well as areas for further improvement. A key message is that the reform agenda in Uzbekistan is ambitious. While this agenda represents a considerable effort on the part of the Government of Uzbekistan to meet the needs of its citizens for education and skills development, it also comes with a series of implementation challenges that should not be underestimated. Key systems for monitoring, quality measurement, and quality assurance are essential to support the reform progress and ensure that reforms translate into tangible results.
... Light can serve as a zeitgeber for the human clock (Merrow and Roenneberg 2001), and can help regulate melatonin suppression and phase shifts (Boyce et al. 2003;Duffy and Czeisler 2009). The lack of short wavelength light in the morning was shown to delay dim light melatonin onset (Figueiro and Rea 2010). Daylight in buildings influences occupant's visual and thermal comfort as well as their psychophysiological state. ...
Article
Sunlight is a multisensory phenomenon that can enhance occupant's comfort, health, and connection to the outside environment through its dynamic luminous and thermal attributes. One gap in the existing literature on sunlight exposure is in addressing the visual interest of sunlight patterns and its potential effects on visual comfort. This study employed an experimental procedure where 33 office workers were subjected to three different window and sunlight patterns: fractal pattern, striped pattern, and clear at an office building over three days (one condition per day). Subjective ratings and physical environmental measurements were collected and analyzed to understand differences among the three conditions. Results showed no significant differences in visual comfort or visual interest of sunlight patterns among the three conditions. Desk layout influenced visual interest and view quality ratings. The fractal and striped patterns negatively influenced view quality compared to the clear condition. These results suggest that the shape of window and sunlight patterns might have limited to no impact on visual comfort and interest in offices when workers are preoccupied performing typical office work.
Article
Рreference for later bedtimes and rise times characterize evening chronotypes. Evening chronotypes suffer from early work start times thereby contradicting their circadian rhythms, as a result, a late wake-up time on free days reflect an attempt to compensate for a sleep debt accumulated on work days. This leads to a misalignment in sleep timing between weekdays and weekends, known as social jetlag (SJL), which is associated with increased health risk. Here we analyze the risks that evening preferences related with SJL bear and their potential impact on health, and also talk about possible correction measures, primarily of a behavioral nature, using literature data from PubMed and Embase database. Evening chronotype can compromise the maintenance of a healthy lifestyle. Evening chronotypes are more prone to bedtime screen use, which can suppress melatonin rise and extend wakefulness activities far into the night, thus dragging sleep and meal timing to later periods. Preference towards later time-of-day is linked with higher intake of total calories and fats, as well as unhealthy dietary habits (breakfast skipping, snacking, longer eating duration). Evening chronotype also has been associated with high caffeinated drinks intake, alcohol consumption and smoking, low physical activities. It has been found that unhealthy behavior might function as the promoting factors to circadian misalignment and greater SJL. Interventions to prevent and control unhealthy behaviors among evening types should be included in preventive measures of SJL.
Article
The issues of light non-visual influence on the human body during the work of office workers and students of educational institutions are considered. The necessity of creating a high-quality lighting environment of educational premises and offices by means of the corresponding dynamic lighting scenario taking into account non-visual effects of visible light is substantiated. The necessity of light levels revision of on working surfaces taking into account circadian effects is shown. The rapid development and increasing growth of LED lighting, which allows to obtain dynamic light scenes, as well as progress in knowledge of physiological mechanisms that regulate circadian rhythms, and their relationship with light stimuli allows to implement really high quality artificial lighting. The light environment not only affects the visual characteristics, but also has a significant impact on people through the so-called non-visual effects or those that do not form images (BOZ-effects) - mood, vivacity, circadian rhythms and more. It is important to combine visual and non-visual requirements with innovative lighting systems. Circadian lighting should always be evaluated at eye level, in the typical location of human existence in a specific internal environment. The improved lighting scenario involves synchronizing the light with the activity and circadian rhythms of consumers over a 24-hour cycle. Lighting in the auditoriums of educational institutions should meet the necessary visual requirements and create comfort for pupils and students. Audience lighting can be more efficient than lighting dynamics or dynamic lighting levels and color temperature. Automatic lighting control, which depends on the dynamics of daylight and should usually be built into the smart installation of dynamic lighting, should be a must.
Article
Full-text available
Internationally, it is said that the “era of sleeping difficulty” has arrived, and for Japanese children, this is no exception. On the other hand, it is well-established that daytime light reception promotes phase advances in melatonin secretion. Thus, it is undeniable that the sleep situation and melatonin secretion patterns of schoolchildren may depend on whether the classroom seat where they spend a relatively long time during a school day is on the window side of the classroom. This study examined the relationship between classroom seat location and children's sleep situation and melatonin secretion patterns. Our subjects were 88 elementary school children (47 boys and 41 girls) from the 5th to 6th grades enrolled in public elementary schools in Tokyo; we analyzed the data of 73 (37 boys and 36 girls) with whom there was no data loss. The study was carried out on weekdays from September to October 2018. From the analysis, a 1.7-times difference in the average illuminance median was observed between seats that were on the window side and those on the corridor side (window side group: 362.2 lx, control group: 207.7 lx) In addition, the odds ratio of children with high melatonin (night to morning) was 10-times higher in the window side group than in the control group (OR=10.179, 95% CI=1.492-69.455). Based on our findings, we conclude that the sleep situation of children should be an important determinant in classroom seating.
Article
Full-text available
The endogenous melatonin onset in dim light (DLMO) is a marker of circadian phase that can be used to appropriately time the administration of bright light or exogenous melatonin in order to elicit a desired phase shift. Determining an individual’s circadian phase can be costly and time-consuming.We examined the relationship between theDLMOand sleep times in 16 young healthy individuals who slept at their habitual times for a week. TheDLMOoccurred about 2 hours before bedtime and 14 hours after wake. Wake time and midpoint of sleep were significantly associated with the DLMO (r = 0.77, r = 0.68 respectively), but bedtime was not (r = 0.36). The possibility of predicting young healthy normally entrained people’s DLMOs from their sleep times is discussed.
Article
Full-text available
Alzheimer's disease (AD) patients exhibit random patterns of rest and activity rather than the consolidated sleep/wake cycle found in normal, older people. Light treatment has been shown to improve rest and activity rhythms and sleep efficiency of AD patients, presumably through consolidation of their circadian rhythms. The circadian system is maximally sensitive to short-wavelength radiation. Two independent studies summarised here show that 30 lux at the cornea of blue light (λ max = 470 nm) from light emitting diodes (LEDs) for 2 h in the early evening improved sleep efficiency of older adults, including those with AD compared to exposure to the same dose of red light. Because compliance to blue light treatment may be difficult for adults with AD, we conceived of a lighting scheme that might be more practical and as effective. White light dosages of different spectra and amounts for night and for day, based on a computational model for human circadian phototransduction, might be more readily accepted by seniors and by their caregivers. Implications for an improved visual environment and for better sleep efficiency of older adults are discussed.
Article
Full-text available
Regulation of circadian period in humans was thought to differ from that of other species, with the period of the activity rhythm reported to range from 13 to 65 hours (median 25.2 hours) and the period of the body temperature rhythm reported to average 25 hours in adulthood, and to shorten with age. However, those observations were based on studies of humans exposed to light levels sufficient to confound circadian period estimation. Precise estimation of the periods of the endogenous circadian rhythms of melatonin, core body temperature, and cortisol in healthy young and older individuals living in carefully controlled lighting conditions has now revealed that the intrinsic period of the human circadian pacemaker averages 24.18 hours in both age groups, with a tight distribution consistent with other species. These findings have important implications for understanding the pathophysiology of disrupted sleep in older people.
Article
Full-text available
A century of research and practice have optimized the use of electric lighting in buildings to support human vision. However, recent lines of research show that light is also important to human circadian regulation, as reflected in such diverse phenomena as depression, sleep quality, alertness, and, perhaps, even health. Although light is essential to both vision and circadian regulation, research shows that the biophysical processes that govern circadian regulation are very different from those that govern vision. This growing body of research will probably influence the architectural lighting community and manufacturers to reoptimize the use of electric lighting in buildings to support both human vision and circadian functions. The present paper is concerned with establishing a framework for lighting practice and applied research that will assist lighting practitioners and manufacturers in interpreting this emerging research.
Article
Full-text available
The absolute and spectral sensitivities to light by the human circadian system, measured through melatonin suppression or phase shifting response, are beginning to emerge after a quarter century of active research. The present paper outlines a hypothesized model of human circadian phototransduction that is consistent with the known neuroanatomy and physiology of the human visual and circadian systems. Spectral opponency is fundamental to the model, providing a parsimonious explanation of some recently published data. The proposed model offers a framework for hypothesis testing and subsequent discussion of the practical aspects of architectural lighting with respect to light and health.
Article
Full-text available
The main objectives of this article are to update the ethical standards for the conduct of human and animal biological rhythm research and recommend essential elements for quality chronobiological research information, which should be especially useful for new investigators of the rhythms of life. A secondary objective is to provide for those with an interest in the results of chronobiology investigations, but who might be unfamiliar with the field, an introduction to the basic methods and standards of biological rhythm research and time series data analysis. The journal and its editors endorse compliance of all investigators to the principles of the Declaration of Helsinki of the World Medical Association, which relate to the conduct of ethical research on human beings, and the Guide for the Care and Use of Laboratory Animals of the Institute for Laboratory Animal Research of the National Research Council, which relate to the conduct of ethical research on laboratory and other animals. The editors and the readers of the journal expect the authors of submitted manuscripts to have adhered to the ethical standards dictated by local, national, and international laws and regulations in the conduct of investigations and to be unbiased and accurate in reporting never-before-published research findings. Authors of scientific papers are required to disclose all potential conflicts of interest, particularly when the research is funded in part or in full by the medical and pharmaceutical industry, when the authors are stock-holders of the company that manufactures or markets the products under study, or when the authors are a recent or current paid consultant to the involved company. It is the responsibility of the authors of submitted manuscripts to clearly present sufficient detail about the synchronizer schedule of the studied subjects (i.e., the sleep-wake schedule, ambient light-dark cycle, intensity and spectrum of ambient light exposure, seasons when the research was conducted, shift schedule in studies involving shift work, and menstrual cycle stage in studies involving young women). Rhythm analysis of time series data should be performed with the perspective that rhythms of different periods might be superimposed upon the observed temporal pattern of interest. A variety of different and complementary statistical procedures can be used for rhythm detection. Fitting a mathematical model to the time series data provides a better and more objective analysis of time series data than simple data inspection and narrative description, and if rhythmicity is documented by objective methods, its characterization is required by relevant parameters such as the rhythm's period (tau), MESOR (time series average), amplitude (range of temporal variation), acrophase (time of peak value), and bathyphase (time of trough value). However, the assumptions underlying the time series modeling must be satisfied and applicable in each case, especially the assumption of sinusoidality in the case of cosinor analysis, before it can be accepted as appropriate. An important aspect of the peer review of manuscripts submitted to Chronobiology International entails judgment of the conformity of research protocols and methods to the standards described in this article.
Article
Full-text available
Background The aim of this study was to examine individual differences in a large sample of complete melatonin profiles not suppressed by light and search for possible associations between the amount and timing of melatonin secretion and a multitude of lifestyle variables. The melatonin profiles were derived from saliva samples collected every 30 minutes in dim light from 85 healthy women and 85 healthy men aged 18–45 years. There was a large individual variability in the amount of melatonin secreted with peak values ranging from 2 to 84 pg/ml. The onset of melatonin secretion ranged from 18:13 to 00:26 hours. The use of hormonal birth control, reduced levels of employment, a smaller number of days on a fixed sleep schedule, increased day length and lower weight were associated with an increased amplitude of melatonin secretion. The use of hormonal birth control, contact lenses, a younger age, and lower ratings of mania and paranoia were associated with a longer duration of melatonin secretion. An earlier occurrence of the onset of melatonin secretion was associated with an earlier wake time, more morningness and the absence of a bed partner. Lifestyle and behavioral variables were only able to explain about 15% of the individual variability in the amount of melatonin secretion, which is likely because of a substantial genetic influence on the levels of melatonin secretion.
Article
This paperback reprint of a classic book deals with all phases of light, color, and color vision, providing comprehensive data, formulas, concepts, and procedures needed in basic and applied research in color vision, colorimetry, and photometry.
Article
Life in industrialized societies is primarily life inside buildings. Illumination from electric lighting in the built environment is quite different from solar radiation in intensity, spectral content, and timing during the 24-hour daily period. Humans evolved over millions of years with the day–night pattern of solar radiation as the primary circadian cue. This pattern maintained a 24-hour rhythm of melatonin release, as well as a host of other physiological rhythms including the sleep–wake cycle. Electric lighting in the built environment is generally more than sufficient for visual performance, but may be inappropriate for the maintenance of normal neuroendocrine rhythms in humans; e.g., insufficient during the day and too much at night. Lighting standards and engineering stress visual performance, whereas circadian function is not currently emphasized. The molecular biological research on the circadian clock and on mechanisms of phototransduction makes it clear that light for vision and light for circadian function are not identical systems. In particular, if electric lighting as currently employed contributes to `circadian disruption' it may be an important cause of `endocrine disruption' and thereby contribute to a high risk of breast cancer in industrialized societies.