Content uploaded by Watchara Sroykham
Author content
All content in this area was uploaded by Watchara Sroykham on Apr 22, 2014
Content may be subject to copyright.
Abstract— Melatonin is a circadian hormone transmitted via
suprachiasmatic nucleus (SCN) in the hypothalamus and
sympathetic nervous system to the pineal gland. It is a hormone
necessary to many human functions such as immune,
cardiovascular, neuron and sleep/awake functions. Since
melatonin enhancement or suppression is reported to be closely
related to the photic information from retina, in this paper, we
aim further to study both the lighting condition and the
emotional self-regulation in different lighting conditions
together with their effects on the production of human
melatonin. In this experiment, five participants are in three
light exposure conditions by LED backlit computer screen (No
light, Red light (~650nm) and Blue light (~470nm)) for 30
minute (8-8:30pm), then they are collected saliva both before
and after the experiments. After the experiment, the
participants are also asked to answer the emotional self-
regulation questionnaire of PANAS and BRUMS regarding
each light exposure condition. These results show that positive
mood mean difference of PANAS between no light and red light
is significant with p=0.001. Tension, depression, fatigue,
confusion and vigor from BRUMS are not significantly
changed while we can observe the significant change in anger
mood. Finally, we can also report that the blue light of LED-
backlit computer screen significantly suppress melatonin
production (91%) more than red light (78%) and no light
(44%).
I. INTRODUCTION
Melatonin or N-Acetyl-5-methoxytryptamine is a circa-
dian hormone. It is rhythmically produced by the pineal
grand in the brain with a low level during daytime and a high
level during nighttime. The level of melatonin rises during
the evening (8-11pm). It will reach the peak level between 2-
4am and decrease to the baseline level during late morning
(8-10am). This mechanism is controlled by the suprachias-
matic nucleus (SCN) which is inhibited by light and is
stimulated by darkness. Melatonin is also known as a
hormone necessary to many human functions such as
immune, cardiovascular, neuron and sleep/awake functions.
In recent, technology development has led to energy-
saving and effective electronic devices. The Light-Emitting
Diode (LED) is one of those. It is widely used in display of
This project is supported in part by the government funding of Mahidol
University.
W. Sroykham is with the Department of Biomedical Engineering,
Mahidol University, 25/25 Putttamonthon 4, Salaya, Nakornpathom 73170
Thailand and with Center for Biomedical Instrument Research and
Development, Institute of Molecular Biosciences,Mahidol University, 25/25
Putttamonthon 4, Salaya, Nakornpathom 73170 Thailand(e-mail:
watchara.sro@mahidol.ac.th).
Y. Wongsawat is with the Department of Biomedical Engineering,
Mahidol University, 25/25 Putttamonthon 4, Salaya, Nakornpathom 73170
Thailand (corresponding author, phone: 66-82-889-2138 Ext 6361; fax: 66-
82-889-2138 Ext 6366; e-mail: yodchanan.won@mahidol.ac.th).
electronic device such as smart mobile phone, television,
desktop computer, notebook computer and tablet. However,
the light form this device can suppress human melatonin
production. Recently Studies, Wood et al (2013) showed that
melatonin production can be suppressed after 1-2 hours by
tablet with blue LEDs [1]. Cajochen et al (2011) showed that
LED-backlit computer screen can significantly suppressed
human melatonin production more than a non-LED backlit
computer screen [2]. Furthermore, Figueiro et al (2011)
showed that light from cathode ray tube computer screen can
slightly suppressed human melatonin production and has
suggested that the light from electrical devices at nighttime
can suppress human melatonin production [3]. Lewy et al
also showed that melatonin secretion in human can be
suppressed by artificial light [4].
Besides the lighting condition, in parallel studies, stress,
alertness and mood generated by both human themselves and
environment are reported to have the effects on melatonin
production. Plitnick et al (2010) showed that red light and
blue light at nighttime can increase the beta-wave of
electroencephalogram (12-30 Hz) and stimulate alertness and
momentary mood and reduce sleepiness [5]. Cajochen et al
(2005) showed that light at 460 nm stimulate alertness, effect
on thermoregulation and heart rate, suppress melatonin
production more than light at 550 nm [6]. Even though the
research on lighting condition and emotion have been widely
done, however, the correlation and connection between light
and emotional self-regulation that have effect on melatonin
production still missing. Therefore, in this paper, we
emphasize on the effect of light from LED and emotional
self-regulation in different light conditions on human
melatonin production through the use of saliva-based
hormone detection, enzyme-linked immunosorbent assay
(ELISA) technique.
II. MATERIALS AND METHODS
A. Participants
Five healthy participants with normal color vision (three
male and two female) were recruited. The mean age of the
participants was 25.4 years (SD = 2.24) with a range of 23-29
years old. All Participants did not take a prescription
medication, alcohol and smoking before and during the study.
B. Study protocol
All participants arrived at the laboratory at 7:45pm and
washed their mount for 5 minutes before collecting the saliva
in the collecting tube. At 8pm, all participants started testing
each light exposure conditions in the testing room with
controlled room temperature at 250C. All participants sited
on the chair which was 1-meter far from the LED-backlit
Effects of LED-backlit Computer Screen and Emotional Self-
regulation on Human Melatonin Production
Watchara Sroykham, Student Member, IEEE and Yodchanan Wongsawat, Member, IEEE
35th Annual International Conference of the IEEE EMBS
Osaka, Japan, 3 - 7 July, 2013
978-1-4577-0216-7/13/$26.00 ©2013 IEEE 1704
computer screen. This screen was used to generate different
light exposure conditions. All participants were in each light
exposure conditions for 30 minute and collected saliva in the
collecting tube at 8:30pm (One light exposure condition per
day). After that all participants were asked to answer the
emotional self-regulation questionnaire of Positive and
Negative Affect Scale (PANAS: Watson et al., 1998) [7] and
Brunel Mood Scale (BRUMS: Terry et al., 1999, 2003) [8-9]
for each light exposure condition. The study protocol is
summarized in Figure 1.
Figure 1. The study protocol: Participants were in no light, red light and
blue light in test room for 30 minute (8-8:30pm) each day for each ligting
condition. Saliva was collected before and after light exposure condition.
The PANAS and BRUMS were tested after finished testing.
C. Light exposure conditions
In this paper, three light exposure conditions, i.e. no light,
red light, and blue light, are employed. LED-backlit
computer screen is used to generate different light exposure
conditions. The screen is 20.0 inch with 0.2766 mm×0.2766
mm pixel pitch, resolution of 1600×900, and brightness of
250 cd/m2.
For the first condition (no light condition), LED-backlit
computer screen is turned off. For the second condition (red
light condition), LED-backlit computer screen is set to the
highest brightness with color temperature at the highest red
color levels together with the lowest green and blue color
level. This condition generates the long wavelength
(~650nm) light. Finally, for the third condition (blue light
condition), LED-backlit computer screen is set to the highest
brightness, color temperature at the highest blue color level
together with the lowest green and red color levels. This
condition generates the short wavelength (~470nm) light.
D. Emotional Self-regulation
Positive and Negative Affect Scale (PANAS) and Brunel
Mood Scale (BRUMS) are used to rate the scale of all
participants after the experiments. PANAS is a 20-item mood
scale and was developed to provide brief measurements of
positive and negative effects. Each item is scored on 1-5 (1
means ‘not at all’, 2 means ‘a little’, 3 means ‘moderately’, 4
means ‘quite a bit’ and 5 means ‘very much’).
BRUMS is a 24-item mood scale that measures 6
identifiable affective states (tension, depression, anger, vigor,
fatigue, and confusion). Each item is scored on 0-4 (0 means
‘not at all’, 1 means ‘a little’, 2 means ‘moderately’, 3 means
‘quite a bit’ and 4 means ‘extremely’).
E. Measurement of human saliva melatonin
Saliva was collected from five participants before testing
(8pm) and after finishing the experiment (8:30pm) for each
condition with clean collecting tubes and stored at ≤ -200C
refrigerator immediately. After that, before the analysis, all
collecting tubes were thawed at room temperature until being
back to liquid. Then, enzyme-linked immune sorbent assay
(ELISA) was used for direct human saliva melatonin
concentration measurement (Buhlmann Laboratories,
Schonenbuch, Switzerland) with sensitivity of 0.5 pg/ml and
linearity of 92.2 %. It is a competitive immunoassay using a
capture antibody technique. The Kennaway G280 anti-
melatonin antibody was coated onto the microtiter plate.
In the first step, microtiter plate is incubated for 3 hours.
The melatonin presented in the pretreated controls and
standards, respectively, compete with biotinylated melatonin
for the binding sites of this highly specific antibody. After
washing, streptavidin conjugated to the horseradish
peroxidase (enzyme label) is added. In the second step,
microtiter plate is incubated for 60 minutes. The melatonin-
biotin-antibody complexes are captured on the coated wells.
Unbound enzyme label is removed by the second washing
step and the TMB substrate is added to the wells. In the third
step, microtiter plate is incubated for 30 minutes. Colored
product is formed in the inverse proportion to the amount of
melatonin presented in the sample. The color turns from blue
to yellow after the addition of an acidic stop solution and can
be measured at 450 nm. Anthos Lucy2 microplatelumino-
meter is used to read the absorbance at 450 nm (Anthos
Labtec Instruments Ges.m.b.H., Wals/Salzburg, Austria).
Figure 2 presents human saliva melatonin ELISA kit.
Figure 2. Human saliva melatonin ELISA kit (Buhlmann Laboratories,
Schonenbuch, Switzerland).
III. RESULTS
A. Emotional Self-regulation
The positive effect value of PASNAS in no light, red light
and blue light conditions are 10.4, 14.8 and 13.0,
respectively. The negative effect value of PANAS in no light,
red light and blue light conditions are 13.2, 16.2 and 12.2,
respectively. Analysis of variance (ANOVA) reveals that the
mean difference of positive effect is significant at the 0.05
Saliva Collection Saliva Collection
20.00 pm 20.30 pm
No Light Red Light Blue Light
PANAS
BRUMS
1705
level (F=9.175, p =0.004) but the mean difference of negative
effect is not significant at the 0.05 level (F=1.752, p =0.215).
Multiple comparisons test of LSD (Least Significant
Difference) reveals that the mean difference is significant at
the 0.05 level of no light - red light (p=0.001) and no light -
blue light (p=0.027). The results are presented in Table 1 and
graphical results of PANAS in light exposure conditions are
presented in Figure 3.
The tension, anger, depression, fatigue, confusion and
vigor mood of BRUMS in no light of participants are 1.2,
0.4, 1.4, 3.2, 1.2 and 0.6, respectively. The tension, anger,
depression, fatigue, confusion and vigor mood of BRUMS in
red light of participants are 2.4, 3.4, 2.8, 2.2, 2.8 and 2.8,
respectively. The tension, anger, depression, fatigue,
confusion and vigor mood of BRUMS in blue light of
participants are 0.8, 1.0, 1.2, 2.2, 1.6 and 2.2, respectively.
Analysis of variance (ANOVA) reveals that the mean
difference of anger at the 0.05 level (F=10.500, p =0.002) is
significant, however, the mean differences of tension,
depression, fatigue, confusion and vigor are not significant at
the 0.05 level (F=1.195, p =0.336; F=1.239, p=0.324;
F=0.758, p=0.490; F=1.268, p=0.316 and F=1.416, p=0.280,
respectively). Moreover, the multiple comparisons test of
LSD (Least Significant Difference) reveals that the mean
difference of anger is significant at the 0.05 level of no light -
red light (p=0.001) and red light - blue light (p=0.005). The
results are presented in Table 1 and the graphical results of
BRUMS in light exposure conditions are presented in
Figure 4.
TABLE I. PANAS, BRUMS AND MELATININ SUPPRESION
Measure
Light exposure conditions
P-value
No light
Red light
Blue light
PANAS
Positive affect
10.4±0.6
14.8±2.6+
13.0±1.0+
0.004*
Negative affect
13.2±5.0
16.2±3.2
12.2±1.5
0.215
BRUMS
Tension
1.2±1.6
2.4±2.1
0.8±1.3
0.336
Anger
0.4±0.5
3.4±1.5+
1.0±1.0++
0.002*
Depression
1.4±2.1
2.8±1.9
1.2±1.1
0.324
Fatigue
3.2±1.6
2.2±1.1
2.2±1.6
0.490
Confusion
1.2±1.8
2.8±1.5
1.6±1.7
0.316
Vigor
0.6±1.3
2.8±2.6
2.2±2.3
0.280
Melatonin
suppression (%)
44±21
78±14+
91±12+
0.001*
Note: Values represent mean±SD. + = The mean difference is significant at the 0.05 level between
no light and red light, no light and blue light. ++ = The mean difference is significant at the 0.05 level
between red light and blue light. * = The mean difference is significant at the 0.05 level.
B. Human saliva melatonin
The percent of human saliva melatonin suppression in no
light, red light and blue light are 44%, 78% and 91%,
respectively. Analysis of variance (ANOVA) reveals that the
mean difference of melatonin suppression is at the 0.05 level
(F=11.778, p =0.001). Multiple comparisons test of LSD
(Least Significant Difference) reveals that the mean
difference is significant at the 0.05 level of no light - red light
(p=0.018) and no light - blue light (p=0.002). The results are
presented in Table 1 and the graphical results of melatonin
suppression (%) in light exposure conditions are presented in
Figure 5.
Figure 3. PANAS in light exposure conditions
Figure 4. BRUMS in light exposure conditions
0
5
10
15
20
No light Red light Blue light
Sum
Positive affect
Negative affect
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Mean
No light
Red light
Blue light
1706
Figure 5. Melatonin suppression (%) in light exposure conditions
IV. CONCLUSION
The aim of this study was to investigate the effects of
light from LED and emotional self-regulation in different
light conditions on healthy human melatonin production.
These results show that blue light of LED-backlit computer
screen significantly suppress melatonin production more than
red light of LED-backlit computer screen and no light. Many
studies have shown that blue light significantly inhibit
melatonin production at night since the blue light (460 nm)
has short wavelength with peak of sensitivity of melanopsin
[2-5]. However, it is also important to consider the long term
exposure and different intensities of brightness since these
factors also have the effects on human melatonin production.
In general, alertness, stress and mood can be reliably
measured by simply asking the participants or rating scale.
PANAS revealed that the positive effect of mood is
stimulated by red and blue light of LED backlit computer
screen more than no light, but the negative effect of mood is
not difference in each light exposure conditions. BRUMS
revealed that red light of LED- backlit computer screen can
stimulate tension, anger, depression and confusion moods
more than blue light and no light which are related to the
negative effect of mood. Vigor mood in red light condition is
also higher than blue and no light condition.
Red and blue light have effect on emotional self-
regulation more than no light because it stimulates stress,
alertness and momentary mood. This is related to the
melatonin production. Many studies have shown that red
light and blue light at nighttime increased beta-wave of
electroencephalogram (15-30 Hz), stimulated alertness and
momentary mood as well as reduce sleepiness [5-6].
Moreover, it also has direct and indirect effects via
suprachiasmatic nucleus (SCN) to brain areas implicated in
the regulation of arousal [10-11].
Intuitively speaking, the earth rotates around the sun
every day. This phenomenon causes day and night, or light
and darkness. The human have adapted to this phenomenon.
Human sleeps at night. This period is no light. It does not
suppress the melatonin production then human falling asleep.
In the morning, human wakes up by the light. This period
contains red light more than any light. It stimulates alertness
and suppresses melatonin production. During a day, this
period contains blue light more than any light. It suppresses
melatonin production. In the dusk, this period contains red
light more than any light again. It induces the melatonin
production more than blue light then human falling asleep.
In conclusion, blue light has effect on melatonin
production more than red light. Red light stimulates positive
affect and anger more than blue light. It also has effect on
melatonin production. Finally, this conclusion can be used to
design and develop the electrical display devices used before
sleep that cannot stimulate alerting or stress and suppress
melatonin production. Melatonin suppression by light at night
increases the risk for more serious diseases such as breast
cancer [12]. In addition, artificial light technology is used in
the design of more effective lighting at novel house or
workplace with no effect on human physiology and health
maintenance.
ACKNOWLEDGMENT
The project is supported in part by the government funding of
Mahidol University. We would like to thank Prof. Ahnond
Bunyaratavej and Dr. Monnipha Sila-Asna for discussion in results,
members of Cell Engineering and Tissue Growth Research Group
(CETG), members of Brain-Computer Interface Laboratory (BCI
Lab) of Mahidol University and all participants.
REFERENCES
[1] Wood B., Rea MS.,Plitnick B., and Figueiro M.G., “Light level and
duration of exposure determine the impact of self-luminous tablets on
melatonin suppression” Applied Ergonomics 44 (2013) 237-240,
2013.
[2] Cajochen C., Frey S., Anders D., Späti J., Bues M., Pross A., Mager
R., Wirz-Justice A., and Stefani O., “Evening exposure to a light-
emitting diodes (LED)-backlit computer screen affects circadian
physiology and cognitive performance” Journal of Applied
Physiology 110, 1432-1438, 2011.
[3] Figueiro MG., Plitnick B., Wood B., and Rea MS.,“The impact of
light from computer monitors on melatonin levels in college
students”Neuro Endocrinology Letters 32, 158-163, 2011.
[4] Lewy A.J., Thomas A., Frederick KG., David. AN., and Markey P.,
“Light suppression melatonin secretion in humans” Science,
210(4475), 1267-1269, 1980.
[5] Plitnick B., Figueiro M.G., Wood B., and Rea MS.,“The effects of red
and blue light on alertness and mood at night” Lighting Res. Technol,
1–10, 2010.
[6] Christian C., Mirjam M., Szymon K., Kurt K., Roland S., Peter O.,
Selim O., and Anna WJ.,“High Sensitivity of Human Melatonin,
Alertness, Thermoregulation, and Heart Rate to Short” The Journal of
Clinical Endocrinology & Metabolism 90(3):1311–1316, 2005.
[7] Watson D., Clark LA., and Tellegen A.,“Development and validation
of brief measures of positive and negative affect: The PANAS scales”
J Personal Social Psychol 54(6):1063–70,1998.
[8] Terry P.C., Lane A.M., Lane H.J. and Keohane L.,“Development and
validation of a mood measure for adolescents” Journal of Sports
Sciences 17, 861-872, 1999.
[9] Terry P.C., Lane AM. and Fogarty GJ., “Construct validity of the
Profile of Mood States - Adolescents for use with adults” Psychology
of Sport and Exercise 4, 125-139, 2003.
[10] Figueiro MG., Bierman A., Plitnick B., Rea MS. “Preliminary
evidence that both blue and red light can induce alertness at night”.
BMC Neuroscience 10: 105,2009.
[11] Gooley JJ., Lu J., Fischer D., and Saper CB., “A broad role for
melanopsin in nonvisual photoreception”. J Neurosci 23, 7093–106,
2003.
[12] Blask D., Sauer L., Dauchy R., Holowachuk E., and Ruhoff M., “New
insights into melatonin regulation of cancer growth” Advances in
Experimental Medicine and Biology, 460, 337-343, 1999.
44
78
91
0
10
20
30
40
50
60
70
80
90
100
No Light Red Light Blue Light
Melatonin Suppression (%)
1707