The proposed project aims to disentangle the impact of evening light exposure emitted from tablet devices from the impact of arousing media content on children's sleep regulation, circadian physiology and next-day emotion regulation and executive functioning.
Investigators will conduct a 4-group randomized, controlled trial including 200 children (8 to 11 years; Tanner stage 1 or 2) assigned to an unfiltered bright light screen (BL; 109 lux) or a dim light screen (DL; \<5 lux) condition in room lighting (40-50 lux) matched with either calming (CC) or exciting content (EC). Children will participate in two weekend protocols, an experimental and a control weekend. During the experimental weekend, children will be exposed to 1 hour of tablet use in the hour before bed under the following conditions: 1) unfiltered bright screen light and exciting content (BL/EC), 2) unfiltered bright screen light and calming content (BL/CC) 3) filtered dim screen light and exciting content (DL/EC) and 4) filtered dim screen light and calming content (DL/CC). To control for the effect of screen media which is common to all 4 conditions irrespective of screen brightness and the nature of the content, each child will undergo a "control condition weekend" in which the child will participate in the same weekend study protocol, but instead of using screen media in the hour before bed, children will participate in non-screen based quiet activities in room lighting (40-50 lux). The control condition will serve as a negative internal control. The order in which children are exposed to the experimental or control weekends will be randomized (i.e., counterbalanced) to control for possible order effects. Following a week of typical sleep and media use, a 3-day weekend protocol will be implemented in the home facilitated by research staff on two occasions (one week apart, counterbalanced). To assess a potential shift in circadian phase, dim light melatonin onset (DLMO; time at which melatonin level rise above 4pg/mL) will be assessed by research staff on Nights 1 and 3 of the weekend protocol via saliva samples collected under tightly-controlled dim light conditions (i.e., DLMO-Night 3 to DLMO-Night 1). To facilitate the assessment of circadian phases under dim light conditions (\<5 lux), research staff will place temporary covers over windows and adjust the lighting in the child's bedroom. A light meter will be used to ensure appropriate lighting conditions. On Night 2, children will be exposed to either the experimental condition to which they were assigned or the control condition. A background of room lighting (40-50 lux) will be common to both the experimental and control condition. During the experimental condition, children will exposed to screen media according to the experimental condition they were assigned (BL/EC, BL/CC, DL/EC, DL/CC) via a handheld tablet (at eye level, 45 cm in front of the child). To standardize the distance of the iPad from the eye across participants, the tablet (or non-screen-based activity) will be placed on an adjustable bed desk at a distance of 45cm from the eye. Children will sit upright in bed with a pillow behind them. A similar posture will be used in the control condition. Assessments on Night 2, will be as follows: 1) children's sleep will be assessed via actigraphy, 2) children's arousal will be assessed via heart rate (HR), and heart rate variability (HRV) 3)subjective sleepiness ratings will be collected before the start of the experimental condition, after 30 minutes, and again at bedtime. 4) ambient light will be assessed via a light sensor clipped onto the shirt collar. The next afternoon, emotion regulation (subjective reports and respiratory sinus arrhythmia; RSA) and executive functioning (neurocognitive testing) will be measured to assess these secondary outcomes. Research staff (in teams of 2) will be present in the home to conduct the circadian phase assessments, administer the experimental conditions on the Night 2, and to conduct the executive functioning and emotion regulation assessments in the afternoon of Night 3. During the weekend protocols, children will be able to participate in daytime activities as usual with the exception that on days when melatonin is assessed, children will be asked to refrain from strenuous physical activity as this is known to affect melatonin. During the week prior to each weekend assessment, the procedures will be the same for all participants. Parents will select a bedtime and wake time for their child based on their habitual sleep times (+/- 30 mins). Families will be asked to maintain this sleep schedule for the duration of the 2-week protocol, except on nights when DLMO is assessed. Adherence to sleep/wake patterns will be assessed via actigraphy. Because previous exposure to light and screen media can impact future responsiveness to light and screen media, the research team will assess children's ambient light exposure using a reliable sensor clipped near the shirt collar. Mobile device screen use will be assessed using an app downloaded onto the tablet. Other types of screen media use will be assessed by parent report. Variables assessed during the weeks preceding the experimental weekend will be used as covariates in the analysis. While 200 children are needed to be powered to examine the interaction effect of light and content on children's total sleep time, an additional 20 children will be recruited to account for attrition. The total sample size will be up 220 children.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
SINGLE
Enrollment
220
Non-screen-based quiet activities for 1 hour before bed in room lighting 40-50 lux
Bright light screen media exposure will be delivered on an iPad Pro provided by the research team which will be set to the brightest light intensity setting for 1 hour before bed in room lighting 40-50 lux
Filtered dim light screen media exposure will be delivered for 1 hour before bed in room lighting 40-50 lux on an iPad Pro provided by the research team. A blue light filter will be used to alter the spectral distribution of the emitted light and the screen brightness will be dimmed to the lowest possible setting
Children's Nutrition Research Center
Houston, Texas, United States
RECRUITINGDifferences in Sleep Duration on nights following the experimental and internal negative control exposures
Children will wear an Actiwatch Spectrum watch (Philips Respironics, Inc.) on the wrist of their non-dominant hand. Total sleep time are the total minute of sleep scored as sleep by the Sadeh algorithm between sleep onset and sleep offset.
Time frame: Night 9 and 16
Differences in Subjective Sleep Quality on nights following the experimental and internal negative
Visual analog scales will be used to collect subjective ratings of sleep quality and morning alertness the morning following the study condition. Participants will be asked to rate the quality of their sleep last night (very poor to very good), how difficult was it for them to wake up this morning (very easy to very hard), and how alert do you feel right now (wide awake to very sleepy).
Time frame: Night 9 and 16
Differences in the change in circadian phase
Circadian phase can be examined by measuring the circadian timing of melatonin onset under dim light conditions (dim light melatonin onset; DMLO). Following established procedures with children, salivary DLMO will be collected under dim light conditions (\<5 lux), via a cheek swab every 30-60 minutes beginning 5 hours prior to and ending 1-hour following typical bedtime. Saliva samples will be centrifuged, frozen, and assayed using radioimmunoassay test kits by Solid Phase in Portland Me. DLMO phase will be determined using linear interpolation across the time points before and after melatonin concentration increased to and remained above 4pg/mL. We will examine differences in the change from night 8 to night 10 and the change from night 15 to night 17.
Time frame: night 8 to night 10 and night 15 to night 17
Differences in Sleep Latency on nights following the experimental and internal negative control exposures
Children will wear an Actiwatch Spectrum watch (Philips Respironics, Inc.) on the wrist of their non-dominant hand. Sleep latency (i.e., the time between when they child starts to try to fall asleep as indicated by a push of the event marker button on the Actiwatch and when the child falls asleep (first 3 consecutive epochs of sleep).
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We will create a 1-hour recording of movie clips containing exciting content from age-appropriate movies for 8- to 11-year-old children as rated by Common Sense Media.
We will create a 1-hour recording of movie clips containing calming content from age-appropriate movies for 8- to 11-year-old children as rated by Common Sense Media.
Time frame: Night 9 and 16
Differences in Heart Rate during the experimental and internal negative exposures
Heart rate (HR) will be assessed using a Polar H10 HR monitor which integrates with the Actigraph GT3X-BT devices to record HR data from which raw data can be extracted. The Polar H10 HR monitor will be worn on a chest strap fitted to the child according to manufacturer guidelines during the 1-hour experimental and internal negative exposures.
Time frame: Night 9 and 16
Differences in Heart Rate Variability during the experimental and internal negative exposures
Heart rate variability (HRV) will be assessed using a Polar H10 HR monitor which integrates with the Actigraph GT3X-BT devices to record HR data from which raw data can be extracted. The Polar H10 HR monitor will be worn on a chest strap fitted to the child according to manufacturer guidelines during the 1-hour experimental and internal negative exposures.
Time frame: Night 9 and 16
Differences in Pre-sleep arousal scale following the the experimental and internal negative exposures
the Pre-Sleep Arousal Scale for Children (PSAS-C) will be used to assess Children's subjective report of arousal prior to sleep on Night 2. The PSAS-C contains 16 items comprising 2 subscales assessing somatic and cognitive arousal and demonstrated high internal consistency. Items are scored on a Likert scale from 1 to 5 with scores ranging from 16 to 80. Higher scores indicate greater pre-sleep arousal.
Time frame: Night 9 and 16
Differences in Subjective Sleepiness during the experimental and internal negative exposures
The Pictorial Sleepiness Scale is a measure of perceived sleepiness in a given moment that has been validated with individuals 4- to 73-years of age, demonstrating a strong correlation with the Karolinska Sleepiness Scale (r=.72) and the Sandford Sleepiness Scale(r=.94). The use of cartoon faces facilitates the assessment of sleepiness in population with minimal literacy skills. Almost all participants (99%) correctly ranked the faces in order of sleepiness. Children will complete the sleepiness scale before the start of the experimental condition (\~60 minute prior to bedtime), 30 minutes later, and again at bedtime.
Time frame: Night 9 and 16
Differences in Performance on the Trier Social Stress Test following the the experimental and internal negative exposures
To assess objective emotion regulation in the home on Day 3, we will use a modified version the Trier Social Stress Test (TSST), The task will begin with a 5-min baseline segment, during which children will be asked to relax while they listen to a recording of nature sounds (i.e., waves at the beach) in order to collect resting HR and HRV). After this baseline period, children will then engage in a task in which they To assess objective emotion regulation in the home on Day 3, we will use a modified version the Trier Social Stress Test (TSST), The task will begin with a 5- min baseline segment, during which children will be asked to relax while they listen to a recording of nature sounds (i.e., waves at the beach) in order to collect resting HR and HRV). After this baseline period, children will then engage in a task in which they imagine they are giving a speech in front of a class of 20 kids they have never met. Resting and task-based HR and HRV data will be collected.
Time frame: Day 10 and 17
Differences in ratings of subjective emotion regulation following the the experimental and internal negative exposures
Subjective reports of emotional arousal and regulation will also be collected before and after the 5-minute speech task. Children will provide ratings of arousal using the Self-Assessment Manikin (SAM), a widely-used non-verbal pictorial scale that measures arousal associated with a person's affective reaction to a wide variety of situations and stimuli. Emotion regulation will be assessed via a likert-type rating requiring children to indicate how difficult it was to regulate (control) their emotions during the speech task, from ) (not hard at all) to 10 (very hard).
Time frame: Day 10 and 17
Differences in performance on the Letter Number Sequencing subtest of the WISC-V following the experimental and internal negative exposures
Letter-number sequencing Test (WISC-V) asks children to listen to lists of letters and digits and repeat the letters back in alphabetical order, and the digits in ascending numerical order, with the lists increasing in length from 2-8 alphanumeric characters throughout the test. Children will be read three different alphanumeric series for each list lengths, and one point will be awarded for each correct recall, for a total of 21 points. This performance score will be used as a measure of working memory.
Time frame: Day 10 and 17
Differences in Performance on the Delis-Kaplan Executive Function System The Color-Word Inference Test following the experimental and internal negative exposures
The Color-Word Interference Test (D-KEFS) is a standard "Stroop-like" task. Across the two tasks, inhibition and inhibition switching, completion time and errors (4 indicators in total) are used as markers of inhibitory control. The inhibition task is a standard "Stroop-like" task. During inhibition switching, participants also encounter words in colored ink wherein they say the color and inhibit reading the work. However, during some trials, words are enclosed by a box wherein the participant needs to switch to reading, not naming, the color in which it is printed.
Time frame: Day 10 and 17
Differences in Performance on the Delis-Kaplan Executive Function System The Sorting Test following the experimental and internal negative exposures
The Sorting Test (standard form; D-KEFS) has two conditions: free sort, and sort recognition. In free sort, children are given six cards that display both perceptual features and printed words, and asked to sort the cards into two groups, with three cards per group (description), according to as many different concepts or rules as possible (the set has a maximum of eight potential sorts), and to describe the concepts or rules as possible (the set has a maximum of eight potential sorts), and to describe the concepts employed to generate each sort, for a maximum of four minutes. In sort recognition, study staff sort the same set of cards into two groups with three cards per group, and children have a maximum of 45 seconds to identify and describe the correct sorting rule. Composite scores (based on the D-KEFS) scoring system which combines of the number of correct answers (e.g., identifying 'color' was the sort rule, with how comprehensive the description of the sort rule is.
Time frame: Day 10 and 17
Differences in performance on the Psychomotor Vigilance Task
Assesses vigilant attention (reaction time to changes in visual stimuli) and is sensitive to changes in sleep.
Time frame: Day 10 and 17