Research News

Light conditions in the morning before waking up affect restfulness

Amount of natural light affects wakefulness

Moderate amounts of sunlight before waking up can have a positive effect.

Credit: Osaka Metropolitan University

Sleep is a necessary part of people’s daily routine, but modern lifestyles and technology have ushered in an era of decreased rest time and subsequent fatigue. Further, the bedroom environment, such as light, sound, and temperature, is important for a good night's sleep, though this is often neglected in residential architecture.

In search of a conclusive remedy, common sleep studies use artificial light that is easy to control. Osaka Metropolitan University researchers, however, believe natural light could be more effective for re-creating actual living environments.

To test this, Graduate School of Human Life and Ecology student Xiaorui Wang and Professor Daisuke Matsushita led a team in examining whether introducing moderate light into the bedroom just before waking would improve morning wakefulness. Using light-shielding curtains and motorized closing devices, a comparative experiment was conducted on 19 participants under three conditions: natural light for 20 minutes before waking up (IA), natural light from dawn until waking up (IB), and no natural light before waking up (CC). After each session, participants’ sleepiness, alertness, and fatigue were measured with an electrocardiogram, electroencephalogram, and a survey.

Results revealed that participants were less sleepy in IA and IB conditions than in CC. In addition, IA was found to be one of the most effective methods for improving wakefulness, as too much light in IB caused adverse effects.

“In the future, we hope to control natural light in the sleep environment as it changes with the seasons and time of day, and to clarify how to introduce natural light that is suitable for a more comfortable awakening,” stated Professor Matsushita.

The findings were published in Building and Environment.

Funding

This study was supported by JSPS KAKENHI [Grant Number 21H01509, 24K01053], and JST SPRING [Grant Number JPMJSP2139].

Paper information

Journal: Building and Environment
Title: Natural light control to improve awakening quality
DOI: 10.1016/j.habitatint.2024.103250
Authors:  Xiaorui Wang, Yangcheng Gu, Jihui Yuan, Daisuke Matsushita
Published: 14 February 2025
URL: https://www.doi.org/10.1016/j.buildenv.2025.112733

Contact

Daisuke Matsushita
Graduate School of Human Life and Ecology
Email: matsushita[at]omu.ac.jp

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