Does one hour of bright or short-wavelength filtered tablet screenlight have a meaningful effect on adolescents’ pre-bedtime alertness, sleep, and daytime functioning?

Abstract

Electronic media use is prevalent among adolescent populations, as is the frequency of sleeplessness. One mechanism proposed for technology affecting adolescents' sleep is the alerting effects from bright screens. Two explanations are provided. First, screens emit significant amounts of short-wavelength light (i.e. blue), which produces acute alertness and alters sleep timing. Second, later chronotypes are hypothesised to be hypersensitive to evening light. This study analysed the pre-sleep alertness (GO/NOGO task speed, accuracy; subjective sleepiness), sleep (sleep diary, polysomnography), and morning functioning of 16 healthy adolescents (M = 17.4 ± 1.9 yrs, 56% f) who used a bright tablet screen (80 lux), dim screen (1 lux) and a filtered short-wavelength screen (f.lux; 50 lux) for 1 hr before their usual bedtime in a within-subjects protocol. Chronotype was analysed as a continuous between-subjects factor; however, no significant interactions occurred. Significant effects occurred between bright and dim screens for GO/NOGO speed and accuracy. However, the magnitude of these differences was small (e.g. GO/NOGO speed = 23 ms, accuracy = 13%), suggesting minimal clinical significance. No significant effects were found for sleep onset latency, slow-rolling eye movements, or the number of SWS and REM minutes in the first two sleep cycles. Future independent studies are needed to test short (1 hr) vs longer (>2 hrs) screen usage to provide evidence for safe-to-harmful levels of screenlight exposure before adolescents' usual bedtime.

Chronotype and environmental light exposure in a student population

“…Of particular interest in this young student population is the impact of light-emitting devices on sleep and the circadian clock. Although such devices have been found to impact sleep and circadian timing (Cajochen et al 2011; Chang et al 2015), the findings are mixed (Heath et al 2014; Rangtell et al 2016) and these changes are often small; thus, the real-world significance of these findings remains unclear (Zeitzer 2015). The findings from this study, however, emphasise that environmental evening light exposure may need to be tailored for different populations.…”

Computer Screen Use Detection Using Smart Eyeglasses

“…Typical TV content caused one-third of the irradiance compared to PC use. Heath et al (2014) found that 1 h of tablet use prior to bedtime did not significantly impact circadian phase. While used at a close distance, smartphones and tablets are not large enough to reach the 50-lx threshold.…”

“…Previous study protocols administered continuous screen use for 1-5 h (Cajochen et al, 2011;Heath et al, 2014;Chang et al, 2015;van der Lely et al, 2015) when investigating circadian phase shifts due to screen use. Wood et al (2013) found measurable melatonin suppression after 2 h of tablet use.…”

“…Possible intervention measures have been investigated (Heath et al, 2014;van der Lely et al, 2015). The latest update of Apple iOS introduced a software feature to adapt screen color profiles to minimize unwanted circadian phase shifts.…”

“…Heath et al (2014) studied if tablet use 1 h prior to bedtime influences the circadian phase. In their study on 16 participants, unfiltered light was compared to light filtered with the f.lux application.…”