PeerScreen Trial - Reducing Screen Media Use in Peer-groups of Young People

Self-reported mental well-being assessed as change in total score on the 14-item Warwick-Edinburgh Mental Wellbeing Scale (WEMWBS). Total scores range from 14 to 70 points. Higher scores indicate better mental well-being.

Face-to-face social interaction with peer-group members will be assessed as the total duration of proximity events, expressed in minutes per week, using Bluetooth Low Energy (BLE) beacon data collected via the SDU Connect application. The application logs the frequency and duration of proximity events between participants within a predefined distance threshold. The outcome measure is the change in weekly minutes of peer-group proximity from the 14-day baseline period before randomization to the final 21 days of the intervention period.

Face-to-face social interactions with individuals outside the participant's household and peer group will be assessed using daily self-report collected via the SDU Connect application. These interactions include, for example, family members not living in the household, other friends, and other relations. The outcome measure is the change in the average weekly frequency of self-reported face-to-face social interactions from the 14-day baseline period before randomization to the final 21 days of the intervention period.

Total sleep time will be assessed using continuous monitoring with the Garmin Venu 4 wearable device. Total sleep time will be derived using the device's sleep algorithm and expressed as average minutes of sleep per night. The outcome measure is the change in average nightly total sleep time from the 14-day baseline period before randomization to the final 21 days of the 4-week intervention period.

Physical activity will be assessed using continuous monitoring with the Garmin Venu 4 wearable device. Physical activity will be expressed as average number of steps per day derived from the device. The outcome measure is the change in average daily step count from the 14-day baseline period before randomization to the final 21 days of the 4-week intervention period.

Heart rate variability during sleep will be assessed using continuous monitoring with the Garmin Venu 4 wearable device. Heart rate variability will be expressed as the root mean square of successive differences (RMSSD) in milliseconds (ms), derived from the device during sleep periods. The outcome measure is the change in average nocturnal RMSSD from the 14-day baseline period before randomization to the final 21 days of the 4-week intervention period.

Sleep quality will be assessed using the Garmin Sleep Score (proprietary overall sleep score) derived from continuous monitoring with the Garmin Venu 4 wearable device. Garmin Sleep Score is a device-derived composite sleep measure ranging from 0 to 100 points, with higher scores indicating better sleep quality. The outcome measure is the change in average nightly Garmin Sleep Score from the 14-day baseline period before randomization to the final 21 days of the 4-week intervention period.

Physical activity intensity will be assessed using continuous monitoring with the Garmin Venu 4 wearable device. Moderate-to-vigorous physical activity will be expressed as average minutes per day spent participating in moderate-to-vigorous intensity physical activity, derived from the device. The outcome measure is the change in average daily minutes of moderate-to-vigorous physical activity from the 14-day baseline period before randomization to the final 21 days of the 4-week intervention period.

Physiological synchrony will be assessed as similarity in heart rate time series between dyads of peer-group members during periods of co-presence identified by Bluetooth Low Energy (BLE) beacon data. Heart rate will be measured continuously using Garmin Venu 4 wearable devices. Synchrony will be quantified using a Time Warp Edit Distance (TWED)-based dissimilarity measure applied to dyadic heart rate time series during beacon-defined co-presence periods, with lower dissimilarity indicating greater physiological synchrony. The outcome measure is the change in average dyadic heart rate synchrony from the 14-day baseline period before randomization to the final 21 days of the 4-week intervention period.

Perceived stress will be assessed using the 4-item Cohen Perceived Stress Scale (PSS-4). The PSS-4 total score will be used, with higher scores indicating greater perceived stress. Outcome data will be collected at baseline, post-intervention, and long-term follow-up.

Social connectedness will be assessed using the Friendship Scale. The outcome measure is the total Friendship Scale score at baseline (Day 1), post-intervention (Day 42), and long-term follow-up (Day 70). Higher scores indicate greater social connectedness.

Loneliness will be assessed using the UCLA 3-Item Loneliness Scale. The outcome measure is the total UCLA 3-Item Loneliness Scale score at baseline (Day 1), post-intervention (Day 42), and long-term follow-up (Day 70). Higher scores indicate greater loneliness.

Life satisfaction will be assessed using Cantril's Ladder. The outcome measure is the self-reported Cantril's Ladder score at baseline (Day 1), post-intervention (Day 42), and long-term follow-up (Day 70). Higher scores indicate greater life satisfaction.

Depressive symptoms will be assessed using the Mood and Feelings Questionnaire Short Form (MFQ-SF). The outcome measure is the total MFQ-SF score at baseline (Day 1), post-intervention (Day 42), and long-term follow-up (Day 70). Higher scores indicate greater depressive symptom severity.

Anxiety symptoms will be assessed using the Generalized Anxiety Disorder 2-Item scale (GAD-2). The outcome measure is the total GAD-2 score at baseline (Day 1), post-intervention (Day 42), and long-term follow-up (Day 70). Higher scores indicate greater anxiety symptom severity.

Sleep disturbance will be assessed using the PROMIS Pediatric Sleep Disturbance Short Form 8a. The outcome measure is the total PROMIS Pediatric Sleep Disturbance Short Form 8a score at baseline (Day 1), post-intervention (Day 42), and long-term follow-up (Day 70). Higher scores indicate greater sleep disturbance.

Problematic smartphone use will be assessed using the Smartphone Addiction Scale-Short Version (SAS-SV). The outcome measure is the total SAS-SV score at baseline (Day 1), post-intervention (Day 42), and long-term follow-up (Day 70). Higher scores indicate greater problematic smartphone use.

Mood will be assessed using a self-reported visual analogue scale (VAS) administered daily during the 14-day baseline period before randomization and daily during the 42-day intervention period. The outcome measure is the change in daily mood scores from the 14-day baseline period before randomization to the final 21 days of the intervention period, with higher scores indicating more positive mood.

Stress will be assessed using a self-reported visual analogue scale (VAS) administered daily during the 14-day baseline period before randomization and daily during the 42-day intervention period. The outcome measure is the change in daily stress scores from the 14-day baseline period before randomization to the final 21 days of the intervention period, with higher scores indicating greater perceived stress.

Sleepiness will be assessed using a self-reported visual analogue scale (VAS) administered daily during the 14-day baseline period before randomization and daily during the 42-day intervention period. The outcome measure is the change in daily sleepiness scores from the 14-day baseline period before randomization to the final 21 days of the intervention period, with higher scores indicating greater sleepiness.