RUNNING HEAD: UNDERSTANDING THE EFFECTS OF LIGHT REGARDING MELATONIN
Understanding the Effects of Light Regarding Melatonin
Daniela I. Lin
Everglades High School
RUNNING HEAD: UNDERSTANDING THE EFFECTS OF LIGHT REGARDING MELATONIN 2
Table of Contents
Title Page (pg 1)
Table of Contents (pg 2)
Abstract (pg 3)
Introduction (pg 4-5)
Method (includes participants, materials, apparatus, and procedure) (pg6-7)
Results (pg 7)
Discussion (pg 8)
References (pg 9-11)
Tables/Figures (pg 12-15)
RUNNING HEAD: UNDERSTANDING THE EFFECTS OF LIGHT REGARDING MELATONIN 3
Melatonin is a sleep-inducing hormone that’s produced by the brain’s pineal gland it’s normally
suppressed only by daylight. Nowadays though, artificial daylight in our modern technology has been
found to mimic natural light confusing the brain into decreasing melatonin even at night too! Studies
conducted have shown that before (Fonken, L., & Nelson, R., 2011) artificial light present in devices had
been emitting mostly red wavelengths but now it has replaced with “bluish bulbs” to increase energy
efficiency. Through studies (utilizing precise dime-semeters and specialized googles) conducted by
Figueiro, M., Plitnick, B., Rea, M., & Wood, B. (2012), we can see that after 2 hours there is a significant
repression of melatonin.
Keywords: Melatonin, Blue Light, self-luminous devices, Circadian Rhythm, Artificial light
RUNNING HEAD: UNDERSTANDING THE EFFECTS OF LIGHT REGARDING MELATONIN 4
For more than 120 years, artificial light has been emitting mostly red wavelengths (for example
incandescent light bulbs). The problem now states Fonken, L., & Nelson, R. (2011) is that the artificial
light sources we use today are increasingly “becoming blue” or utilizing short blue wavelengths. He
estimates that 1.6 billion new computers, phones, and cellphones were sold last year alone. These
newer technologies were replaced with even “bluer bulbs” for increase energy efficiency.
In 1958, Woodland Hastings and Beatrice Sweeney (2010, January 1) tested the ability of
different wavelengths. They found that “the greatest power to reset the organism’s daily meter lay in
the blues.” Now studies show that light acts on the body on two pathways (the primary optic tract and
the retinohypothalamic tract). The primary optic tract is known to control over visual effects and visual
reflexes. While the retinohypothalamic tract controls the circadian, endocrine, and neurobehavioral
functions. Thus making the retinohypothalamic tract more sensitive to blue light exposure(energy
wavelength of about 459-485 nm). Blue’s power to “reset” circadian rhythms is not because of the color
but because of the fact that it more easily penetrates into the surface of oceans and photoreceptors
than other visible wavelengths(such as red=incandescent bulbs). Scientists believe that the color balance
of the sky might have helped preserve blue light’s reset role throughout history.
Electronic devices with overly brightened blue emitting displays can cause great suppression of
the hormone melatonin. Melatonin is a sleep-inducing hormone that is produced by the brain’s pineal
gland. Normally, daylight activates light sensitive retinal proteins that control our biological clock by
triggering signals to the brain’s suprachiasmatic nucleus (SCN). As a result, the SCN causes the pineal
gland to decrease its production of melatonin. However, as a result of artificial light in self-luminous
tablets mimicking the daylight the brain gets “confused” and decreases melatonin production during the
RUNNING HEAD: UNDERSTANDING THE EFFECTS OF LIGHT REGARDING MELATONIN 5
night too (instead of increasing it). Which explains why people nowadays are going to sleep later
Suppression of melatonin at night (by light) results in circadian disruption (our human biological
clock) which can lead to higher chances of obtaining diabetes, obesity, breast cancer, and other diseases.
To produce white lights electronic devices must emit at short wavelengths which is especially disrupts
our circadian rhythm. The 2011 “Sleep in America” poll released by the National Sleep Foundation (NSF)
has found that 43% of Americans between the ages of 13-64 said that they rarely/never get a good
night’s sleep during school weeks. More than half state that they have experienced some sort of sleep
problem often/every night (like snoring, waking at night, and feeling unrefreshed in the morning).
Overall, 95% of Americans surveyed admitted to using devices that emitted short wavelengths before
bedtime. These following results show potential positive correlation of artificial light and melatonin
suppression (which leads to inability to sleep). According to Michael Gradisar, PhD, Flinders University
(2011, March 7), baby boomers (46-64 years old), generation X'ers (30-45 year olds), generation Y'ers
(19-29 year olds), and generation Z'ers (13-18 year olds) all report very different technological
preferences (hence very different sleep patterns/schedules). Roughly 55% of generation Z'ers and 47%
of generation Y'ers say that they surf the Internet every night/ almost every night within the hour before
their bedtime. About 18% of generation Z'ers and 20% of generation Y’ers state that they are awakened
by a text message, phone call, or email after having gone to sleep(they state that this happens a few
times a week). As a result, generation Z’ers and generation Y’ers report more of an average sleepiness
than the baby boomers and generation X’ers. Meaning that suppression of melatonin affects teenagers
the most and thus it’s of utmost importance to restrict usage of modern technology.
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The materials utilized were a dime-simeter which is a small and inexpensive “data logging device”
that can record light and activity levels over many days. It can be worn as a badge, collar, hat, near the
eye, or etc. the size is comparable to a dime (hence the name). Also special glasses that absorbed or
blocked artificial Light, compact fluorescent light bulbs with differing color frequencies, and self-luminous
devices (more specifically an IPAD Air) accompanied it.
To ensure valid test results the participants chosen were around average age of the 18.9.
Individuals that possessed major health problems such as heart disease, diabetes, and high blood
pressure or were taking over the counter medication were excluded from the experiment. “Atypical
people” that were predisposed to rising earlier or later were also filtered out of the experiment through
a questionnaire. All of this made sure that melatonin production was made at the relatively same time in
all subjects (they approximated from 11:00 pm-1:00 am).
In order to test their theories, they gathered 13 individuals who utilized self-luminous tablets to
perform daily tasks (read, play games, watch movies, and etc.) The 13 participants were divided into
three groups (control group, extra melatonin suppression group, and no melatonin suppression group).
The first group was given a pair of clear goggles with blue light (470—nm). This was the group with
“extra melatonin suppression” because blue light is known to be a strong melatonin suppressor. The
second group used orange tinted glasses that filtered out short-wavelengths of radiation emitted by the
tablets (the “no melatonin suppression group”). The third and final group was the control group who
wore nothing and used the tablets like any other regular person. All three groups had their tablet set at
the brightest possible setting. A dime-simeter was worn close to the corners of the eye by each subject
to accurately record each person’s light exposure results. The research team hypothesized that the
amount of time exposed and the distance between the screen and the eye impacted how much
RUNNING HEAD: UNDERSTANDING THE EFFECTS OF LIGHT REGARDING MELATONIN 7
melatonin was inhibited. After a one hour exposure, the controlled group’s melatonin was repressed by
about 7%, the group with the blue goggles was about 48%, and the group with the tinted orange goggles
was not applicable (because it was used as a dark control in other words if measured it would be none
b/c their goggles were made to filter out all the light). Although melatonin levels were still rising they
rose lower than a normal person’s would if surrounded by pitch darkness. A two hour exposure showed
a significant amount of blockage (of the production of melatonin). The controlled group’s melatonin
was repressed by 23%, the blue goggles group was about 66%, and the orange tinted glasses group was
still not applicable.
For the tablet with blue LEDs condition, suppression values were significantly different than zero
at 00:00 (t(10) ¼ 15.0, p < 0.001) and at 01:00 (t(11) ¼ 16.1,p < 0.001). For the tablet-only condition,
suppression was not significantly different than zero after 1 hour exposure (t(10) ¼ 1.80, p ¼ 0.103) to
the tablet, but was significantly greater than zero after 2 hour of exposure (t(11) ¼ 3.39,p ¼ 0.006).
According to the studies(shown below in figures pg 13)of Figueiro, M., Plitnick, B., Rea, M., & Wood, B.
(2012), the calculated mean SEM (standard error of the means) CS values after 1 hour exposures were
0.46 plus or minus 0.0013 for the tablet with blue LEDs condition and 0.03 plus or minus 0.0066 for the
RUNNING HEAD: UNDERSTANDING THE EFFECTS OF LIGHT REGARDING MELATONIN 8
Figueiro (2012) concluded that even if melatonin suppression is not significant (for example
after an hour) you are still susceptible to an increased risk of diseases such as obesity (lack of sleep
makes the brain irritable and seek comfort= food). She and her team also figured that the type of task
being performed also impacts how much light is delivered to the cornea. This was proven by the team’s
dimesimeter measurements, which showed that the brightness levels varied approximately 5 lux per
activity (diff brightness levels= diff levels of repression). The team concluded exposure to compact
fluorescent lamps at 6500k suppressed melatonin the most. As a result of blocking melatonin (hormone
that induces sleep) the most, people in the 6500k setting reacted with faster reaction times because
they were more alert than others.
They also concluded that commercially available fluorescent light bulbs with different color
temperatures not only increasingly affect the circadian rhythm (a human’s 24 hour biological clock) but
also cognition or cognitive performances (because of lack of sleep). She hopes that through these
studies corporations and institutions can develop more “circadian-friendly” electronic devices. These
devices would decrease and increase contrast levels based on the time of the day (able to “tell” the time
even through bad weather conditions). Until then, she states that the best thing for people to do is limit
the amount used/time spent using electronic devices, dimming the screen as much as you can, and not
utilizing them at all before bedtime to lessen melatonin suppression.
RUNNING HEAD: UNDERSTANDING THE EFFECTS OF LIGHT REGARDING MELATONIN 9
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Figure i- Comparison between relative sleepiness/wellbeing in regards to frequency of light exposed to
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Figure ii- Supports RESULTS section of experiment (shows overall values)
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Figure iii-How the Circadian Rhythm Functions
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Figure iv-No glasses, blue melatonin supressing glasses, and orange light supressing glasses used in experiment