SCREENS: Sleep, Circadian Rhythms, and Electronics in the EveNing Study

Differences 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.

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).

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.

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).

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.

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.

Ambient Light Exposure

ActLumus devices containing a photocell will be used to assess ambient light exposure. Devices will be pinned to the shirt. ActLumus devices are capable of assessing light intensity and wavelength. Light exposure will be used as a covariate in analyses.

Average daily duration of Tablet use (excluding the experimental exposures)

Children's tablet use on Android and iOS devices will be assessed during the study period. Daily screen use will be used as a covariate in the analysis.

Other Screen Media Use

To assess for other types of screen use without over burdening parents with screen use diaries that require reporting of screen use in 15-minute increments 24 hours a day, we will add brief questions to the daily sleep diary regarding how much time (hours and minutes) the child spent on other screen devices each day (computer, video games, time spent on siblings or parent's mobile devices, t.v., etc.).

Demographics

Information will be obtained at baseline including child sex at birth and gender, parent sex and gender, parent education, family income, and child race and ethnicity. Family income-to-needs ratio will be calculated.