Effects of smartphone use with and without blue light at night in healthy adults: A randomized, double-blind, cross-over, placebo-controlled comparison
Introduction
Smartphones have become ubiquitous in daily life. The average smartphone use time is increasing and nearly doubled from 98 min in 2011 to 195 min in 2013 (Sale and Scott, 2014). A nationwide community survey conducted in the United States reported that 39% of Americans used cell phones in their bedroom in the hour prior to sleep; the rate was twice as high in adolescents and young adults (Gradisar et al., 2013). Smartphones are often equipped with a light-emitting diodes (LED) display, which delivers bright light to the human eye. Smartphone LED light is an important source of artificial light at night (ALAN). ALAN influences the circadian regulation of the sleep-wake cycle (Gonzalez and Aston-Jones, 2006), suppresses melatonin secretion (Czeisler et al., 1995, Lewy et al., 1980), alters mood and cognitive functions (LeGates et al., 2012), and contributes to fatigue (Meesters and Lambers, 1990).
Advantages of LED display over incandescent light sources include lower energy consumption, longer lifespan of electronic devices. However, LED-based light sources differ from traditional lamps in that they contain higher proportions of short-wavelength blue light ranging from 450 to 470 nm, which is more likely to cause problems, such as blue light hazard, when people look directly into these bright and point-like sources at night (Federation of National Manufacturers' Associations for Luminaires and Electrotechnical Components for Luminaires, 2011). Blue light hazard is defined as the potential for a photochemical induced retinal injury resulting from electromagnetic radiation exposure of short-wavelength blue light (Algvere et al., 2006).
Also, compared to light with longer wavelengths, light of short wavelength has been shown to have a larger suppressing effect on melatonin concentrations (Brainard et al., 2001, Cajochen et al., 2005). Not all studies have found effects of melatonin suppression when blue light devices have been used at night (Heath et al., 2014, Wood et al., 2013). However, Wood et al. mentioned that exposure to blue light LED of self-luminous tablets significantly reduced melatonin levels after 2 h, compared to orange LED (Wood et al., 2013).
Blue light therapy in the morning may be effective for the treatment of depression with a seasonal pattern (Gagne et al., 2011) and depression among the elderly (Lieverse et al., 2011), but blue light exposure at night and in relatively low room light conditions increases secretion of human melatonin and can thus lead to insomnia (Chellappa et al., 2013) and increased vigilance among night workers (Sasseville et al., 2006). Smartphone users exposed to bright blue light from the phone's LED display at night may be affected as well. However, no previous controlled studies have addressed this issue.
The purpose of the present study was to investigate the impact of smartphone LED displays with blue light at night, compared to LED displays with suppressed blue light. The two types of LED displays were indistinguishable from each other with the naked eye because other wavelengths were used to mimic blue light in the suppressed LED. The main hypothesis was that exposure to a smartphone LED display with blue light at night suppresses melatonin increase, decreases sleepiness, and impairs cognitive performance, compared to the effects of the smartphone LED display without blue light.
Section snippets
Subjects
Subjects were recruited through advertisement. All study subjects were recruited at the Samsung Medical Center from September 2013 to February 2014 through web postings and online advertisements. Eligibility for the study was assessed with an in-person interview using the Structured Clinical Interview for DSM-IV Disorders (SCID) (First et al., 1995), self-reported medical history, a series of self-report questionnaires, and physical examinations. All subjects participated voluntarily. In order
Psychiatric and cognitive changes
The 22 men enrolled in the study completed two 3-day admissions at the Clinical Research Center. Their profiles are summarized in Table 1. Mean age was 30.95 ± 4.15 years.
In the between group comparison, subjects who used smartphones with blue light showed significantly decreased sleepiness (Cohen's d = 0.49, Z = 43.50, p = 0.04) and confusion-bewilderment (Cohen's d = 0.53, Z = 39.00, p = 0.02), and increased commission error (Cohen's d = −0.59, t = −2.64, p = 0.02) after smartphone use,
Discussion
This is the first controlled study to investigate the influence of the exposure of blue light from smartphone LED displays at night on humans. The study used newly developed smartphones that suppressed blue light from the LED display, with a screen appearance that was otherwise identical to the conventional blue light LED smartphone. Exposure to the blue light LED display at night decreased user sleepiness and confusion-bewilderment, and increased commission errors. Also, blue light LED
Role of funding source
The sponsors had no role in the analysis of the data, the writing of the report, or the decision to submit the paper for publication.
Contributors
Prof. Hong Jin Jeon was a principal investigator of this study, designed the study, and educated and supervised the interviewers, and checked the whole data. Dr. Jung-Yoon Heo and Dr. Kiwon Kim, Dong Jun Kim, Kyung-Ah Judy Chang, Yunhye Oh, Bum-Hee Yu and Min-Ji Kim wrote the manuscript and analyzed the data. Prof. Maurizio Fava, David Mischoulon, and George I. Papakostas checked the results and supervised the analysis and manuscript.
Disclosure of any conflicts of interest
Dr. Fava has received research support from Abbott Laboratories, Alkermes, Aspect Medical Systems, Astra-Zeneca, BioResearch, BrainCells, Inc., Bristol-Myers Squibb Company, Cephalon, Clinical Trial Solutions, LLC, Eli Lilly & Company, EnVivo Pharmaceuticals, Inc., Forest Pharmaceuticals Inc., Ganeden, GlaxoSmithKline, J & J Pharmaceuticals, Lichtwer Pharma GmbH, Lorex Pharmaceuticals, NARSAD, NCCAM, NIDA, NIMH, Novartis, Organon Inc., PamLab, LLC, Pfizer Inc, Pharmavite, Roche, Sanofi-Aventis,
Acknowledgements
This research was supported by Samsung Display (S-2014-1823-000). This research was also supported by the Original Technology Research Program for Brain Science through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. NRF-2016M3C7A1947307; PI, Hong Jin Jeon), and by a grant of the Korean Mental Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (No. HM14C2567) (PI: Hong Jin Jeon). The authors thank the
References (56)
- et al.
Exposure to bright light is associated with positive social interaction and good mood over short time periods: a naturalistic study in mildly seasonal people
J. Psychiatr. Res.
(2008) - et al.
Thyroid stimulating hormone and serum, plasma, and platelet brain-derived neurotrophic factor during a 3-month follow-up in patients with major depressive disorder
J. Affect Disord.
(2014) - et al.
Circadian rhythms, sleep, and the menstrual cycle
Sleep. Med.
(2007) - et al.
The Pittsburgh Sleep Quality Index: a new instrument for psychiatric practice and research
Psychiatry Res.
(1989) - et al.
Let there be no light: the effect of bedside light on sleep quality and background electroencephalographic rhythms
Sleep. Med.
(2013) - et al.
Bedtime mobile phone use and sleep in adults
Soc. Sci. Med.
(2016) - et al.
Impact of blue vs red light on retinal response of patients with seasonal affective disorder and healthy controls
Prog. Neuropsychopharmacol. Biol. Psychiatry
(2011) - et al.
Effects of nocturnal bright light on saliva melatonin, core body temperature and sleep propensity rhythms in human subjects
Neurosci. Res.
(2002) - et al.
Impact of menstrual cycle phase on endocrine effects of partial sleep restriction in healthy women
Psychoneuroendocrinology
(2014) - et al.
Menstrual cycle effects on cortisol responsivity and emotional retrieval following a psychosocial stressor
Hormones Behav.
(2015)
Light therapy in patient with seasonal fatigue
Lancet
Using blue-green light at night and blue-blockers during the day to improves adaptation to night work: a pilot study
Prog. Neuropsychopharmacol. Biol. Psychiatry
Environmental light and suprachiasmatic nucleus interact in the regulation of body temperature
Neuroscience
The effect of hormone therapy on serum melatonin concentrations in premenopausal and postmenopausal women: a randomized, double-blind, placebo-controlled study
Maturitas
Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression
Appl. Ergon.
Age-related maculopathy and the impact of blue light hazard
Acta Ophthalmol. Scand.
Diagnostic and Statistical Manual of Mental Disorders
Protective effect of blue-light shield eyewear for adults against light pollution from self-luminous devices used at night
Chronobiol Int.
Two types of melanopsin retinal ganglion cell differentially innervate the hypothalamic suprachiasmatic nucleus and the olivary pretectal nucleus
Eur. J. Neurosci.
A comparison of blue light and caffeine effects on cognitive function and alertness in humans
PLoS One
Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor
J. Neurosci.
Effects of amoxapine and imipramine on evoked potentials in the Continuous Performance Test in patients with affective disorder
Neuropsychobiology
2011. Evening exposure to a light-emitting diodes (LED)-backlit computer screen affects circadian physiology and cognitive performance
J. Appl. Physiol.
High sensitivity of human melatonin, alertness, thermoregulation, and heart rate to short wavelength light
J. Clin. Endocrinol. Metabolism
Acute exposure to evening blue-enriched light impacts on human sleep
J. Sleep. Res.
Exposure to dim artificial light at night increases REM sleep and awakenings in humans
Chronobiol Int.
The reliability and validity of the Korean version of the Epworth sleepiness scale
Sleep Breath.
Effects of artificial light at night on human health: a literature review of observational and experimental studies applied to exposure assessment
Chronobiol Int.
Cited by (120)
Luminous characteristics of RGBW mini-LED integrated matrix devices for healthy displays
2024, Optics and Laser TechnologyEffects of outdoor artificial light at night on human health and behavior: A literature review
2023, Environmental Pollution