How Smart Is It to Go to Bed with the Phone? The Impact of Short-Wavelength Light and Affective States on Sleep and Circadian Rhythms.

Sarah R Schmid,Monika Angerer,Belinda Pletzer,Kathrin Bothe,Christopher Höhn,Christina P Plamberger,Kerstin Hoedlmoser

doi:10.3390/clockssleep3040040

Sarah R Schmid, Monika Angerer + Show 5 more

Open Access

https://doi.org/10.3390/clockssleep3040040

Copy DOI

Journal: Clocks & sleep	Publication Date: Oct 28, 2021
Citations: 17	License type: CC BY 4.0

Affiliation: University of Salzburg

Abstract

Previously, we presented our preliminary results (N = 14) investigating the effects of short-wavelength light from a smartphone during the evening on sleep and circadian rhythms (Höhn et al., 2021). Here, we now demonstrate our full sample (N = 33 men), where polysomnography and body temperature were recorded during three experimental nights and subjects read for 90 min on a smartphone with or without a filter or from a book. Cortisol, melatonin and affectivity were assessed before and after sleep. These results confirm our earlier findings, indicating reduced slow-wave-sleep and -activity in the first night quarter after reading on the smartphone without a filter. The same was true for the cortisol-awakening-response. Although subjective sleepiness was not affected, the evening melatonin increase was attenuated in both smartphone conditions. Accordingly, the distal-proximal skin temperature gradient increased less after short-wavelength light exposure than after reading a book. Interestingly, we could unravel within this full dataset that higher positive affectivity in the evening predicted better subjective but not objective sleep quality. Our results show disruptive consequences of short-wavelength light for sleep and circadian rhythmicity with a partially attenuating effect of blue-light filters. Furthermore, affective states influence subjective sleep quality and should be considered, whenever investigating sleep and circadian rhythms.

Highlights

Human sleep is highly vulnerable to external and internal influences
Post-hoc pairwise comparisons indicated that the distal-proximal gradient (DPG) was lower after reading on a smartphone without a filter compared to reading a book at 03:00 (t(29) = −2.54, p = 0.017, d = 1.29), 03:30 (t(29) = −2.35, p = 0.026, d = 1.13), 04:00 (t(29) = −2.40, p = 0.023, d = 0.95) and at 04:30 (t(29) = −2.14, p = 0.041†, d = 0.95; explorative analyses)
This study investigated the impact of evening short-wavelength light on sleep and circadian rhythmicity

Summary

Introduction

Human sleep is highly vulnerable to external (i.e., ambient light) and internal (i.e., affective states) influences. Smartphones and other electronic devices are equipped with light-emitting-diodes (i.e., LEDs), which emit a high proportion of short-wavelength light [5], peaking in wavelengths around 460 nm [6,7]. This is of special interest, as so-called intrinsically photosensitive ganglion cells in the retina (ipRGCs) are expressing the photopigment melanopsin, which is highly sensitive to light of short wavelengths between 446 and 484 nm [8]. It is of importance to discuss potential health hazards due to the circadian effects together with positive aspects of an exposure to light of different wavelengths at different times of the day [13]. Blue-light-blocking glasses were able to attenuate such light-induced effects [16]

Methods

Results

Conclusion