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S T U D Y P R O T O C O L Open Access
Short-term efficacy of reducing screen
media use on physical activity, sleep, and
physiological stress in families with children
aged 4–14: study protocol for the SCREENS
randomized controlled trial
Martin Gillies Banke Rasmussen
1*
, Jesper Pedersen
1
, Line Grønholt Olesen
1
, Søren Brage
1,2
, Heidi Klakk
1,3
,
Peter Lund Kristensen
1
, Jan Christian Brønd
1
and Anders Grøntved
1*
Abstract
Background: During the recent decade presence of digital media, especially handheld devices, in everyday life, has
been increasing. Survey data suggests that children and adults spend much of their leisure on screen media,
including use of social media and video services. Despite much public debate on possible harmful effects of such
behavioral shifts, evidence from rigorously conducted randomized controlled trials in free-living settings, investigating
the efficacy of reducing screen media use on physical activity, sleep, and physiological stress, is still lacking. Therefore, a
family and home-based randomized controlled trial –the SCREENS trial –is being conducted. Here we describe in
detail the rationale and protocol of this study.
Methods: The SCREENS pilot trial was conducted during the fall of 2018 and spring of 2019. Based on experiences
from the pilot study, we developed a protocol for a parallel group randomized controlled trial. The trial is being
conducted from May 2019 to ultimo 2020 in 95 families with children 4–14 years recruited from a population-based
survey. As part of the intervention family members must handover most portable devices for a 2-week time frame, in
exchange for classic mobile phones (not smartphones). Also, entertainment-based screen media use during leisure
must be limited to no more than 3 hours/week/person. At baseline and follow-up, 7-day 24-h physical activity will be
assessed using two triaxial accelerometers; one at the right hip and one the middle of the right thigh. Sleep duration
will be assessed using a single channel EEG-based sleep monitor system. Also, to assess physiological stress (only
assessed in adults), parameters of 24-h heart rate variability, the cortisol awakening response and diurnal cortisol slope
will be quantified using data sampled over three consecutive days. During the study we will objectively monitor the
families’screen media use via different software and hardware monitoring systems.
(Continued on next page)
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data made available in this article, unless otherwise stated in a credit line to the data.
* Correspondence: mgrasmussen@health.sdu.dk;agroentved@health.sdu.dk
1
Department of Sports Science and Clinical Biomechanics, Research Unit for
Exercise Epidemiology, Centre of Research in Childhood Health, University of
Southern Denmark, 5230 Odense, Denmark
Full list of author information is available at the end of the article
Rasmussen et al. BMC Public Health (2020) 20:380
https://doi.org/10.1186/s12889-020-8458-6
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(Continued from previous page)
Discussion: Using a rigorous study design with state-of-the-art methodology to assess outcomes and intervention
compliance, analyses of data from the SCREENS trial will help answer important causal questions of leisure screen
media habits and its short-term influence on physical activity, sleep, and other health related outcomes among
children and adults.
Trial registration: NCT04098913 at https://clinicaltrials.gov [20-09-2019, retrospectively registered].
Keywords: Screen time, Physical activity, Sleep, Stress, Randomized controlled trial
Background
Time spent using screen-based media devices is ubi-
quitous in everyday life of children and adults of the
twenty-first century. Rapid technological development
and market introduction of handheld screen-based de-
vices, such as smartphones and tablets, to consumers
all over the world, has changed the way and the
amount of time humans interact with electronic
media. To the extent that self-report depicts screen
time habits accurately, evidence suggests that British
children and youth (8–18 years) engage in four hours
and 45 min of screen time a day on average, as a
main activity or while engaging in other activities [1].
Furthermore, results from the same study indicate a
pronounced increase in screen time from 2010 to
2015 in British children [1] and an increase in com-
puter use during leisure hours from 2001 to 2016 in
mostagegroupsinNorthAmerica[2] has been re-
ported. Based on a 2018 survey of 3660 school chil-
dren in Denmark, 24% of boys and at least 19% of
girls aged 13 and 15 spend at least four hours/day on
weekdays watching movies, tv-series, Youtube-movies
or entertainment shows [3]. Also, 88% of adult Danes
report using the internet daily, as part of their daily
routine [4]. Clearly, adults and children spend much
of their leisure time engaging in some form of
entertainment-based screen media.
In the public debate, there is much discussion about
whether use of screen media carries a risk to our mental
well-being and physical health. According to a 2016
Technical report from The American Academy Pediatrics,
screen-based media use includes some beneficial effects,
such as improved knowledge acquisition at an early age,
access to important information and creating enhanced
opportunities for communication [5]. However, there is
also evidence which suggest that screen media use has a
negative relationship with children and adolescents’sleep
[6], as well a myriad of other aspects of health, including
adiposity, unhealthy dietary pattern, symptoms of depres-
sion, a poor quality of life [7] and decreased physical
activity [8]. Of concern may be the effect of excessive
screen time in childhood on children’s physical activity
habits. Some evidence suggests that childhood physical ac-
tivity habits track to some degree into young adulthood
[9] and concerns may therefore be raised regarding
lifelong physical inactivity.
Sincejustbeforetheturnofthecentury,experi-
mental studies have been conducted to investigate the
effect of change in screen media use on health-related
outcomes in children. Among the randomized con-
trolled studies, which have investigated the effect of a
reduction in screen media use on physical activity
[10–17], only one found significant increase [14].
However, this trial was limited by measuring physical
activity by self-report [14]. This and several of the
other randomized controlled studies are limited by
small samples sizes [10,11,13,14] and only one trial
measured change in screen time via an objective in-
strument [15]. Furthermore, only one study empha-
sized the impact of a screen media reduction on
change in physical activity in adults (the primary
caregiver) [12].
In addition to the effect of screen time on physical ac-
tivity, some recent lab-based experimental evidence sug-
gests that exposure to digital screens may also negatively
affect circadian rhythm and sleep in adults [18–20]. Al-
though some evidence suggests an impact of limiting
screen-based media use on health, several of the studies
include noteworthy methodological limitations. There-
fore, we are still limited in our basic understanding of
the causal relation between screen media use and phys-
ical activity, sleep and physiological stress. Furthermore,
because of staggering screen media technology changes
in the past decade, some existing research on screen
media use may have limited generalizability to current
screen time behavior and culture. Rigorously conducted
randomized controlled trials in free-living settings in-
cluding adults and children, employing objective mea-
sures to detect changes in both exposure and outcomes,
are needed to refute or confirm hypotheses of how ha-
bitual use of screen media, in its modern form, affects
physical activity, sleep and physiological stress. The
SCREENS trial is a randomized controlled trial which
aims to investigate the short-term efficacy of limiting
leisure screen media use on objectively assessed habitual
physical activity, sleep duration and quality, in parents
and their 4–14-year old children and measures of
physiological stress, in adults.
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Objectives
The objectives of the SCREENS trial are to investigate
the short-term efficacy of limiting screen media use dur-
ing leisure on adults’and children’s:
–Non-sedentary time (all activities not performed in a
sitting or lying position) during leisure measured by
combined hip- and thigh worn accelerometry
–Total sleep time, sleep latency, and wake after sleep
onset measured by home-based single channel elec-
troencephalography (EEG) sleep monitoring
–Parent reported psychological well-being, in their
children
–Leisure- and total time engaged with moderate- and
vigorous physical activity
Also, in adults, the objectives of the study are to inves-
tigate the short-term efficacy of limiting screen media
use during leisure on:
–Subjectively assessed sleep quality
–The cortisol awakening response and diurnal cortisol
obtained from saliva sampling, as markers of
physiological stress
–Heart rate variability using 24-h assessment, also as
a marker of physiological stress
–Self-reported mental well-being and mood states
The study tests the hypotheses that restricting leisure
screen media use to an amount much below habitual
levels for a period of two weeks increases leisure time
spent being non-sedentary, increases total sleep duration
and decreases markers of physiological stress, in families
of adults and children.
Methods/design
SCREENS pilot trial
From November of 2018 to March of 2019 we conducted
the SCREENS (not an abbreviation) pilot trial (Clinical-
Trials.cov ID: NCT03788525) in families residing in the
Municipality of Middelfart on the Island of Funen, in
Denmark. The purpose of the pilot was to assess degree of
compliance to the prescribed intervention, compliance to
home-based objective assessments of physical activity,
sleep, and measures of physiological stress. The purpose
was furthermore to assess feasibility of our recruitment
strategy, as well as resources required of participants and
researchers involved and other general aspects of conduct-
ing such a study, previously outlined in detail [21]. Prelim-
inary results from the pilot study show that the
measurement and intervention protocol generally were
feasible, although adjustments prior to conducting the
full-scale randomized controlled trial of the SCREENS
trial, were necessary. These adjustments are included in
the protocol for the full-scale SCREENS randomized con-
trolled trial described in this paper.
SCREENS survey and randomized controlled trial
This study was commenced when a survey was sent out
medio May 2019 to selected postal districts in the Muni-
cipality of Odense. The study is now being expanded to
the remaining municipalities on Funen (except Middel-
fart). The following sections will describe in detail the
methodology of the SCREENS trial, including a descrip-
tion of the recruitment processes based on a population-
based survey. A home- and family-based screen media
use reduction intervention will be evaluated using a two-
arm, parallel, randomized controlled superiority trial de-
sign. This study protocol was developed in accordance
with the SPIRIT 2013 checklist for study protocols of
randomized controlled trials (see Additional file 1).
Recruitment process
The recruitment consists of two stages; the first stage is
sending out a survey to approximately 3000 Danish
adults residing in the municipality of Odense (the fourth
largest Danish municipality) or neighboring municipal-
ities, via an electronic mailbox system (e-boks) available
to Danish citizens. There is a dual purpose of the survey;
first, to obtain extensive descriptive data on modern
screen media behavior among adults and children 6–10
years of age, and secondly, to serve as a recruitment
platform for the SCREENS trial. Survey respondents will
at the end of the survey be invited to hear more about
the SCREENS trial. The second stage include contacting
families who have responded to this invitation. Stage 1
and stage 2 will be repeated, in the different municipal-
ities. Adults whose families are eligible are invited to
participate in the trial. A broad overview of the survey
send outs and recruitment for and participation in the
SCREENS trial is given in Fig. 1.
Stage 1: Recruitment via survey
Figure 2gives an overview of the flow of participants
through the study in its entirety. For the survey, one ran-
domly selected adult and one randomly selected child
household member between six and ten years of age will
be invited. To receive the survey, the adult and the child
must share an address and the adult must have full cus-
tody of the child, according to the Danish National Civil
Registry. No further restrictions are put on the invitees
of the survey and thus all households in the municipal-
ities that meet the criteria above will be invited. The
sampling frame of the survey invitees was gathered from
the Danish National Civil Registry obtained through the
National Health Data Authority. The survey includes
questions for the adult pertaining to the adult’s and the
child’s screen media habits, including amount of screen
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use and questions on other domains of the family screen
media home environment, such as rule setting.
Respondents are asked in the survey whether they
would like to be contacted regarding a different study
(the SCREENS trial). Therefore, all potential participants
of the SCREENS trial will be survey respondents. Those
who answer ‘yes’to the question in the survey and who
meet the following preliminary inclusion criteria (based
on survey questions) will be contacted via phone regard-
ing participation:
–The adult must be classified as having high screen
media use, which we define as being above the 40th
percentile for total screen time during leisure,
according to a questionnaire battery, included in the
survey. The 40th percentile was estimated as 2 h and
~ 23 min/day (weighed average of week- and weekend
days) based on the first 1000 survey respondents (all
from the Municipality of Odense). This arbitrary cut-
point was defined as a compromise between assuring
enough eligible adults such that recruitment into the
study would progress at a reasonable pace, whole mak-
ing sure to include only those with enough screen
media use during leisure. This criterion was based only
on the adult who completed the survey, as arguably his
or her screen media use to some extent could be a
proxy for the screen media use of the entire family.
–To exclude families who are coping with e.g. disturbed
sleep patterns and others stress factors from having
either newborns, toddlers or very young children,
households must include only children ≥4 years of age.
–Adults must not be outside the labor market or
educational system.
–Adults must not have any regular night shifts.
Recruitment via surveys will continue until we reach
the number of participants required for the statistical
analyses (see “Justification for sample size”). We expect
Fig. 1 Overview of surveys and subsequent recruitment for and conduct of the SCREENS trial. A visual overview of the approximately one-and-a-
half-year span of the study, which includes digitally mailing out surveys including questions regarding screen media use in children and adults.
Following each survey is recruitment for and conduct of the SCREENS trial. The designation of each month on the x-axis denotes the first day of
said month. Notice that the duration and timing of each wave (survey and experiment) varies, as some of the depicted waves include periods
without any activity because they span holidays. However, for the sake of simplicity, this has not been changed
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to have sampled enough participants for the trial follow-
ing the 8th or second last survey. Thus, in the final sur-
vey, we expect to not include the question regarding the
SCREENS trial (see Fig. 1, to the right).
Stage 2: Recruitment following survey
Those respondents who meet the initial criteria will re-
ceive a phone call from a member of the research team
who will explain the content of the SCREENS trial. Fur-
ther screening will take place in two steps; first, on the
phone, we will screen for health-related matters and
practical issues regarding the project. The adult must
confirm that:
–At least one adult and one child, from the
household, is willing to participate
Fig. 2 Flow chart of participants from recruitment to statistical analyses. The flow chart above gives a broad overview of the recruitment
processes via an electronic survey, initial phone contact, meeting in the families’household, participation in the SCREENS trial and, ultimately, the
statistical analyses. R; Randomization, *; Possible source of missing data, **; Stages at which participants may choose to discontinue
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–The family has the resources, primarily in terms of
spare time, to complete the study as outlined. This
includes being able to restrict leisure screen time,
including in weekends, during a two-week
timeframe
–At least one participating adult and all participating
children must be able to hand-over their smart-
phone(s) and tablets for the screen time restriction
period
–The family is motivated to restrict leisure screen
time for a short period of time
These exclusion criteria for both adults and children
include:
–Not being able to engage in regular physical activity
during everyday life
–Having a diagnosed sleep disorder that continues to
affect sleep
–Diagnosed with or in the process of being cleared
from any neuropsychiatric disorders, such as
attention deficit hyperactivity disorder, or
developmental disorders, such as autism spectrum
disorders
–Been on sick leave within the last 3 months due to
stress
If families are eligible according to the criteria above, a
mandatory information meeting of approximately 45
min will be held at the family’s home. Here, the study
will be explained in detail, also including a demonstra-
tion of the measurement equipment used in the study.
At this meeting we will also register the amount of
screen media units available in the household. All fam-
ilies will be offered a minimum of 24 h to consider
whether they would like to participate. Families are
handed a written consent form, which must be filled
out, before participation in SCREENS trial. Figure 2
below provides a complete overview of the flow of par-
ticipants through the study in its entirety.
‘Active’and ‘passive’participants
Based on our experience from the SCREENS pilot trial,
some families choose or are only able to include some
family members in the study. Those who participate we
define as ‘active’participants. Conversely, members of
the household who do not take part in the study are
defined as ‘passive’participants. If a family chooses to in-
clude only partial participation of the household, it is an
inclusion criterion that ‘passive’participants fully sup-
port the constraints of the 2-week screen time restric-
tion period that ‘active’participants in the household
must comply with. Teenagers between 15 and 17 years
are by default assigned to be ‘passive’participants.
‘Passive’participants are not required to hand-over their
smartphone(s) and tablet(s).
Participant safety
As the authors are not aware of any side-effects associ-
ated with participation in the study, the study partici-
pants are informed verbally and in writing that they
should notify the researchers if they experience any side-
effects or harm during the SCREENS trial. No specific
protocol to mitigate adverse events has been developed
and there has not been formulated a formal trial termin-
ation procedure. All study participants are informed ver-
bally and in writing that they can withdraw their
participation from the study at any time, without any
need to justify their reason for doing so.
Justification of sample size
The primary outcome is average change in accelerometry-
derived non-sedentary time (min/day) during leisure, in
children. Based on families, who currently either have or
are registered for the SCREENS trial, we expect to include
1.96 children per family. Based on preliminary data from
our pilot, we expect a standard deviation of 57 min/week
for average change in non-sedentary time from baseline to
follow-up in the experimental group and 39.7 min/week
for the control group. Based on other internal work in
children 0–17 years of age, we expect a 0.3 correlation be-
tween sibling non-sedentary time. In regard to clinical
relevancy, a cross-over study found that intermittent inter-
ruptions of walking, amounting to a total of 18 min during
3 hours of sitting, resulted in favorable metabolic changes,
when compared to sitting only, in children 10.2 (1.5) years
of age [22]. For the current study, a 24-min change is
deemed a clinically relevant effect size, based on the ex-
pected between-group difference and project resources.
Therefore, assuming an intraclass correlation coefficient
of 0.3 for sibling non-sedentary time and a cluster size of
1.96 children per family, to detect a 24 min/day difference
with a power of 80% and α= 0.05, a total of 88 families in-
cluding 174 children is required for the analyses.
Thus far we have experienced a 0 % drop-out. There-
fore, the main threat against achieving enough subjects
for our analyses may arguably be missing data. There-
fore, by sampling 95 families into the study, including a
total of 186 children, we have safeguarded our primary
analysis against a family dropout rate or data loss for
other reasons of approximately 7.4%.
Organization of the SCREENS trial
The study is organized into a planning/working group and
a data collection group. The former consists of the entire
list of authors, whereas the latter consists of MGR, JP, as
well as pre-graduate student SS, and student helpers Stud.
Cand. Scient. SM and Stud. Cand. Scient JH.
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Study design and structure of the SCREENS trial
Figure 3gives an overview of the course of the SCREENS
trial, as well as the exposure and outcome measurements.
As illustrated, the SCREENS trial includes three meetings
and one phone call, which takes place in the following
chronological order; a baseline meeting, a post-baseline/
pre-experiment meeting, a mid-experiment/pre-follow-up
phone call and a post experiment/post-follow-up meeting.
The meetings will all take place in the families' household
and will be held by the same member of the research staff.
The baseline and follow-up periods last a week (7× 24
hours) and span 8 days. If e.g. a period starts at 5 pm on a
Wednesday, the period finishes on the same day and at
the same time, exactly a week later.
Intervention
The intervention takes place in the families’household
during everyday activities. The intervention requires that
the family make several changes during everyday life, re-
garding screen time habits, during leisure, for 2 weeks.
Two weeks was chosen as a compromise between assuring
that there was enough time to detect change (including
time to adapt), with how long we could expect families to
heavily restrict leisure screen time. One of the main com-
ponents of the intervention is that portable screen-based
devices (smartphones and tablets) must be handed over to
the research staff for the duration of the intervention. The
devices will be stored in a locked safe at the Department
of Sports Science and Clinical Biomechanics at the Uni-
versity of Southern Denmark. Every family member who
owns a device with a sim card will be offered a Nokia 130
phone in exchange, in which their sim card will be
inserted. The Nokia phone can perform the few opera-
tions that arguably are essential during everyday life; call-
ing, text messaging, and setting alarm clocks.
During the screen media reduction period, which only
targets leisure hours, a finite amount of entertainment-
based screen media use is allowed. Entertainment-based
screen time is defined as; watching streaming-based ser-
vices (Netflix, HBO, Amazon, Youtube etc.), most
Fig. 3 An overview of the SCREENS trial as well as the included measurements. The figure illustrates the course of the SCREENS trial scaled in
days, including the experiment phase and the timing and duration of each outcome measurement protocol. Notice that the protocol for baseline
measurements and the protocol for follow-up measurements, differ only in that there is one additional day of sleep measurement at baseline (a
“test”night to get acquainted with this protocol) and that the questionnaires are administrated at opposite extremes. The first meeting is an
information meeting in the families’household, whereas the second through fourth meeting take place during the trial
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broadcast television, surfing online, gaming, use of social
media to connect with friends and family and more. In
the context of this study, it also includes watching the
news (although it may be debatable whether this is con-
sidered entertainment-based). During the 2-week screen
time restriction, adults and children are allowed up to 3
hours per week per person of entertainment-based
screen media use. On the contrary, necessary screen time
includes brief contact via phone to plan social gather-
ings, including social arrangements with one’s family or
play dates for one’s children, as well as necessary shop-
ping online, e.g. grocery shopping. Necessary screen time
also includes all screen time relating to one’s children’s
school or nursery, e.g. reading information letters from
the teacher. Adults are permitted up to 30 min of neces-
sary screen time per day. Children or adolescents, who
are required to do homework on digital screens, are per-
mitted to do so with no constrains on time. All
entertainment-based and necessary screen time must be
noted in sheets that will be handed out at the post-
baseline/pre-experiment meeting.
The research staff will place three to five ‘interven-
tion reminders’in the household. An ‘intervention re-
minder’is a A5 sheet on which the rules of the
intervention are listed. These will act as environmen-
tal cues, where the goal is that when family members
see the reminder they are reminded of the details re-
garding their participation in the study. The re-
minders will be placed strategically in the household,
including in the living room by the television, at
household computers and in a place where the family
often gathers, e.g. in the kitchen. Table 1.givesa
summary of the core components of the screen media
restriction protocol.
The goal is to intervene as little as possible in the po-
tential behavior change of the family, beyond establish-
ing the framework of the intervention. The purpose of
this is to increase as much as possible the ecological val-
idity of the data.
The control group will continue with their everyday
habits, only interrupted by follow-up measurements.
Those who are randomized to the control group will be
offered to complete the intervention protocol when they
have finished the control group period, although they
will not repeat the outcome assessments a third time.
Scheduling meetings
All meetings and phone calls will be scheduled in ad-
vance of the study. This is to ensure that meetings and
measurements are structured in accordance to the over-
all protocol. This includes making sure that baseline and
follow-up periods are placed at approximately the same
days during the week (to ensure comparability). Lastly,
early planning is also to ensure that the 2-week screen
time restriction is placed at a time where the family can
manage to implement the behavior change. Ideally, the
course of the trial should be scheduled in a manner,
such that baseline and the experiment phase, including
follow-up measurements, are placed back to back. How-
ever, for the latter point, for practical reasons regarding
the family’s schedule, it may be necessary to allow a
week or more to pass between end of baseline and the
beginning of the experiment. Reasons for doing so could
be that a family is travelling at this time or if there are
Table 1 Summary of core components of the screen media reduction protocol
Core components Content
Planning the course of the SCREENS trial Careful scheduling of the trial between researcher and family, such that the
2-week restriction in screen time is possible
Installation of screen time monitors on household devices Installation of software or hardware on the screen-based devices in the household,
including televisions, computers and portable devices (smartphones and tablets)
Encouraging the family to plan for 2-week screen time break The family will fill out a form where they note potential challenges and solutions
to challenges during a 2-week screen time break
Handing over portable screen-based media devices At least one participating adult and all participating children must hand over
their portable screen-based devices (smartphones and tablets)
Restrictions on leisure entertainment-based screen time Family members must limit their entertainment-based screen time during
leisure hours to ≤3 h/week/person
Allowing for some necessary screen time Adults are allowed no more than 30 min per day of necessary screen time,
during leisure hours.
To the extent that it is necessary, young adults can do their homework
with no limit in terms of time. All necessary screen time must be noted.
Registration of all screen time during experiment phase The family members must register all screen time, entertainment-based
and necessary, during the experiment phase, on paper sheets
Placing three to five ‘intervention reminders’in household One in living room on television(s), one at a computer and one in a place
where the family often gathers
Financial incentive upon completion of the study Each family receives 500 DKK upon completion of the study
The table above gives an overview of the core components of the SCREENS trial and includes a short description of what these each entail
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upcoming television events, which the family would like
watch, e.g. national soccer events, which collide with an
experiment phase scheduled at an ideal time. Judge-
ments regarding scheduling conflicts will be considered
weighing the importance of assuring progress of the trial
against pragmatic considerations.
Baseline meeting
At the baseline meeting, the research staff will instruct
the families on how to conduct the protocol for collect-
ing data. Because the families oversee data collection
themselves, extensive training will be given regarding the
protocols. At this meeting, the family members will be
instructed start wearing accelerometer belts and we will
also demonstrate the use of the sleep equipment (details
on outcome measurement protocols later).
At the meeting we will install instruments to ob-
jectively assess screen time on the devices in the
household in attempt to accurately monitor compli-
ance. We will install an application (SDU Device
Tracker) on the family members’smartphones, and
tablets. Furthermore, we will mount tv-monitors on
every TV in the household. Finally, tracking software
for PCs will be installed on every PC in the house-
hold, if possible (the monitoring systems are de-
scribed in more detail, later).
At the end of the meeting a sheet will be handed out,
which outlines some of the practical matters regarding
the intervention. The sheet also includes several points
for discussion in the family, as they are encouraged to
discuss what challenges a 2-week screen media use re-
duction period could entail. They are also encouraged to
discuss how any issues might be resolved. This includes
a discussion of how to manage everyday tasks without a
smartphone at one’s disposal. The family members are
encouraged to write down these challenges and their po-
tential solutions.
Post-baseline/pre-experiment meeting and randomization
At the post-baseline/pre-experiment meeting the family
will be randomized by research staff using the Odense
Patient data Explorative Network (OPEN) Randomize
platform (part of a research infrastructure service for re-
searchers in the Region of Southern Denmark), to either
the screen media restriction protocol or to control. Staff
at the OPEN Randomize platform - whom the research
staff do not work with - have generated a randomization
table with a hidden allocation sequence using computer
generated random permuted blocks of 2–4 families and
an allocation ratio of 1:1. After randomization the group
allocation will not be masked to the research staff and
given the nature of the intervention cannot be concealed
from the participants.
At this meeting, we will also handover new accelerom-
eters belts for the follow-up measurements. All other
equipment can be re-used.
Mid-experiment/pre-follow-up phone call
Between the post-baseline/pre-experiment meeting and
the post experiment/post-follow-up meeting, the re-
search staff will phone the contact person in the family.
The purpose of this phone call is twofold; first, to motiv-
ate the family to maintain the screen time reduction
during the entire 2-week duration. The researcher will
ask the family how well they are doing in terms of
restricting their screen time according to the protocol.
Secondly, the purpose of the phone call is to remind the
family that they must soon start up the follow-up mea-
surements and to ask the family if they have any ques-
tions relating to the measurement protocol. The control
group will also receive a phone call, only for the second
purpose.
Post experiment/post-follow-up meeting
At the post experiment/post-follow-up meeting, which
takes place immediately or shortly after the end of the
experiment phase, the researcher will congratulate the
family on their completion of the study. The children
will each receive a colorful diploma signed by the mem-
ber of the research staff in charge of this family. The
families will receive a 500 DKK reimbursement for the
time they put into completing the study (independent of
group allocation).
Theoretical underpinning of intervention
Bandura’s social cognitive theory [23] serves as the the-
oretical framework of the intervention. The reciprocally
determined and causal relationship between an individ-
ual’s environment, his or her personal factors and behav-
ior, as proposed by Albert Bandura [23], serves as a
theoretical underpinning of the core components out-
lined earlier. Specifically, we target personal factors and
induce specific changes to the household environment,
to encourage the families to change, i.e. decrease the
level of their screen time. Conversely, we expect that
changes in screen media use may also influence personal
factors, such as an individual’s biology, as defined by
Bandura [23], e.g. sleep quality, mood, and mental stress.
We specifically target the families at the personal level
through several means. At an early stage in the trial, we
ask the families to discuss and find solutions to issues they
may meet during a 2-week screen media use reduction.
Although the researchers do not get involved in the de-
tails, we encourage planning and goal-setting [24]. The
study is emphasized as family-based and therefore we en-
courage a change in the overall household culture relating
to screen media use. We suggest that parents act as
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models of this new behavior, which might make it easier
for the children to adopt the behavior, as well [25].
Meeting only one research staff member might in-
crease the level of commitment to the intervention
protocol, via increased self-regulation [26] in terms of
decreasing screen media use. This may arguably be be-
cause one knows one must face the same member of the
research team several times during a short time period.
During the 2-week restriction period we make specific
changes to the household environment; we install moni-
toring systems on the household televisions and com-
puters, as well as on smartphones and tablets. We also
place three ‘intervention reminders’,i.e.environmental
cues. The goal of all these environmental changes is to
emphasize self-regulatory processes [26]necessaryto
change and maintain the screen-time reduction. The mid-
experiment phone call is included for a similar purpose.
The goal of the reimbursement following completion
of the study is to have an incentive structure, an extrin-
sic reward, i.e. an reward coming from something exter-
ior to the person [27]. By anticipating a reward, this may
facilitate the self-regulatory processes [26] required to be
compliant to the SCREENS trial protocols.
Below is a table summarizing the elements of Social
Cognitive Theory discussed above (see Table 2). The
table is structured with inspiration from Table 1in the
study by Hinkley et al. [13] aiming to reduce screen
media use in 2–3-year-old children.
Exposure and outcome measurement protocol
As already mentioned, figure three gives an overview of
the overall trial protocol, including an overview of the
timing of measurements. On the first day of baseline
measurement, questionnaires will be administered to the
participants. The questionnaires will be sent by e-mail to
an adult in the household. Then, on the first night, the
first of four sleep measurements during baseline will be
carried out. The first sleep measurement is meant as a
“test”measurement (not included in statistical analyses
and not included at follow-up), as some adjustment to
the sleep measurement protocol is necessary. The three
remaining consecutive sleep measurements will take
place from the night of day five till day six through the
night of day seven till day eight. On day one, accelerom-
eters will be mounted onto the participants and worn
throughout the given measurement period. On day four,
adult participants will be instructed to mount heart rate
variability monitors to their upper body at the same time
accelerometers were mounted 4 days prior. These moni-
tors will be worn for three consecutive days. Therefore,
accelerometry and heart rate variability measurements
will finish on the exact same time on day eight. Finally,
from the morning of day five till the evening of day
seven, adult participants will collect four saliva samples
per day; three in the morning upon awakening and one
before bedtime.
Primary and secondary outcomes and endpoints
The primary outcome is the mean between-group differ-
ence in accelerometry-derived non-sedentary time (min/
day) during leisure, in children. The primary endpoint is
the primary outcome at follow-up assessment (only one
follow-up).
The full list of secondary and exploratory outcomes
can be found at: https://clinicaltrials.gov/ct2/show/
NCT04098913.
Accelerometry
Both adults and children will undergo 24-h accelerome-
try for seven consecutive days using two Axivity AX3
(Axivity Ltd., Newcastle upon Tyne, United Kingdom)
triaxial accelerometers. The sensors are small (dimen-
sions: 23 mm × 32.5 mm × 7.6 mm) weighing only 11 g.
Acceleration is measured in three axes. Sensitivity will
be set to +/−8 g and sampling frequency to 50 Hz.
The accelerometers are worn at two anatomical loca-
tions; one is fixated to the body in a pocket attached to
a belt worn around the waist, where the sensor is placed
Table 2 Bandura’s Social Cognitive Theory (SCT) as a theoretical framework for the intervention
Screen media restriction components SCT level targeted Behavior element targeted
Planning the course of the screen time restriction period.
Hanging notes where family members can see them.
Personal / environment Goal setting, self-regulation
Meeting the same individual from the research team during
several meetings throughout the SCREENS trial
Personal Self-regulation
Emphasizing the project as a family project, including parents as role models Personal and environment Modelling
Installation of screen time monitors on household devices Environment Self-regulation
Placing three to five ‘intervention reminders’in the household Environment Self-regulation
Motivation and encouragement midway through the two-week screen time restriction Personal Self-regulation
Financial incentive upon completion of study Personal Extrinsic reward, self-regulation
The table above gives an overview of the how the components of the screen media restriction part of the SCREENS trial are theoretically grounded in Social
Cognitive Theory. We outline which level that is targeted and which specific behavioral theory which is targeted at this level
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such that it is on the right hip facing away from the right
of the body. A second belt is worn around the right
thigh midway between the hip and the knee, where an
accelerometer is placed in a pocket on this belt facing
away from the body. The devices will be worn for 1 week
(seven consecutive days) at baseline and at follow-up,
which has been suggested as the number of days re-
quired to estimate habitual physical activity [28].
Time spent in distinct activity types (sitting, moving,
standing, biking, stair climbing, running, walking, and
lying down) are determined from the acceleration mea-
sured with the thigh worn device using the method pro-
posed by Skotte et al. (2014) [29] using 1-s epochs. In
this study, the method was validated with adults in a
standardized field test and demonstrated a sensitivity
> 95% and specificity > 99% for all activities. Also,
during almost 6 days of measurement in free-living,
sensitivity and specificity were 98 and 93%, respect-
ively, for classification of sitting time [29]. Children
and adolescent specific decision thresholds for the
method were developed using an internally conducted
study (publication in preparation). The results indi-
cate high sensitivity and specificity of measurement.
Non-sedentary time is defined based on this method
and includes all activities, including standing, other
than sitting and lying. We will analyze non-sedentary
time as the amount per day (total amount per 7 days
divided by seven). In addition, time spent within
physical activity intensity domains (sedentary, light,
moderate and vigorous) will be estimated using Acti-
Graph counts generated with the waist worn device
[30] using 10-s epochs. The cut-points defining inten-
sity domains are determined using an internal calibra-
tion study conducted in a group of children and
adults (results not published).
Non-wear periods are identified and marked as missing
data by evaluating three signal features generated from ac-
celeration in combination with temperature and prede-
fined expected awake time (06:00 AM to 10:00 PM).
Periods of no movement (acceleration below 20 mg) lon-
ger than 120 min are always identified as non-wear and
shorter periods from 45 to 120 min are identified as non-
wear if the average temperature is below an individually
estimated non-moving temperature (NMT) threshold. Pe-
riods of 10 to 45 min with no movement are only identi-
fied as non-wear if the average temperature is below the
NMT threshold and if the end of the period is within the
expected awake time. Device transportation (periods of
device movement when the device is not worn by the sub-
ject) is identified as non-wear if the average temperature
of the period is below the NMT threshold.
A valid day (restricted to leisure time during wake
hours) of measurement will be defined as a day contain-
ing no more than a total of 10 % non-wear. A valid
baseline and follow-up measurement must include at
least three valid weekdays and at least one valid weekend
day. We will include a sensitivity analysis of the valid
data where we impute for each individual non-wear time
based on available data, for the same type of day and
timing of non-wear (time of day).
The software OmGUI version 1.0.0.37 will be used in
the set-up, download, re-sampling and conversion of the
accelerometer data. The raw accelerometry data will be
processed using Matlab (Mathworks Inc., Natick, Massa-
chusetts, US) release R2019a version 9.6.0.1099231.
Sleep monitoring
Both adults and children will undergo sleep assessments
using the Zmachine® Insight+ model DT-200 (General
Sleep Coorporation, Firmware version 5.1.0). The device
measures sleep by single channel electroencephalog-
raphy (EEG) from the differential mastoid (A
1
–A
2
) EEG
location on a 30-s epoch basis. The sleep apparatus is
developed for use in a free-living setting for objective
measurement of sleep, including measurement of sleep
duration and sleep stage classification (Light Sleep (N1
& N2), Deep Sleep (Slow Wave Sleep) and Rapid-eye
movement (REM) Sleep), as well as computation of
sleep-specific quantities, e.g. latency to the respective
sleep stages. The algorithm in Zmachine insight+ has
been compared to polysomnography (PSG) in adults
with and without chronic sleep issues within a labora-
tory setting and shown a high degree of validity for this
purpose [31,32]. The Zmachine device has also been
shown to be valid in terms of classification of sleep; de-
tecting of sleep versus awake with the Zmachine algo-
rithm was done with a sensitivity, specificity, positive
predictive value and negative predictive value of 95.5,
92.5, 98 and 84.2%, respectively against polysomnogra-
phy [31]. A second Zmachine algorithm, which further
differentiates sleep into specific stages, has also been
evaluated; classification of sleep into light, deep and
REM was achieved with sensitivities of 84, 74 and 72%
and with positive predictive values of 85, 78 and 73%, re-
spectively against polysomnography [32].
Three electrodes (Ambu A/S, type: N-00-S/25) are
mounted on the mastoids (signal) and the back of the
neck (ground). Thirty minutes before the subjects plan
to go to bed to sleep, the skin areas are cleansed with an
alcohol swab and then electrodes are attached to the
skin. An EEG-cable connects the three electrodes to the
Zmachine device, whereafter a sensor check is per-
formed to detect whether one or more electrodes are
not mounted correctly. If there are sensor problems,
these are solved swiftly by a simple change of said
electrodes.
Because the Zmachine device has not been developed
for children directly and because some adults may tend
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to twist and turn during sleep, we developed custom-
made pockets, which allow for fixation of the EEG-cable
and Zmachine device itself to the accelerometer belt at
the hip. This fixation assures e.g. that cables will not
wrap around the child’s neck during sleep. We also rec-
ommend these pockets for adults whose sleep includes
much twisting and turning.
Mental stress: heart rate variability, cortisol awakening
response and diurnal cortisol
In adult participants, physiological stress will be assessed
by measuring three components associated with human
stress; the beat-to-beat interval variability (ms) of the heart
[33], the saliva cortisol awakening response (a unique fea-
ture of cortisol circadian rhythm) [34] and 24-h diurnal
saliva cortisol [35]. As habitual excessive screen time may
negatively impact both main stress pathways –the sympa-
thetic adrenal medullary (SAM) axis and the hypothalamic
pituitary adrenal cortex (HPA) axis [36]–we include mul-
tiple measurements of physiological stress.
Heart rate variability
We will collect 24-h measurements of Heart Rate Vari-
ability (HRV) for three consecutive days using the First-
beat Bodyguard 2 HRV measurement device. The device
is non-invasive and allows ambulatory continuous re-
cording of R–R heartbeat intervals in a free-living set-
ting. In addition, after merging and aligning epoch-by-
epoch data on intensity and type of physical activity
from accelerometry with R-R beat intervals, HRV activity
arising from physical exertion will be delineated from
non-physical activity associated HRV activity. The latter
is proposed to be reflective of states of mental stress. A
recent systematic review and meta-analysis provide evi-
dence for construct validity of HRV as an objective
measure to quantify psychological stress [33].
Adults will mount the Firstbeat Bodyguard 2 device to
the chest by electrodes designed for long-term measure-
ments (Ambu A/S, type: L-00-S/25); one electrode will
be attached to the right side of the body, immediately
below to collarbone. The second electrode will be at-
tached to the left side of the body, at the level of the rib
cage. The Firstbeat device will be attached to the elec-
trode below the collarbone and from the device a cable
will connect to the electrode on the rib cage.
Raw R-R heartbeat intervals will be processed using
Kubios HRV Premium 3.0.2. including algorithms for
beat detection and artifact correction for each data file
and subsequent calculation of HRV time-, −frequency
and non-linear domain summary data [37,38].
Salivary cortisol awakening response
A distinct component of diurnal cortisol rhythm in
healthy humans is the morning rise in cortisol, which is
a steep rise in cortisol during the 45 min following awak-
ening. When the pattern of morning cortisol rise devi-
ates from what is normally observed, it is argued that
this is reflective of malfunction in neuroendocrine sys-
tems [39].
As recommended as a minimum for measurement of
the cortisol awakening response, adult participants will
collect saliva samples immediately upon awakening, 30
min and 45 min following awakening [39]. The saliva sam-
ples will be collected using Salivette®, code blue (Sarstedt),
which contains a swab that absorbs saliva during chewing.
Immediately at awakening, the participants will deliver the
first saliva sample. Participants are instructed to not re-
move the electrodes and sleep apparatus (described earl-
ier) until after the first saliva sample has been collected,
such that awakening time can be assessed. Also, at awak-
ening, the participants will start a dual timer (S. Brannan
& Sons Ltd., England), which is set to count down from
30 and 45 min, simultaneously. When the timers reach 0,
a distinct alarm tone rings notifying the participants that
they must collect a second and third saliva sample, re-
spectively. According to expert consensus it is recom-
mended that caffeinated and sugared drinks, as well as
food/breakfast is not consumed over the measurement
period in the morning. Although brushing one’s teeth dur-
ing cortisol saliva sampling is allowed [39], we have
chosen a more conservative approach where we disallow
this 10–15 min before each saliva sample. After each sam-
ple is delivered, the participants must place the sample in
their household freezer.
In a checklist (described later) participants must report
the exact time at which a saliva sample has been deliv-
ered. Also, the participants are handed a series of pairs
of barcoded stickers, which contain a unique identifier
for the person and the sample. After each sample, one
sticker must be put in the personal checklist in a section
indicating which saliva sample has be taken (day and
time), whereas the other is put onto the Salivette con-
taining the sample. In the checklist, also time of saliva
sampling is reported by the subject.
At the final meeting, the samples will be transported
in a freezer box to the Department of Sports Science
and Clinical Biomechanics at the University of Southern
Denmark. Here, they will be stored at −20 degrees Cel-
sius. When enough samples have been transported to
the Department (no more than 500 samples), they will
be transported in a freezer box from the University to
the Clinical Biochemical Department at Slagelse Hospital
(~ 70 km drive) for analysis for cortisol and cortisone
content using the LC-MS method (Phenomenex Inc.,
USA, application 20,655). Before analysis, the samples
are stored in the laboratory freezer at −80 degrees Cel-
cius. The laboratory has external quality control of their
chemical analyses of salivary cortisol and cortisol by UK-
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NEQAS, England and are ranked satisfactory. The re-
search staff will have continued dialogue with biochem-
ists at the laboratory to assure that protocols for correct
storage and analysis are met. Following laboratory ana-
lysis, the samples will be destroyed.
Salivary diurnal cortisol
Diurnal cortisol is composed of multiple measurable compo-
nents of cortisol dynamics; first, as described above is the
cortisol awakening response, and secondly, the decline of
cortisol across the span of the day, i.e. the diurnal cortisol
slope. In line with previous research [35], we will assess diur-
nalcortisolbyaddingasinglesaliva sample immediately be-
fore bedtime beyond the three saliva samples in the
morning hours. By measuring cortisol at four points during
daytime, we will estimate diurnal cortisol levels, to assess the
state of the HPA axis output [35] during the span of the day.
Overview of questionnaires
In addition to the physical measurements we will also
administer questionnaires at baseline and follow-up, to
assess the effect of the screen media use restriction on
different psychological and physical constructs. The
adults will answer the following questionnaires; WHO-5,
Profile of Moods Scale [40] and two components of the
Leeds sleep evaluation questionnaire [41]. On behalf of
the participating children, the adults will answer the
Strength and Difficulties Questionnaire [42].
WHO-5
To assess the adult participants’subjective sense of well-
being we will administer the WHO-5 [43]. The tool con-
sists of five simple and non-intrusive questions regarding
an individual’s psychological well-being. The question-
naire has been translated into more than 30 languages
and has been used in countless studies around the globe.
WHO-5 has been demonstrated to be applicable in a
wide array studies; it has been valuable tool in clinical
studies, as well as a screening tool for depression. The
clinometric validity of WHO-5 has been shown to be
high [43].
Leeds sleep evaluation questionnaire
To assess subjective sense of restlessness during sleep
and degree of interrupted sleep, we will use two of the
10 items of the Leeds Sleep Evaluation Questionnaire.
The questionnaire items are answered on a visual
analogue scale. The tool in its entirety has shown to be
valid in some populations, both in healthy and in dis-
eased individuals [41].
Profile of mood states
The adults’mood state will be assessed using the original
64-item Profile of Moods States questionnaire, which is
comprised of six scales relating to 6 states or emotions.
The questionnaire has been used in psychological research
for decades and has shown high internal consistency and
construct validity for its mood scales [40].
Strengths and difficulties questionnaire
Data on Children’s wellbeing and mental health will be
collected using the Danish parent reported Strength and
Difficulties Questionnaire (SDQ) including the one-
month follow-up versions, covering the age band 2–4,
5–6, 4–10 and 11–17 years adapted to kindergarten or
school conditions. Parent reported SDQ has in general
provided good psychometric properties [44,45], also re-
ported for Danish children [42]. Besides the total SDQ
score and daily function, the broader internalising, exter-
nalising and prosocial subscales [46,47] will be of pri-
mary interest in this low-risk population study.
Objective monitoring of screen time: television,
smartphone, tablet and computer activity
As shown in Fig. 3, throughout the entire course of the
SCREENS trial we will objectively measure screen time
on the participating families’devices, including portable
devices, such as smartphones and tablets, as well as tele-
visions and computers.
SDU device tracker: monitoring of smartphone, tablet and
personal computer activity
We have developed a non-commercial monitoring de-
vice (SDU Device Tracker) for monitoring screen time
activity on smartphones, tablets and personal computers.
For tablets and smartphones, the software is installed as
an application using a custom-made QR-code. The app
can track screen time activity, as well as the amount of
times a device has been picked-up (opened). The app
registers data on a second-to-second basis, thus allowing
for detailed analysis of timing and amount of screen
media use. We have developed a Python-based (Python
3.7.3) data reduction software, which perform data qual-
ity control and can summarize individual app data.
Based on the processing of the data diagnostics of the
application activity can be made, including how many
times the app has been closed (force quitted) by the user
and for how long, thus quantifying the amount of time
where screen media use has not been recorded. Data
from the application is continuously sent encrypted to a
secure server at the University of Southern Denmark.
The application is currently compatible with iOS and
Android systems (smartphones and tablets) and OS X
and Windows (PCs).
Although SDU Device Tracker will be installed on
most devices, it may only be installed on devices where
there is a possibility that said device will be used by a
family member. Families may own several devices,
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including devices that they no longer use, e.g. devices
stored in their basement. Therefore, due to time con-
straints during scheduled meetings, we may not install
SDU Device Tracker on unused devices. However, we
will take a conservative approach and install the applica-
tion on most devices, where there is a small chance that
said device might be used. For devices used for work, we
may not be permitted to install the application.
The SDU Device Tracker applications have undergone
extensive internal validationandqualitycontrolandweare
currently conducting ongoing formal validation of the apps.
TV-monitoring device
A small electronic device was developed by engineers at
our department (Department of Sports Science and
Clinical Biomechanics) to assess the amount of TV
usage. Detecting TV usage is assessed by measuring the
power cord current using a hall sensor. A hall sensor is
a current sensor generating a voltage proportional to the
current flowing through the sensor. The voltage is con-
verted using an analog to digital converter with the in-
stalled micro-controller, in 1-min epocs. TV usage is
detected by using a simple threshold, which is set sub-
stantial higher than the stand-by current (equal to or
above the signal strength half-way between the mini-
mum and maximal). By using this threshold, we also
consider the fact that some TVs exhibit short burst of
electrical activity, often during nocturnal hours. These
signals, which are multiples above standby signal
strength, but also multiples below television activity
(which is often a 5-fold signal stronger than stand-by
mode). The signals are characteristic of TV, which
download information for the TV-users, when the TV is
shut off. By using the defined cut-off above, TV-time is
easily distinguished from these shorts burst of electrical
activity not associated with TV usage.
At baseline, we hand out a television usage checklist,
which we place by each television with more than one
user. Each checklist will contain a page for each day of
the baseline period. Here, each family member must
mark whether they have used the television in 15-min
intervals of the day (03:00–03:00). It is possible for fam-
ily members to mark the same time slots. The marked
time slots will then be cross-referenced with the object-
ive measures of tv-usage to categorize individual TV
usage on shared TVs.
We may refrain from installing a TV-monitor on tele-
visions that may never be used, e.g. TVs tucked away in
the basement, which may not even be plugged in.
Sheets and personalized checklists
Diaries
During the intervention, the subjects must fill out small
sheets. First, every member of the family must report the
amount and type of entertainment-based screen time
that they have used, of the up to three hours per week,
which is permitted. Each family member is handed their
own personal sheet to fill in these details. Secondly, the
subjects are asked to report, on a separate paper, if they
have exceeded the limit for entertainment-based screen
media use. In this sheet, any screen media use of ‘pas-
sive’participants, is also reported. Third, for those par-
ticipants for whom screen time is necessary during
everyday life, i.e. during school- or work life, a third
sheet is handed out. On this sheet this necessary screen
time during the 2-week experiment period must be
noted.
Personalized checklists
Each participant will receive a detailed but concise per-
sonal checklist, which chronicles the content of the base-
line and follow-up days in terms of the respective
measurement protocols. Each checklist contains the
dates and times which are relevant to the physical mea-
surements, including e.g. when devices should be worn,
when existing electrodes must be switched to new ones
and when devices must be removed. As described earl-
ier, adult participants must also register the number and
timing of the saliva samples that they have collected.
Participants must also register any irregularities pertaining
to the physical measurements, e.g. issues with timing and
reasons for non-wear. Lastly, in the checklist participants
must also when they wake up, when they go to work or
school (and if they are sick), when they leave work or
school, as well as when they go to bed. This information
will also be used to time annotate the time series data.
Compliance
To estimate the degree to which families are compliant
to the intervention two calculations will be made for
each family: 1) a calculation of a threshold for compli-
ance for entertainment-based screen time and 2) an esti-
mate of total entertainment-based screen time during
the intervention. The threshold for compliance will
equal the maximum entertainment-based screen time
permitted. The threshold is calculated by multiplying the
number of participating family members by 3 h/week of
permitted screen time and multiplying this by 2 weeks,
i.e. the duration of the experiment.
Threshold for family−wise compliance
¼n participating family members 3 hours=week
2 weeks
In this calculation it is assumed that each family mem-
ber uses their permitted screen time by themselves. As
family members may use their entertainment-based
screen time together, we expect that a compliant family
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will have a level of entertainment-based screen time
lower than the compliance threshold.
To estimate the total amount of entertainment-based
screen time, multiple sources of data will be used. First,
objectively measured TV-, smartphone-, tablet-, ipad-
and PC-time will be summarized. Then, entertainment-
based screen time by self-report, on devices whose activ-
ity we do not measure, e.g. TV-viewing on a TV outside
the household, will be added to the summary of object-
ively assessed data. Next, we will subtract all self-
reported necessary screen time on devices that we meas-
ure, which otherwise would be considered entertainment
based. Lastly, we will subtract all screen time (entertain-
ment-based and necessary) by ‘passive’participants.
Family−wise level of entertainment−based screen time
¼total objectively measured screen time min=2 weeksðÞþself−reported
entertainment−based screen time beyond objective measures min=2 weeksðÞ
self−reported necessary screen time min=2 weeksðÞin objective measures
self−reported screen time in objective measurespassive participants min=2 weeksðÞ
To compute degree of compliance for a family, we will
calculate the proportion of entertainment-based screen
time of the compliance threshold, where a number
below or equal to 1 or 100% will indicate that the family
have been compliant to the intervention protocol.
We will also attempt to calculate individual level
compliance using all the available data sources. How-
ever, this computation may be complicated by the
fact that it may not always be clear who the user of a
shared device is. For this reason, it may be difficult to
parse all screen media use in a household onto dis-
tinct users. Also, although we will attempt to describe
individual usage on shared televisions based on televi-
sion usage checklists filled out during baseline (de-
scribed earlier), we cannot be certain that tv usage
profile during baseline can be generalized to the re-
mainder of the study period.
Questionnaire: feasibility of and compliance to the
intervention
At the end of the intervention, each adult must complete
a questionnaire concerning; 1) the degree to which the
adult was compliant to the intervention protocol, 2) the
challenges and opportunities the family faced during the
2-week screen time reduction period and 3) the changes
that were made during everyday life during the period of
the intervention. Questions relating to the latter will
mainly be concerned with what activities that were in-
troduced or emphasized, when screen time was no lon-
ger possible to the same extent. One of the adults must
also complete a similar questionnaire on behalf of the
children.
Background data
Basic background information is collected in the survey,
including educational attainment according to the Inter-
national Standard Classification of Education, work ex-
perience and current employment, as well as household
constellation. Data on ethnicity (ethnic origin) is gath-
ered from the Danish Civil Registry and is available for
the selected children and selected adults, as well as other
parents of the child not registered at the same address.
From the survey and initial meetings with the families,
data on screen time habits and culture within the family
household regarding screen time is collected. Beyond the
amount and timing of screen time, data on the number
of devices in the household, the age when the child had
his/her own smartphone, rules regarding screen media
use and screen media culture around family meals,
among others, is also collected. At baseline, each adult
on behalf of themselves and their child must report their
current bodyweight (kg) and height (cm) to compute
body mass index. Also, data on gender and age will be
collected for all participants.
Data safety
Survey data will be collected and stored using REDCap (a se-
cure application for building and managing online surveys
and databases), which is managed by the researcher service
organization OPEN in the Region of Southern Denmark.
This mode of storage is in accordance with the General Data
Protection Regulation for data handling. Exposure and out-
come data collected during the trial will be stored in the fam-
ilies’households until completion of the study, after which it
will be transported back to the University of Southern
Denmark. At the University, data will be extracted from the
measurement devices and stored in safe folders on the
University servers.
Currently MGR, JP, LGO, PLK, JCB, AG and our pre-
graduate research scholar and two student helpers have
been granted access to the data by the Danish Data Pro-
tection Agency. The data will be stored in its raw form
and no statistical investigation will be conducted, before
the data collection is complete.
Statistical methods
A detailed description of data management and our a
priori planned statistical analyses can be found at (see
'Study documents'): https://clinicaltrials.gov/ct2/show/
NCT04098913?cond=screens&draw=2&rank=1.
Discussion
This paper describes in detail the protocol for a random-
ized controlled trial that aims to investigate the short-
term efficacy of limiting leisure screen media use on ob-
jectively assessed habitual physical activity, sleep, and
Rasmussen et al. BMC Public Health (2020) 20:380 Page 15 of 18
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
physiological stress in parents and their 4–14-year old
children, in free-living.
The SCREENS trial addresses a research gap and limita-
tions of observational and experimental studies of the ef-
fects of screen media use in children and adults. This
includes possible lack of generalizability of experimental
laboratory findings to free-living conditions, that may limit
findings from acute effect cross-over studies of exposure
to digital screen devices during evening hours and sleep
[18,19,48,49], and of acute effects of availability of screen
devices on physical activity behavior [50]. The study also
attempts to overcome limitations from experimental stud-
ies conducted in free-living that have not documented
compliance to screen media during intervention precisely,
or have not minimized noncompliance [12,14]. In our
study we will attempt to objectively monitor compliance
by installing newly developed monitoring systems on
screen time devices in the participating families’house-
holds. This will markedly decrease the reliance on mem-
ory and influence of social desirability bias in gathering
compliance data on screen media use. Also, we have taken
important steps in the enrollment phase (e.g. exclusion
based on parents’perceived resources for behavior
change) to enhance the families’compliance to the screen
media restriction protocol and during the intervention by
closely following the families and optimizing the partici-
pants’experience. In an efficacy trial conducted in free-
living condition as the present, these aspects are essential
to make valid causal inferences from the data. Also, im-
portantly, much of the available research on screen time
and health is, for obvious historical reasons, not based on
screen media use in its modern form, but rather television
usage, and is also to a large extent based on self-report [7].
Our goal is that results from statistical analyses will
move the field forward towards answering causal ques-
tions which currently remain unanswered. Furthermore,
registration of screen time activity is collected in no
higher than 1-min intervals, and opportunities for inves-
tigating with high accuracy and detail, not only how
amount but also timing of screen time exposure is re-
lated to parameters of health, will be rendered possible
in secondary exploratory analyses. By merging objective
data on screen time consumption, with high-quality 24-
h measurements on highly detailed accelerometry and
heart-rate-variability, as well as detailed EEG data during
nocturnal hours, we will generate a data resource from
which detailed investigations are possible. Also, by con-
ducting the study in a familiar setting, i.e. in the families’
home during everyday life and not in a laboratory, the
ecological validity of the results will be high.
We hope that the findings from this study, will help
advance the research frontier within the field of screen
time and health. Importantly, it is our vision that the re-
sults from the SCREENS trial, alongside results from
other new studies in the field, will provide a solid foun-
dation for policy makers to make political decisions re-
garding usage of screen-based media, e.g. formulate
concrete national guidelines or recommendations for
screen media use in children, adolescents and adults.
Also, as we expect that our findings will be of public
interest, the results will be disseminated to practitioners
in relevant fields, including practitioners in municipal
settings as well as at institutions in the private sector,
whose work revolves around childhood health. Also, re-
sults will be presented at scientific conferences nation-
ally and internationally and published in peer-reviewed
journals (regardless of the direction of the findings). Our
work may inspire our scientific colleagues in their future
work, including replication of our study in other national
and cultural settings, as well as developing intervention
studies, whose aims are to facilitate long-term behavior
change regarding screen time for specific populations
who consume screen media in excessive amounts.
Supplementary information
Supplementary information accompanies this paper at https://doi.org/10.
1186/s12889-020-8458-6.
Additional file 1. SPIRIT_checklist.doc’. The additional file includes the
SPIRIT checklist for study protocols of clinical trials, regarding the
SCREENS trial. An indication of where we have addressed each item is
noted in the checklist.
Abbreviations
HRV: Heart rate variability; OPEN: Odense patient data explorative network
Acknowledgements
We would like to thank the twelve families who participated in the pilot
study, whose participation helps finalize the development of the SCREENS
trial and thus the protocol included in this paper.
We would also like to thank the researcher service organization OPEN for
their work now and in the future, which includes sending our electronic
survey’s and cover letters, as well as managing the storage of data from the
SCREENS trial under conditions which comply with the General Data
Protection Regulation.
We would also like to thank Henrik Olsen and Kristian Jacobsen of the
engineer staff at the Department of Sports Science and Clinical
Biomechanics, for the many hours they spent creating and testing the tv-
monitors. We also want to thank software engineer Kasper Dissing Bargsteen
for the development and testing of the tracking software for windows and
mac personal computers.
Authors’contributions
Initial development of study and acquisition of funding: AG PLK JBC LGO SB.
Further development of study design and methods: AG MGR JP LGO PLK HK.
Wrote the first draft for the manuscript: MGR. Contributed to the further
development and writing of the manuscript: All authors. Approved the final
version: All authors. All authors contributed to the current work in a
manner which complies with The International Committee of Medical
Journal Editors [51].
Funding
A European Research Council Starting Grant (no. 716657) was the source of
funding for the project.
The funders had no role in the design of the study design, nor did they play
a role in the collection, management, analysis, and interpretation of the data
from the study. Nor did they have a role in the writing of the study protocol
Rasmussen et al. BMC Public Health (2020) 20:380 Page 16 of 18
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
as well as in the decision to submit the report for publication in BMC Public
Health.
Availability of data and materials
Upon completion of the data collection process and when structured
datasets have been developed, the data may be made available for use
beyond the research staff involved. Availability of the data and the material,
including coding and material, e.g. consent forms and checklist templates,
used in the data collection process, can be made available upon application
to the head of research and project leader of the SCREENS trial Professor
Anders Grøntved (agroentved@health.sdu.dk), as well following upon
approval from the Danish Data Protection Agency, if necessary.
Ethics approval and consent to participate
The SCREENS trial was approved by the Scientific Committee of Southern
Denmark (Project-ID: S-20170213 CSF). For the survey, opening the survey
window includes consent. Furthermore, the survey concerns an adult and a
child, of which the adult has full custody of said child.
Written consent will be gathered before any participation in the SCREENS
randomized trial is possible. Although parents will consent verbally and in
writing on behalf of their children, signs of child dissent will be
contraindicatory to participation in the SCREENS trial. The research staff in
charge of each family will gather the filled-out consent forms.
Any amendments, e.g. changes to inclusion criteria or changes to the
intervention protocol, will be submitted to the Scientific Committee of
Southern Denmark. No such changes will be implemented before written
approval of the amendments has been received by Anders Grøntved (Head
of research). The amendments will also be added to the clinicaltrial.gov
registration and must also be reported to the European Research Council
(major funder).
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Department of Sports Science and Clinical Biomechanics, Research Unit for
Exercise Epidemiology, Centre of Research in Childhood Health, University of
Southern Denmark, 5230 Odense, Denmark.
2
MRC Epidemiology Unit,
Cambridge School of Clinical Medicine, Institute of Metabolic Science,
University of Cambridge, Box 285, Cambridge Biomedical Campus,
Cambridge CB2 0QQ, UK.
3
Department of Physiotherapy and Research
Center for Health Science, University College Lillebælt, Odense, Denmark.
Received: 24 February 2020 Accepted: 4 March 2020
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