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It has been demonstrated that the use of social networking sites late at night can lead to sleep‐related problems that extend into the next day. A common explanation is that the light emitted from screens is disrupting the users’ circadian rhythms. An alternative explanation is that the social cognition inherent in the use of social networking sites is responsible. Here, the two factors were looked at together. Participants used Facebook on iPad tablets before sleep. This was done on different nights with two lighting conditions and with two levels of content. In the ‘light’ condition, blue wavelength light was manipulated so that it was either full wavelength or blue light filtered. In the ‘alertness’ condition, the personal significance of the content was changed from personally relevant to irrelevant. A modified version of the Pittsburgh Sleep Quality Index was used to measure sleep‐related problems. No evidence was found that simply filtering blue light or simply removing relevant content improved sleep quality. However, the two factors interacted. The results suggest that the light emitted from screens can affect sleep quality under some conditions but this is behaviourally irrelevant in the context of normal Facebook usage.
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British Journal of Psychology (2018)
©2018 The Authors. British Journal of Psychology published by
John Wiley & Sons Ltd on behalf of British Psychological Society
Facebook use and sleep quality: Light interacts with
socially induced alertness
Jenny Bowler and Patrick Bourke*
School of Psychology, University of Lincoln, UK
It has been demonstrated that the use of social networking sites late at night can lead to
sleep-related problems that extend into the next day. A common explanation is that the
light emitted from screens is disrupting the users’ circadian rhythms. An alternative
explanation is that the social cognition inherent in the use of social networking sites is
responsible. Here, the two factors were looked at together. Participants used Facebook
on iPad tablets before sleep. This was done on different nights with two lighting conditions
and with two levels of content. In the ‘light’ condition, blue wavelength light was
manipulated so that it was either full wavelength or blue light filtered. In the ‘alertness’
condition, the personal significance of the content was changed from personally relevant
to irrelevant. A modified version of the Pittsburgh Sleep Quality Index was used to
measure sleep-related problems. No evidence was found that simply filtering blue light or
simply removing relevant content improved sleep quality. However, the two factors
interacted. The results suggest that the light emitted from screens can affect sleep quality
under some conditions but this is behaviourally irrelevant in the context of normal
Facebook usage.
There is growing evidence that using laptops, tablets, and phones before going to sleep
has a detrimental effect on sleep quality. Disruptive effects have been reported in large-
scale questionnaire surveys of sleep quality (Gradisar et al., 2013; Levenson, Shensa,
Sidani, Colditz, & Primack, 2016). One explanation is that this is due to the pre-sleep
exposure to blue wavelength light emanating from screens. This inference is drawn from
physiological studies which have demonstrated that bright light in the evening inhibits the
secretion of melatonin which in turn can delay the onset of drowsiness and sleep
(Cajochen et al., 2011; Chang, Aeschbach, Duffy, & Czeisler, 2014).
It is light with short wavelengths, especially in the blue wavelength range of around
460480 nm that produce the most melatonin suppression. Cajochen et al. (2011) report
a suppression of the normal evening increase in melatonin levels when people are
exposed to a computer screen that emanates more blue light relative to one that produces
less. Similarly, Wood, Rea, Plitnick, and Figueiro (2013) found that when participants
viewed tablets through clear goggles with attached blue light-emitting diodes (LED),
melatonin increase was significantly suppressed relative to when they viewed tablets
through orange-tinted glasses that block blue light. The effect seems mediated by a
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which
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modifications or adaptations are made.
*Correspondence should be addressed to Patrick Bourke, School of Psychology, University of Lincoln, Sara Swift Building, Lincoln
LN6 7TS, UK (email:
circadian rhythm phase delay that leads to a postponement of sleep onset (Cajochen
et al., 2011). Likewise, Van der Lely et al. (2015) found that when viewing an LED
computer screen while wearing blue light-blocking glasses, melatonin levels increased
and self-perceived alertness reduced. Furthermore, Chang et al. (2014) found that light
emitted from eBooks viewed on an iPad tablet, reduced participants’ level of melatonin,
and increased their sleep latency by 10 min, compared to those participants that read a
printed book. Together, these findings show that the use of computer screens before
sleep has a direct physiological effect via the light emitted from the screen. This
suppresses the normal evening rise in melatonin; thus, it is argued, sustaining alertness,
and delaying sleep onset.
Mainstream media and device manufacturers have inferred from this that light from
screens is the cause of sleep disturbance. A corollary of this is the assumption that if
appropriate filters are used, the supposed effects on sleep quality can be mitigated ‘for
example, f.lux’ (Flux Software LLC, 2017) ‘Kids Sleep Dr’ (RMA Consulting Ltd, 2015).
However, the psychological consequences of the delay in melatonin production are far
from clear. Even the evidence for its effect on sleepiness is mixed. A recent meta-analysis
(Souman, Tinga, te Pas, van Ee, & Vlaskamp, 2018) identified a set of 28 papers that
manipulated light in the blue part of the spectrum. The results show that the relationship
with alertness is not as robust as often assumed. While some studies report strong effects,
others report no significant difference. Nonetheless, the hypothesis that light from
screens may be the factor that causes the sleep disruption reported in the survey studies
remains plausible given the clear physiological evidence of disrupted melatonin release
and independent reports that this can lead to delays in sleepiness. It is similarly plausible
that light in the blue part of the spectrum from screens has an effect on the quality of
peoples’ sleep beyond possibly delaying its onset. Existing findings of the effect of light on
sleep do not address the range of negative effects reported in survey studies, for example,
next day sleepiness and motivation. Similarly, it is far from clear whether the use of blue
light filters has any beneficial effect on sleep quality.
The content of the material viewed on computer screens before trying to sleep is a
second plausible explanation for the sleep disturbance reported in the large-scale surveys.
If the content viewed is stimulating, it will lead to alertness at a time when the alertness
system needs to be shut down (Bakoti
c & Rado
cek, 2012; Gradisar et al., 2013).
This is particularly likely in the case of Social Media use. Here, personally significant
materials are being browsed and can lead to a high arousal happy state (Arora, Broglia,
Thomas, & Taheri, 2014) or high arousal-negative states such as jealousy (Tandoc,
Ferrucci, & Duffy, 2015) and anxiety (McCord, Rodebaugh, & Levinson, 2014). More
specifically, the use of ‘Facebook’ has been found to induce a state of high arousal and high
positive valence as measured by skin conductance (Mauri, Cipresso, Balgera, Villamira, &
Riva, 2011). Facebook use has also specifically been linked to negative emotional states in
college students, that is, envy and depression (Sagioglou & Greitemeyer, 2014; Tandoc
et al., 2015). More generally, Arora et al. (2014) identified a sleep latency increase in
social network users that they attributed to the higher alertness that comes from the
interactivity and thought required. Hence, it may be the personal engagement with the
content viewed on the device that interferes with sleep, acting via the heightened
physiological state of arousal (Mauri et al., 2011) that it produces. If this is the sole cause,
the use of light filters can be expected to be ineffectual.
Whether either of these factors do account for the reports of poor sleep quality
(Gradisar et al., 2013; Levenson et al., 2016) remains an open question. Equally, whether
they could interact to produce a poorer quality of sleep is also unknown. The previous
2Jenny Bowler and Patrick Bourke
research on other aspects of sleep such as the onset of sleep and wakefulness does identify
non-additive interactions. In that case, the interactions are between the point in a
circadian rhythm and the hours since last sleep (Borb
ely, Daan, Wirz-Justice, & Deboer,
2016). Similarly, arousal and exposure to blue wavelength light may interact to affect
perception of sleep quality. Models of sleep and alertness assume a linked network by
which circadian and social cues can influence the arousal system of the brain. For
example, in the model of Saper, Scammell, and Lu (2005), the dorsomedial hypothalamic
nucleus is identified as a site of integration of circadian, social, and other cues. More
recently, Gompf et al. (2010) report links from the anterior cingulate to the locus
coeruleus arousal centre. A possible basis for an interaction seems to exist. However, the
effect of content viewed before sleep and the effect of light have tended not to be
investigated together. An exception is Higuchi, Motohashi, Liu, and Maeda (2005). Under
laboratory conditions, they studied the effects of computer gaming under two light
intensity conditions. While game playing did affect sleep latency and time spent in REM
sleep, no effect of light was found on sleep nor did light level interact with game playing
versus the control condition. The current study evaluates the impact on quality of sleep as
experienced by the users of social media, for example, next day sleepiness. Rather than
light intensity, it investigates whether the reduction in sleep quality is due to the
wavelength of light emitted from the screen, the alerting content of what is being viewed
on the device or an interaction of these two factors.
The Pittsburgh Sleep Quality Index (PSQI) was used. This is a widely utilized measure
of how people experience the quality of their sleep and is a standardized clinical measure
(Buysse, Reynolds, Monk, Berman, & Kupfer, 1989; Mollayeva et al., 2015). Participants
answer questions about different aspects of their sleep. Sleep quality is divided into seven
narrower domains. These are as follows: sleep duration, sleep disturbance, sleep onset
latency, daytime dysfunction, sleep efficiency, and overall quality. A ‘medication use’
element is also included. By the addition of the component scores, a global score of sleep
quality can be produced; the higher global scores represent poorer sleep quality. The
previous studies on the effects of electronic media use have successfully employed this
scale (Mollayeva et al., 2015).
In the current study, participants took an iPad tablet home for the duration of the
study. On different nights, participants viewed their own or a mock Facebook account,
with an amber film over the tablet screen or with no film over the tablet screen. The next
day they reflected on their sleep quality by completing a modified PSQI.
Thirty undergraduate students (21 females) aged between 18 and 23 years were recruited
and accredited for their participation. Participants were selected who routinely
used social media before sleep and who reported having a normal sleep pattern.
Participants were screened to exclude those taking antidepressants, sleep medication, or
There were four conditions. In the baseline condition, the participant viewed their real
Facebook account on a tablet with the normal settings. Alternatively, they viewed a mock
Facebook use and sleep quality 3
Facebook account (described below) on the tablet with the normal settings; their real
Facebook account on the tablet with an amber filter over the screen (described below); or
a mock Facebook account on the tablet with the amber filter over the screen. The
experiment was run over four weekday nights. The order of the conditions was pseudo-
randomized across participants within the 4-day block. A written introduction and
consent form were given to participants outlining how the study would be carried out.
Instructions were also verbally delivered, and participants’ understanding of the
instructions was checked. The instructions included the specification that depending
on condition, they were to view only their own Facebook page or the mock Facebook
page. To balance demand characteristics, for half of the participants, this included a brief
statement that ‘light level was predicted to affect the quality of sleep’, whereas for the
other half of participants, it was stated that ‘interest level was predicted to affect the
quality of sleep’. After written consent was obtained; participants received an Apple iPad
4th-generation tablet (model MD513B/A, LED-backlit screen =9.5 97.31 inches; Apple
Inc., Cupertino, CA, USA) to take home for the duration of the study (four nights).
Participants viewed Facebook either on the tablet screen with the normal settings or
with a LEE 104 deep amber filter film cut to the size of the tablet screen and attached over
the screen by a bulldog clip in each corner of the device, to filter blue light. The LEE amber
film filtered all but 018% of 460480 nm wavelength, as measured with a double-beam
scanning spectrophotometer (Lee Filters Worldwide, 2016). In the normal ‘blue light’
condition, the tablet was viewed with no film over the screen. Brightness of the tablet
screens was measured by a luminance (lux) meter (Lutron Digital Lux meter; Lx101 series,
Lutron, Taiwan). To ensure the brightness was the same for each condition, the tablets
were set to full brightness when the amber film was used (200 lux at screen level) and
brightness was lowered to match this when no film was used. The luminance of each
tablet was also checked after each participant returned the tablet. Hence, blue light
wavelength transmission was altered but brightness (lux) was kept the same for each
The stimulating/arousing condition had two levels: a ‘high arousal’ level, where the
participant’s own Facebook account was viewed and a ‘low arousal’ level where the
participant viewed a mock Facebook account. The mock Facebook account was a profile
set up for this study; this profile contained no photographs or ‘friends’ for users to contact.
The profile included 53 ‘liked’ pages of companies that were not targeted to the
participant’s age range, for example, Fisher-price toys. Most users report their screen time
exposure before sleep as either <15 min or <30 min (Moulin & Chung, 2017; Nordnes,
Storemark, Bjorvatn, & Pallesen, 2014). Each night participants were instructed to view
either their own or the mock Facebook account for 1530 min in the hour before bed. To
minimize disruption to participants’ normal evening FaceTime viewing routine, they
were not asked to change what they did in the rest of the hour before sleep. Participants
were instructed to do the study in a dark environment with the curtains closed and no
other lights on, so the only light in the room was from the tablet screen. They were asked
to not change the brightness settings of the screen. They were asked to hold the device at a
comfortable viewing distance. To minimize disruption to their FaceTime viewing routine,
participants were trusted to follow the instructions, without further checks.
The next morning a modified version of the PSQI (described below), was completed by
the participant to assess their sleep on the previous night. Exceptions were questions
which dealt with daytime experience (questions 8, 9, 10) which were completed the
following evening. On completion of the study, participants received a written debrief,
this fully explained the true aim of the experiment, that is, to assess whether the quality of
4Jenny Bowler and Patrick Bourke
sleep may be reduced by the arousing content, the light emitted from the screen, or both.
At this session, they were also asked about how interesting they found the mock Facebook
condition and their ability to comply with the instructions.
A small modification was made to the standard PSQI questions. This was required as
the standard PSQI measures sleep quality over the previous month, and the current study
wished to measure sleep quality after each night. So, questions were changed from asking
about sleep over the previous month to sleep over the previous night. For example,
question 6 ‘During the past month, how would you rate your quality of sleep overall?’ was
altered to ‘During the previous night how would you rate your sleep quality overall?’ This
was the only change necessary for questions 1, 2, 3, 4, 6, 9 and 10 which addressed
bedtime, time to fall asleep, time of rising, actual hours of sleep, and sleep quality. Three of
the PSQI questions (5, 7, 8) ask about frequency of occurrence over the previous month;
not occurred, less than once a week, once or twice a week, and three or more times a
week. These were changed to yes/no answer questions; not occurred, occurred. These
questions dealt with trouble sleeping, medication used, and trouble staying awake.
This study received ethical approval from the University of Lincoln, Psychology Research
Ethics Committee.
Data analyses
The individual questions scores were used to compute standard subcomponent scores.
The components were duration, disturbance, latency, daytime dysfunction, efficiency,
quality, and hypnotics used. Scores could range from 0 to 3 for the seven components of
sleep tested, which totalled to produce a global modified PSQI score (range of 021) for
each questionnaire. The lower the global modified PSQI score, or score for any
component, the better the quality of sleep.
Participants’ modified global PSQI scores are shown in Figure 1.
At debrief, participants confirmed that while they did not find the mock Facebook page
interesting, they were able to follow the instruction of viewing for 1530 min.
The results were analysed by a 2 92 within-subjects ANOVA. This dealt with self-
reported sleep quality for the factors ‘arousal level’ (high arousal or low arousal content)
and ‘light’ (blue light or filtered blue light). The results show no significant main effect of
arousal level, F(1, 29) =2.60, p=.118, g2
p=.082, or light, F(1, 29) =1.39, p=.247,
p=.046. However, there was a significant interaction between arousal level and light
level, F(1, 29) =6.867, p=.014, g2
p=.191. The interaction (see Figure 1) shows that the
best sleep quality was obtained for the night condition of ‘blue-filtered light’ and ‘low
arousal’ relative to the other three nights.
To further explore which components of sleep quality were the most affected, 2 92
within-subject ANOVAs were conducted on the components of the PSQI. There were no
main effects. The results show a significant interaction of arousal level and light level for
the components of sleep duration, F(1, 29) =5.66, p<.05, g2
p=.163, sleep onset
latency, F(1, 29) =7.10, p<.05, g2
p=.197, and daytime activity dysfunction on the
Facebook use and sleep quality 5
following day, F(1, 29) =6.99, p<.05, g2
p=.192. Like the main analysis, these different
aspects of sleep quality were all best in the ‘low arousal-no blue light’ condition. In
contrast, no significant interactions were found for the components of sleep disturbance,
F(1, 29) =0.05, p>.05, g2
p=.002, sleep efficiency, F(1, 29) =0.86, p>.05, g2
or sleep quality overall, F(1, 29) =0.71, p>.05, g2
p=.024. The component of
medication was not analysed as use of medication was in the participant exclusion criteria.
To test whether the instructions affected the reporting of sleep quality, instructions
was added as a between subjects factor. There was no main effect, F(1, 28) =.21, p=.65,
p=.007, nor any interaction effect; with ‘light’, F(1, 28) =.22, p=.65, g2
‘arousal level’, F(1, 28) =2.43, p=.13, g2
p=.08, or ‘light’ by ‘arousal level’,
F(1, 28) =.42, p=.52, g2
p=.015. The same pattern was found for each of the
components of sleep, there were no significant main effects of instructions, nor did
instruction interact with the other two factors.
The effect of pre-sleep Facebook use on sleep quality was measured using a self-report of
aspects of the previous night’s sleep (the modified PSQI). Two potentially disrupting
factors were manipulated; the wavelength composition of the light emitted from the
screen and the personal interest of the content that was being viewed. The factors
interacted so that superior quality sleep was only reported when a non-personal Facebook
account was viewed in blue-filtered light. At a practical level, the results suggest that the
use of blue light filters is unlikely to be effective when viewing Facebook under normal
Figure 1. Effect of arousal and blue wavelength filtered light on sleep quality. In the high arousal
conditions, participants viewed their own Facebook account; in the low arousal conditions, they viewed a
mock Facebook account. Screens were either viewed with (full light) or with a blue wavelength filter.
Poor/Good sleep is as measured on the modified Pittsburgh Sleep Quality Index. Lower numbers indicate
higher quality of sleep. One standard error bars are shown.
6Jenny Bowler and Patrick Bourke
viewing conditions. The results further show that under normal lighting conditions, the
content of Facebook pages, at least as varied in this study, does not affect sleep quality.
The wavelength of light can have an effect on how people perceived the quality of the ir
sleep. Previous work had shown a significant circadian rhythm phase delay in the release
of melatonin (Chang et al., 2014; Van der Lely et al., 2015). The present results indicate
that this physiological effect is visible at a wide behavioural level (i.e., sleep quality,
daytime activity dysfunction) but only when the content viewed is ‘low arousing’. This is
consistent with Van der Lely et al. (2015) whose participants were tested under
conditions that can be considered ‘low arousal’. These participants spent 3 hrs in front of
a bright monitor with relatively little interruption (mainly half hourly interruptions to
measure sleepiness and to collect saliva). In the condition where blue wavelength light
was blocked, a drop in vigilance was reported as was an increased sense of sleepiness.
The current results provide additional information on the length of exposure
necessary and the percentage of blue wavelength light needed to effect sleep. Expanding
on existing results (Cajochen et al., 2011; Gringras, Middleton, Skene, & Revell, 2015;
Tandoc et al., 2015; Van der Lely et al., 2015), the current study has found that even a
brief 15- to 30-min exposure can be sufficient to produce a significant difference in sleep
quality, when arousal level is low. This is considerably shorter than that typically known
from previous studies, 3 hrs (Van der Lely et al., 2015), 4 hrs (Chang et al., 2014), 5 hrs
(Cajochen et al., 2011), and 2 hrs (Wood et al., 2013). However, that effects can be seen
this quickly is indicated by Horne, Donlon, and Arendt (1991). The amount of blue light
that needs to be filtered to enhance sleep quality is also indicated by the current results.
The use of a tinted LEE filter in the ‘no blue light’ level reduced the blue light emitted from
the screen to 018% in the 460480 nm wavelength range . This transmission rate is higher
than that used in other studies. For example, the glasses utilized in the study by Van der
Lely et al. (2015) transmitted 1.72% and the glasses utilized by Wood et al. (2013)
transmitted 0% of light at 460480 nm. The level filtered in the current study was
adequate to enhance sleep quality when viewing low arousing content. However, this
does raise the question of whether the same result would be seen with a more complete
blocking of blue light.
Filtering the wavelength of light was only effective in our ‘low arousing’ condition.
This raises the question of what it is about the material or activity that makes it ‘low
arousing’? The material was designed to be unexciting and uninteresting. However, this
may not be the critical factor. Our ‘low arousing’ condition inevitably avoided social
cognition and interaction (jealousy, envy, happiness). It may be this lack of personal
significance that makes out stimuli ‘low arousing. This view seems sensible when a
comparison with Chang et al. (2014) is made. In that study, participants supplied their
own reading material and it had to be ‘pleasure’ or ‘leisure’ reading material. They report
greater sleepiness when reading a printed book in dim light relative to reading an Ebook.
Clearly here the activity is not dull or uninteresting but nonetheless, a similar
‘wakefulness’ in normal screen light and ‘sleepiness’ in dim light is seen. It may well be
that so long as people do not have to involve themselves with the worries, concerns, and
issues of their lives (McCord et al., 2014; Tandoc et al., 2015) sleep will be undisrupted;
the stimuli will be ‘low arousal’.
The global disruption of sleep quality can be better understood by examining which
aspects of sleep were and were not disrupted. The sleep onset latency component of the
PSQI is disrupted, consistent with the studies showing a delay in melatonin release when
viewing a screen in the evening, and this delay may also explain why total sleep duration is
shorter. It is interesting to note that while participants report no awareness of any
Facebook use and sleep quality 7
difference in their quality of sleep across the conditions, they nonetheless experienced an
effect the next day of daytime dysfunction (the impact on staying awake or getting up
enough enthusiasm to get things done the next day).
There are some specific methodological issues that deserve consideration. The first is
whether the study had sufficient power to detect main effects of ‘Light’ or ‘Arousal’ if they
were there. The effect of light in the blue part of the spectrum on sleepiness is not as
robust as often assumed (Souman et al., 2018). Nonetheless, given that earlier studies
(Cajochen et al., 2011) have shown that filtering blue light changes melatonin levels and
can change measures of sleepiness, the credibility of the null result of varying the light is
worth further consideration. Sample size had been chosen based on previous studies
using the PSQI (Gross, Kreitzer, Russas, & Treesak, 2004; Lai & Good, 2005; Sun, Kang,
Wang, & Zeng, 2013; Yook et al., 2008). However, to explore whether the study had
sufficient power, a power analysis with the program G*Power (Faul, Erdfelder, Lang, &
Buchner, 2007) was conducted to evaluate sample sizes sufficient to detect changes in
sleep quality. Given an alpha of p<.05, desired power of .90 and moderate effect sizes
(0.06) gives a power of .91 for a sample size of 30 participants. It seems likely therefore
that the current study had sufficient power to detect differences had they existed.
Nonetheless, it remains possible that the effect sizes were small and would not have been
detected. This is plausible given the large proportion of studies that did not find a
significant effect of manipulating the blue light content of the spectrum (Souman et al.,
2018). If so then the sample sizes would have had to be considerably larger. Souman et al.
(2018) suggest a sample of n>155. This would be a more reliable sample if the effect sizes
are indeed small. Assuming moderate effect sizes, it seems reasonable to interpret the lack
of significant difference between the ‘Light’ conditions and between ‘Arousal’ conditions
as indicating that there were no simple ‘Filtered light’ or ‘Arousal’ effects.
A second methodological issue relates to the variability allowed to participants’
viewing time. An important consideration in the design of this study was ensuring that
participants were fully engaged in the social media experience in the intended arousing
condition. For this reason, they were allowed to use any time between 15 and 30 min, that
is, they could switch off the tablet if it was no longer interesting to them. While this is likely
to have succeeded in ensuring socially induced high arousal throughout this condition, it
does allow some variation in viewing time. It is possible that participants spent the
shortest time viewing screens in the Low Arousal +Blue-Filtered-Light condition. This
could happen with the reasonable assumption that people viewed the low arousal pages
for less time (as they are boring) and that in blue-filtered light, they also viewed the display
for less time (as they become drowsy). This could produce an alternative explanation.
Rather than supposing that the effect on sleep quality is due to blue light filtering, it might
instead arise from differing light exposure durations, that is, 15 min versus 30 min. It is
known that full-spectrum light exposure can affect alertness (Souman et al., 2018). One
study (Cajochen, Zeitzer, Czeisler, & Dijk, 2000) has looked systematically at the effect of
duration of light exposure. They showed that the longer participants were exposed to full-
spectrum light, the greater were the effects on alertness and sleep. However, as Cajochen
et al. (2000) made recordings every 30 min whether such effects would be seen with only
a 15-min difference in light exposure is unknown from this study. No difference in
subjective alertness was seen until after two hours exposure to very bright light (3,190
lux) compared to very dull light (23 lux). Souman et al. (2018) report eight studies that
have looked at subjective alerting effects for shorter durations where full-spectrum light
was used at differing intensities. With exposures of 30 min, effects on alertness are
reported in six of the studies and no effect in the remaining two studies. However, as these
8Jenny Bowler and Patrick Bourke
studies used extreme brightness (thousands of lux), it is difficult to relate them to the
current case where light intensity from a screen is low (200 lux). The one study (R
Gordijn, Beersma, de Vries, & Daan, 2005) that used a low illumination (100 lux)
compared to very low (<10) found no effects after 4 hrs. The mixed nature of these results
leaves open the real possibility that sleepiness could be affected by 15 min shorter light
exposure. This then highlights a confound in the current study and presents a possible
alternative explanation for the current results. These factors could be separated in future
experimentation. One strategy might be to match the exposure duration to that
spontaneously used by a given participant when viewing Facebook before going to sleep.
It would also be important to monitor behaviours around bedtime to ensure that there was
no systematic variation in light exposure or activity. This could be done with a
combination of technical measures, self-report, and by the wearing of ActiGraphs or other
commercially available sleep and activity ‘watches’.
Finally, there is the issue of demand effects. Two alternative sets of instructions were
used to control this, half were led to believe that light wavelength but not content would
affect sleep, and the other half the opposite. These alternative instructions had no effect. A
more sophisticated expectation effect might be that participants guessed that dull light
and boring material would improve sleep quality. If so this may have affected how they
reported and so explain the pattern observed. However, such demand effects seem
unlikely. Participants may have adopted an equally plausible alternative. They might have
guessed that sleep quality would be worse after looking at exciting pages in full light. Most
participants would have had to have adopted the same assumption for any statistically
significant effect to emerge. There seems no obvious reason to think they would all opt for
the first over the second. Indeed, the possibility that the results could be due to
participants making an educated guess at the hypotheses is further weakened by the lack
of a consistent effect on the subscales. If they really thought that filtered light and boring
material produced better sleep, then they would be likely to report this consistently. They
would likely report less disruption the next day, longer time asleep, quicker time to get to
sleep, less next day disruption, less sleep disturbance, more time spent sleeping when in
bed, and indeed a higher explicit rating of their sleep quality. In fact, only the first three
showed any effect.
The practical issue of the everyday sleep quality of young adults who engage with
Facebook before sleep was addressed. Evidence was found for some diminution of sleep
quality (including next day functioning) when engaged in normal Facebook use. This did
not improve when a blue light filter was placed over the screen, suggesting that when
viewing social media, filters may not be as effective as sometimes assumed. However,
there is some indication that filtering short wavelength light can have an effect on sleep
quality but this seems only to be visible when the content viewed is non-arousing. Further
work is needed particularly to understand this apparent interaction.
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... Also, higher level of mobile phone dependency may result in a higher level of psychological stress or arousal, which may disturb the sleep40,41 . In addition, it is reported that the blue light emitted from the mobile phone screen may in uence the melatonin levels and affect sleep process42 . ...
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Objective The purpose of the study was to examine the associations between mobile phone dependency and sleep quality among college students during COVID-19 outbreak. The potential mediation roles of bedtime procrastination and fear of missing out (FoMO) were investigated. Methods A total of 881 college students completed an online survey in May 2022 in Shanghai, China. Mobile Phone Involvement Questionnaire, Bedtime Procrastination Scale, Bedtime Procrastination Scale and Pittsburgh Sleep Quality Index were used to assess mobile phone dependency, bedtime procrastination, fear of missing out, and sleep quality, respectively. Multiple linear regression and mediation analysis were conducted. Results The correlation analyses indicated mobile phone dependency was positively associated with fear of missing out, bedtime procrastination, and sleep quality among college students. The structural equation modeling analyses revealed that mobile phone dependency had significant indirect effects on sleep quality through bedtime procrastination (indirect effect: 0.030, 95%CI: 0.022–0.041) and fear of missing out (indirect effect: 0.013, 95%CI: 0.003–0.023). Conclusion The findings indicated that bedtime procrastination and fear of missing out partially mediated on the association between mobile phone dependency and sleep quality. Bedtime procrastination and fear of missing out should be considered as potential intervention targets for reducing mobile phone dependency and improving sleep quality in college students.
... Die in dieser Übersichtsarbeit gefundenen Studien zum Einfluss von hellem Licht vor dem Zubettgehen zeigen je doch heterogene Ergebnisse. Während manche Autor_in nen über keinen Einfluss von Bildschirmhelligkeiten oder den kurzwelligen (blauen) Farbanteilen von Bildschirmen berichteten (Higuchi et al., 2005;Jones et al., 2018;Bowler & Bourke, 2019;Smidt et al., 2021), konnten andere Au tor_innen in ihren Studien aufzeigen, dass der übermäßige Konsum von zu hellem oder bläulichem Licht vor dem Zubettgehen zu erhöhter Wachheit und folglich zu einer verlängerten Einschlafdauer führt Chang et al., 2015;Van der Lely et al., 2015). ...
Zusammenfassung. Hintergrund: Die Nutzung elektronischer Geräte und der damit verbundenen Bildschirmzeit nahm in den letzten Jahren stetig zu. Kognitive und emotionale Erregung durch Bildschirminhalte, spätere Zubettgehzeiten durch eine intensive abendliche Nutzung von elektronischen Geräten sowie die generelle aktivierende Wirkung des Bildschirmlichts können den Schlaf und die schulischen Leistungen von Kindern und Jugendlichen stark beeinflussen. Methoden: Das Ziel dieser Übersichtsarbeit ist es, den aktuellen Forschungsstand zum Einfluss der Nutzung verschiedener elektronischer Geräte auf den Schlaf und die Lernleistungen bei Kindern und Jugendlichen zusammenzufassen. Zusätzlich wurde eine systematische Literaturrecherche zu Auswirkungen der Lichtemission von Bildschirmen auf den Schlaf und die schulischen Leistungen am nächsten Tag in elektronischen Datenbanken durchgeführt. Ergebnisse: Die abendliche Bildschirmnutzung wirkt sich in vielerlei Hinsicht negativ auf den Schlaf (z.B. kürzere Schlafdauer und verlängerte Schlaflatenz) und in der Folge auf die Lernleistung von Kindern und Jugendlichen aus, wobei der direkte Einfluss des von den elektronischen Geräten emittierten Lichtes auf den Schlaf oder die Lernleistung bei Kindern und Jugendlichen noch kontrovers diskutiert wird. Diskussion: Eine Einschränkung der Bildschirmnutzung am Abend ist ein vielversprechender Ansatz zur Verbesserung der Schlafqualität und kognitiven Leistung bei Kindern und Jugendlichen.
... Professionals may take preventive actions in helping the students from bearing too much cognitive workload and in reducing loneliness. According to a report, Facebook use and internet addiction have been linked to high sleep quality issues (Bowler & Bourke, 2019). It is important to investigate the relationships as students sleep are vital because of its significant effects on the development of important psychophysiological functions, including behavior, emotions, and attention (Kootesh et al., 2016). ...
... A further home-based study in undergraduate students showed no main effects for tablet light exposure (unfiltered [< 200 lux] or short-wavelength filtered light [200 lux]) or stimulation level (participant's Facebook account versus a sham Facebook account designed to be unstimulating), but found that the shortwavelength filtered and low stimulation condition was associated with significantly better self-reported sleep quality, sleep duration, sleep onset latency, and daytime function relative to the other conditions [76]. The pattern of findings suggests that engaging in stimulating tasks while using electronic devices before bed disrupts sleep regardless of spectrum, but only the modification of stimulation level and light spectrum in tandem is associated with improved subjective sleep and daytime functioning. ...
Light is a potent circadian entraining agent. For many people, daily light exposure is fundamentally dysregulated with reduced light during the day and increased light into the late evening. This lighting schedule promotes chronic disruption to circadian physiology resulting in a myriad of impairments. Developmental changes in sleep-wake physiology suggest that such light exposure patterns may be particularly disruptive for adolescents and further compounded by lifestyle factors such as early school start times. This narrative review describes evidence that reduced light exposure during the school day delays the circadian clock, and longer exposure durations to light-emitting electronic devices in the evening suppress melatonin. While home lighting in the evening can suppress melatonin secretion and delay circadian phase, the patterning of light exposure across the day and evening can have moderating effects. Photic countermeasures may be flexibly and scalably implemented to support sleep-wake health; including manipulations of light intensity, spectra, duration and delivery modality across multiple contexts. An integrative approach addressing physiology, attitudes, and behaviors will support optimization of light-driven sleep-wake outcomes in adolescents.
Despite much attention on digital media use and young peoples’ sleep, the literature on digital media and its impact on sleep in older adolescents and young adults remains to be synthesized. We conducted a systematic review of studies including young people aged 16–25 years. We searched Medline, Web of Science, and CINAHL for observational studies, identifying 60 studies. These studies were assessed for methodological quality. Only studies rated as moderate or high-quality studies were included (n = 42). A narrative synthesis summarized the impact of digital media use on eight sleep outcomes: Bedtime; Sleep onset latency or problems falling asleep; Sleep duration; Early awakening; Sleep disturbance; Daytime tiredness and function; Sleep deficits; Sleep quality. In summary, digital media use was associated to shorter sleep duration and poorer sleep quality. These associations were found for general screen use and use of mobile phone, computer, internet, and social media, but not for television, game console, and tablet use. Most studies investigating bedtime or nighttime use found associations to poor sleep outcomes. Later bedtime and daytime tiredness were associated with mobile phone use at night. Additional research is warranted to draw solid conclusions about the causal direction and to understand the underlying mechanisms.
Content-Marketing, also die Planung, Produktion und Distribution von zielgruppen-adäquaten Inhalten, hat insbesondere durch Social Media nochmals an Bedeutung gewonnen. Im Hinblick auf die enorme Menge an Inhalten, die auf Nutzer konstant einwirken, ist es für Unternehmen immer schwieriger, die Aufmerksamkeit der Nutzer zu gewinnen. Nur Inhalte, die den Wünschen der Nutzer entsprechen und diesen in irgendeiner Form einen Mehrwert bieten, haben die Chance, zur Erfüllung von Kommunikationszielen von Unternehmen beizutragen. Die Bereitstellung derartiger Inhalte setzt einen sinnvollen (Planungs-)Prozess voraus. Das vorliegende Buch bietet Praktikern und Studierenden einen Überblick über die verschiedenen Bereiche eines Content-Marketing.
Screen media technology (SMT) use has become increasingly prevalent among youth, and is associated with a variety of negative outcomes, including poor sleep and impairments in several domains of cognitive functioning, including task-switching, attention, working memory, and response inhibition. Youth with ADHD may be particularly vulnerable to the hazards of SMT use and engage in problematic screentime behaviors at disproportionate rates. SMT may result in negative outcomes for individuals with ADHD via several processes, including: (a) screen characteristics, nighttime use, and interference with sleep, (b) media multitasking, (c) device notifications, (d) media content, and (e) compulsive SMT use. Despite the harmful effects of SMT use, digital therapeutics, such as serious game interventions, SMS interventions, and smartphone applications, have demonstrated promise in improving ADHD symptoms and enhancing medication treatment adherence in youth with ADHD. Several unknowns currently exist in relation to the effects of SMT use in children and adolescents with ADHD. Research should focus on disentangling the directionality and strength of the relationship between SMT use and ADHD-related symptoms, along with individual-level factors related to harmful SMT use, such as sociodemographic background. Further research using longitudinal designs and objective measurements of SMT use is needed to better understand the effect of screen-based behaviors on the mental and physical wellbeing of youth with ADHD and to pinpoint potential intervention targets. Parental mediation strategies, such as autonomy-supportive mediation, may be an effective strategy for mitigating the hazardous effects of SMT use in this population.
Athletes display differing sleep habits to non-athletic populations; similarly, differences occur in sleep habits between athletes from different sports. There is currently limited research investigating the differences in sleep habits and behaviors between different levels of competition within the same sport. A total of 224 rugby union athletes (109 academy, 38 semi-professional, 84 professional) completed the Athlete Sleep Behavior Questionnaire and the Pittsburgh Sleep Quality Index. Professional athletes displayed a significantly longer self-reported sleep duration compared to semi-professional and academy athletes (7 h 52 min ± 51 min vs. 7 h 16 min ± 1 h 15 min vs. 7 h 19 min ± 1 h 12 min, p < 0.01). Pittsburgh Sleep Quality Index global scores revealed a significantly lower ( p = 0.04, d = 0.3) score for professional athletes (5.2 ± 2.5 AU) than academy athletes (6.0 ± 2.7 AU). Individual components of the Pittsburgh Sleep Quality Index revealed significant differences ( p < 0.05) between groups for sleep duration and daytime dysfunction. No significant differences ( p > 0.05) were observed between levels of competition for the Athlete Sleep Behavior Questionnaire global score; however, significant differences ( p < 0.05) were observed for 6 of the 18 items. This study was the first to investigate sleep behaviors across multiple levels of competition in rugby union athletes. Professional athletes displayed longer sleep duration compared to semi-professional and academy level athletes. Additionally, results highlighted that differences exist between levels of competition for specific sleep behaviors. This study identified that sleep behaviors could be improved for all levels of rugby union athletes.
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Introduction: Blue light from electronic devices has a bad reputation. It has a wavelength which may influence our circadian rhythm and cause bad sleep. But there are other aspects of blue light exposure which are often overlooked, for example, it may influence performance and wellbeing. However, few resources summarize its effects systematically. Therefore, the goal of this systematic review was to distil the present evidence on blue light exposure and its influence on sleep, performance and wellbeing and discuss its significance for athletes. Methods: The databases that were searched were Cochrane, Embase, Pubmed, Scopus, and Virtual Health Library. The studies included investigated the influence of blue light exposure on either sleep, performance, wellbeing or a combination of those parameters on healthy humans. Quality assessment was done based on the quantitative assessment tool “QualSyst.” Results: Summarizing the influence of blue light exposure, the following results were found (expressed as proportion to the number of studies investigating the particular parameter): Fifty percent of studies found tiredness to be decreased. One fifth of studies found sleep quality to be decreased and one third found sleep duration to be decreased. Half of the studies found sleep efficacy to be decreased and slightly less than half found sleep latency to be increased. More than one half of the studies found cognitive performance to be increased. Slightly more than two thirds found alertness to be increased and reaction time to be decreased. Slightly less than half of the studies found wellbeing to be increased. Conclusion: Blue light exposure can positively affect cognitive performance, alertness, and reaction time. This might benefit sports reliant on team-work and decision-making and may help prevent injury. Blue light might also have negative effects such as the decrease in sleep quality and sleep duration, which might worsen an athlete’s physical and cognitive performance and recovery. Further research should explore if blue light can improve sleep, performance and wellbeing to significantly benefit athletic performance.
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People are more and more using social networking sites (SNSs) like Facebook and MySpace to engage with others. The use of SNSs can have both positive and negative effect on the individual; however, the increasing use of SNSs might reveal that people look for SNSs because they have a positive experience when they use them. Few studies have tried to identify which particular aspects of the social networking experience make SNSs so successful. In this study we focus on the affective experience evoked by SNSs. In particular, we explore whether the use of SNSs elicits a specific psychophysiological pattern. Specifically, we recorded skin conductance, blood volume pulse, electroencephalogram, electromyography, respiratory activity, and pupil dilation in 30 healthy subjects during a 3-minute exposure to (a) a slide show of natural panoramas (relaxation condition), (b) the subject's personal Facebook account, and (c) a Stroop and mathematical task (stress condition). Statistical analysis of the psychophysiological data and pupil dilation indicates that the Facebook experience was significantly different from stress and relaxation on many linear and spectral indices of somatic activity. Moreover, the biological signals revealed that Facebook use can evoke a psychophysiological state characterized by high positive valence and high arousal (Core Flow State). These findings support the hypothesis that the successful spread of SNSs might be associated with a specific positive affective state experienced by users when they use their SNSs account.
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The purpose of this research study was to explore with what impact evening media use interfered with either schoolwork and/or sufficient healthy sleep. In addition, the study examined with what impact there may be a compromise in students’ ability or aptitude for positive academic success, related to either lack of sleep or electronic media use. The participants were 89 high school and college students, ages 16 through 25, with median age of 18. Research was conducted using a secured online survey tool. Electronic habits, internet and social networking usage, sleep and rise times, daily sleepiness and perceptions were examined. College students were randomly sampled and participated in an in-depth, one-time survey. High school students participated in a weeklong nightly electronic sleep & evening media use survey and journal. Data was obtained from anonymous and coded student responses and student and teacher surveys. The results of the study suggested that healthful adolescent sleep is indeed greatly compromised, during a time when the reverse is vitally important. Of students randomly sampled, all but one student owned a cell phone. In the total study group, a majority were smart phone owner-users (84%). Many high school participants slept with a cell phone or tablet in their bed (72%), and among college participants who regularly slept with cell phone, tablet, or laptop, this rose to 86%. Over half of these students continued to access and use their devices in bed for significant amounts of time prior to sleeping. Many of these even awakened after falling asleep to access or respond to electronic messaging. The research indicated that unhealthy sleep habits may be creating a generation of sleep-deprived individuals who may not be functioning at top capacity. Findings regarding a correlation between lack of sleep and quantified academic success are inconclusive, however, student perceptions indicate that they believe there is a relationship. Findings also suggest that all instructors of late adolescent students aged 16-25 may count on the fact of their student clientele owning and using mobile devices to access internet for social purposes. Students allow their social digital world to impede and compete with their academic time and biological sleep cycle. Instructors would be wise to appropriately channel the digital skills of this new generation of no longer-wired, but now “wi-fied” students. Therefore it is strongly suggested that teachers, parents, and medical personnel adopt and provide healthy guidelines for parents to use with pre-teens and teens, to facilitate and develop in the next generation of students some structure and means of protecting their health in the realms of electronics and sleep.
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In the last three decades the two-process model of sleep regulation has served as a major conceptual framework in sleep research. It has been applied widely in studies on fatigue and performance and to dissect individual differences in sleep regulation. The model posits that a homeostatic process (Process S) interacts with a process controlled by the circadian pacemaker (Process C), with time-courses derived from physiological and behavioural variables. The model simulates successfully the timing and intensity of sleep in diverse experimental protocols. Electrophysiological recordings from the suprachiasmatic nuclei (SCN) suggest that S and C interact continuously. Oscillators outside the SCN that are linked to energy metabolism are evident in SCN-lesioned arrhythmic animals subjected to restricted feeding or methamphetamine administration, as well as in human subjects during internal desynchronization. In intact animals these peripheral oscillators may dissociate from the central pacemaker rhythm. A sleep/fast and wake/feed phase segregate antagonistic anabolic and catabolic metabolic processes in peripheral tissues. A deficiency of Process S was proposed to account for both depressive sleep disturbances and the antidepressant effect of sleep deprivation. The model supported the development of novel non-pharmacological treatment paradigms in psychiatry, based on manipulating circadian phase, sleep and light exposure. In conclusion, the model remains conceptually useful for promoting the integration of sleep and circadian rhythm research. Sleep appears to have not only a short-term, use-dependent function; it also serves to enforce rest and fasting, thereby supporting the optimization of metabolic processes at the appropriate phase of the 24-h cycle.
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Objective In an effort to enhance the efficiency, brightness and contrast of light-emitting (LE) devices during the day, displays often generate substantial short-wavelength (blue-enriched) light emissions that can adversely affect sleep. We set out to verify the extent of such short-wavelength emissions, produced by a tablet (iPad Air), e-reader (Kindle Paperwhite 1st generation) and smartphone (iPhone 5s) and to determine the impact of strategies designed to reduce these light emissions. SettingUniversity of Surrey dedicated chronobiology facility.Methods Firstly, the spectral power of all the light-emitting (LE) devices was assessed when displaying identical text. Secondly, we compared the text output with that of ‘Angry Birds’-a popular top 100 ‘App Store’ game. Finally we measured the impact of two strategies that attempt to reduce the output of short-wavelength light emissions. The first strategy employed an inexpensive commercially available pair of orange-tinted ‘blue-blocking’ glasses. The second tested an app designed to be ‘sleep-aware’ whose designers deliberately attempted to reduce blue-enriched light emissions.ResultsAll the LE devices shared very similar enhanced blue-light peaks when displaying text. This included the output from the backlit Kindle Paperwhite device. The spectra when comparing text to the Angry Birds game were also very similar, although the
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This review appraises the process of development and the measurement properties of the Pittsburgh sleep quality index (PSQI), gauging its potential as a screening tool for sleep dysfunction in non-clinical and clinical samples; it also compares non-clinical and clinical populations in terms of PSQI scores. MEDLINE, Embase, PsycINFO, and HAPI databases were searched. Critical appraisal of studies of measurement properties was performed using COSMIN. Of 37 reviewed studies, 22 examined construct validity, 19 - known-group validity, 15 - internal consistency, and three - test-retest reliability. Study quality ranged from poor to excellent, with the majority designated fair. Internal consistency, based on Cronbach's alpha, was good. Discrepancies were observed in factor analytic studies. In non-clinical and clinical samples with known differences in sleep quality, the PSQI global scores and all subscale scores, with the exception of sleep disturbance, differed significantly. The best evidence synthesis for the PSQI showed strong reliability and validity, and moderate structural validity in a variety of samples, suggesting the tool fulfills its intended utility. A taxonometric analysis can contribute to better understanding of sleep dysfunction as either a dichotomous or continuous construct. Copyright © 2015 Elsevier Ltd. All rights reserved.
Periodic, well timed exposure to light is important for our health and wellbeing. Light, in particular in the blue part of the spectrum, is thought to affect alertness both indirectly, by modifying circadian rhythms, and directly, giving rise to acute effects. We performed a systematic review of empirical studies on direct, acute effects of light on alertness to evaluate the reliability of these effects and to assess to what extent they depend on other factors, such as time of day, exposure duration and sleep pressure. In total, we identified 74 studies in which either light intensity, spectral distribution, or both were manipulated, and the effects on behavioral measures of alertness were evaluated, either subjectively or measured in performance tasks. The results show that increasing the intensity or the color temperature of polychromatic white light in general has been found to increase subjective ratings of alertness, though a substantial proportion of these studies failed to find significant effects. There is little evidence in the literature that these subjective alerting effects of light also translate into improvements on performance measures of alertness. For monochromatic or narrowband light exposure, some studies have shown improvement in reaction time tasks with exposure to blue light, but generally this was not accompanied by changes in subjective alertness. Thus, the alerting effects of light are far less clear than often suggested. We suggest that in future studies more attention should be paid to other factors that may influence the effects of light, such as chronotype, circadian phase, homeostatic state and prior light history.
This review appraises the process of development and the measurement properties of the Pittsburgh sleep quality index (PSQI), gauging it’s potential as a screening tool for sleep dysfunction in non-clinical and clinical populations; it also compares non-clinical and clinical populations in terms of PSQI scores. MEDLINE, EMBASE, PsycINFO, and HAPI databases were searched. Critical appraisal of measurement properties was performed using COSMIN. Of 37 reviewed studies, 22 examined construct validity, 19 - known-group validity, 15 - internal consistency, and three - test-retest reliability. Study quality ranged from poor to excellent, with the majority designated fair. Internal consistency, based on Cronbach’s alpha, was good. Discrepancies were observed in factor analytic studies. In non-clinical and clinical samples with known differences in sleep quality, the PSQI global scores and all subscale scores, with the exception of sleep disturbance, differed significantly. The best evidence synthesis for the PSQI showed strong reliability and validity, and moderate structural validity in a variety of samples, suggesting the tool fulfills its intended utility. A taxonometric analysis can contribute to better understanding of sleep dysfunction as either a dichotomous or continuous construct.
Introduction: Many factors contribute to sleep disturbance among young adults. Social media (SM) use is increasing rapidly, and little is known regarding its association with sleep disturbance. Methods: In 2014 we assessed a nationally-representative sample of 1788U.S. young adults ages 19-32. SM volume and frequency were assessed by self-reported minutes per day spent on SM (volume) and visits per week (frequency) using items adapted from the Pew Internet Research Questionnaire. We assessed sleep disturbance using the brief Patient-Reported Outcomes Measurement Information System (PROMIS®) Sleep Disturbance measure. Analyses performed in Pittsburgh utilized chi-square tests and ordered logistic regression using sample weights in order to estimate effects for the total U.S. Population: Results: In models that adjusted for all sociodemographic covariates, participants with higher SM use volume and frequency had significantly greater odds of having sleep disturbance. For example, compared with those in the lowest quartile of SM use per day, those in the highest quartile had an AOR of 1.95 (95% CI=1.37-2.79) for sleep disturbance. Similarly, compared with those in the lowest quartile of SM use frequency per week, those in the highest quartile had an AOR of 2.92 (95% CI=1.97-4.32) for sleep disturbance. Associations all demonstrated a significant linear trend. Discussion: The strong association between SM use and sleep disturbance has important clinical implications for the health and well-being of young adults. Future work should aim to assess directionality and to better understand the influence of contextual factors associated with SM use.
Significance The use of light-emitting electronic devices for reading, communication, and entertainment has greatly increased recently. We found that the use of these devices before bedtime prolongs the time it takes to fall asleep, delays the circadian clock, suppresses levels of the sleep-promoting hormone melatonin, reduces the amount and delays the timing of REM sleep, and reduces alertness the following morning. Use of light-emitting devices immediately before bedtime also increases alertness at that time, which may lead users to delay bedtime at home. Overall, we found that the use of portable light-emitting devices immediately before bedtime has biological effects that may perpetuate sleep deficiency and disrupt circadian rhythms, both of which can have adverse impacts on performance, health, and safety.
It is not—unless it triggers feelings of envy. This study uses the framework of social rank theory of depression and conceptualizes Facebook envy as a possible link between Facebook surveillance use and depression among college students. Using a survey of 736 college students, we found that the effect of surveillance use of Facebook on depression is mediated by Facebook envy. However, when Facebook envy is controlled for, Facebook use actually lessens depression.