Elsevier

Sleep Medicine

Volume 14, Issue 12, December 2013, Pages 1422-1425
Sleep Medicine

Brief Communication
Let there be no light: the effect of bedside light on sleep quality and background electroencephalographic rhythms

https://doi.org/10.1016/j.sleep.2013.09.007Get rights and content

Abstract

Objectives

Artificial lighting has been beneficial to society, but unnecessary light exposure at night may cause various health problems. We aimed to investigate how whole-night bedside light can affect sleep quality and brain activity.

Patients and methods

Ten healthy sleepers underwent two polysomnography (PSG) sessions, one with the lights off and one with the lights on. PSG variables related to sleep quality were extracted and compared between lights-off and lights-on sleep. Spectral analysis was performed to rapid eye movement (REM) sleep and non-REM (NREM) sleep epochs to reveal any light-induced differences in background brain rhythms.

Results

Lights-on sleep was associated with increased stage 1 sleep (N1), decreased slow-wave sleep (SWS), and increased arousal index. Spectral analysis revealed that theta power (4–8 Hz) during REM sleep and slow oscillation (0.5–1 Hz), delta (1–4 Hz), and spindle (10–16 Hz) power during NREM sleep were decreased in lights-on sleep conditions.

Conclusions

Sleeping with the light on not only causes shallow sleep and frequent arousals but also has a persistent effect on brain oscillations, especially those implicated in sleep depth and stability. Our study demonstrates additional hazardous effect of light pollution on health.

Introduction

Exposure to light at night is now considered to be ordinary. Artificial light certainly has beneficial aspects; it has extended the length of productive days of work and recreational activities. However, when it becomes unreasonably excessive, it can be considered as light pollution, negatively affecting human physiology [1]. It may disturb circadian organization; influence neuroendocrine systems; and cause many diseases, such as obesity [2], diabetes mellitus, depression, and even cancers [1].

Artificial lighting also is commonplace in bedrooms, and individuals with poor sleep hygiene often deliberately or unintentionally fall asleep with lights on. For example, one may fall asleep late night with the television light on, and children who are afraid of the dark may ask their parents to keep their lights on during sleep. Light exposure may affect sleep quality, but there have been no systemic comparative studies with objective measures. If any difference exists, it may be reflected in background brain oscillations. Here we performed two whole-night polysomnography (PSG) sessions, one with lights off and one with lights on, to investigate the effect of light on sleep quality and brain activity.

Section snippets

Methods

Ten young healthy volunteers (4 women; mean age, 27 years; range, 21–34 years) participated in our study, which was reviewed and approved by the local internal review committee. All participants gave fully informed written consent. They were all healthy sleepers without major health problems, including no neurologic, psychiatric, or endocrine disorders. Interviews and the Pittsburgh Sleep Quality Index [3] suggested normal and regular sleep–wake habits. First the PSG was performed with the lights

Results

All participants demonstrated normal patterns of sleep. With the lights on, nine participants reported higher scores in subjective feeling of frequent arousals and shallow sleep. We extracted PSG variables (Table 1) that were appropriate in evaluating sleep quality. There was no significant difference in total bed time, total sleep time, or sleep efficiency between lights-off and lights-on sleep. However, constant exposure to dim light affected sleep architecture, increasing the proportion of

Discussion

Unintentional or intentional light exposure during sleep is becoming increasingly more common due to the widespread use of artificial lighting, and its negative effect on health is a major theme of research. Whole-night light exposure demonstrated acute effects on sleep architecture and brain activity, including shallow sleep, frequent arousals, and reduction of power in SWA and spindle frequency bands during NREM sleep and theta frequency bands during REM sleep.

Light is the major synchronizer

Funding sources

This study is supported by a Grant of the Korean Health Technology R&D Project, Ministry for Health, Welfare & Family Affairs, Republic of Korea (No. A110097) and by a grant of the Korea Healthcare technology R&D Project, Ministry of Health and Welfare, Republic of Korea (HI10C2020).

Conflict of interest

The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2013.09.007.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

Acknowledgment

The authors appreciate the effort of volunteers and technicians in their sleep clinic.

References (16)

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