Morning Light = Happier Day

While an upbeat “morning person” might make his/her night owl co-workers pale when faced with all of that unbridled energy, a new report reveals how getting a lot of light in the morning can lead to better sleep and less depression & stress.

[dropcap style=”letter” size=”52″ bg_color=”#ffffff” txt_color=”#f7df04″]W[/dropcap]aking up on the “wrong side of the bed” doesn’t have to set a negative tone for the rest of the day. People who can adjust the timing for experiencing good light earlier in the morning can benefit in unexpected ways.

A new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute found that office workers who receive a robust dose of circadian-effective light in the morning – from either electric lighting or daylight – experience better sleep and lower levels of depression and stress than those who spend their mornings in dim or low light levels.

The LRC research team, led by Dr. Mariana Figueiro, professor and director of the LRC’s Light and Health program, investigated the connection between circadian stimulus (CS) – a measure of light’s impact on the circadian system – and sleep, depression, and stress in office workers. The results were published in the June issue of Sleep Health, the journal of the National Sleep Foundation, in an article titled, “The impact of daytime light exposures on sleep and mood in office workers”— and were featured in a Reuters news story.

[mks_pullquote align=”left” width=”700″ size=”24″ bg_color=”#ffffff” txt_color=”#e56120″] “Our study shows that exposure to high CS during the day, particularly in the morning, is associated with better overall sleep quality and mood scores than exposure to low CS.”

— Dr. Mariana Figueiro


The research involved 109 participants at five office buildings managed by the U.S. General Services Administration (GSA) in various geographic sites such as Washington D.C., Portland, Ore., Seattle, and Grand Junction, Colorado.

Each study participant wore a Daysimeter, a research tool developed by the LRC used in frequent studies to measure the amount of CS a person actually receives, along with their activity patterns. Each participant was asked to wear the Daysimeter as a pendant for seven consecutive days during data collection periods in winter (between December and February) and again in summer (between late May and August). In addition, data was collected that evaluated perceived depression and stress levels as well as sleep quality, logs of bedtimes and wake times including naps, plus other measurement tools.

Dr. Figueiro and her team found that office workers receiving a morning CS of at least 0.3, regardless of source (electric lighting and/or daylight), exhibited greater circadian entrainment, were able to fall asleep more quickly at bedtime, and experienced better quality sleep than those receiving a morning CS of 0.15 or less. The CS – the calculated effectiveness of light’s impact on the circadian system – ranges from 0.1, the threshold for circadian system activation, to 0.7, response saturation.

Participants who received high CS (at least 0.3) in the morning were able to fall asleep faster at bedtime than those receiving low CS (0.15 or less), and this association was even stronger in the winter months. At bedtime, participants receiving low CS lay in bed for approximately 45 minutes before they could actually fall asleep, which can lead to reduced sleep duration for those with a fixed wake time.

Furthermore, participants who received high CS in the morning reported lower levels of stress than those receiving low CS, and this finding was consistent during both summer and winter. While receiving high CS in the morning is hypothetically the most beneficial for entrainment, participants receiving high CS during the entire workday (8:00 a.m. to 5:00 p.m.) experienced better sleep quality and felt less depressed compared to those receiving lower amounts.

“Our study shows that exposure to high CS during the day, particularly in the morning, is associated with better overall sleep quality and mood scores than exposure to low CS,” Figueiro states. “The present results are a first step toward promoting the adoption of new, more meaningful metrics for field research, providing new ways to measure and quantify circadian-effective light.”

“We are supporting this type of research so we can learn more about the connections between lighting and health,” said Bryan Steverson with GSA. “The data from this research will help support our efforts in developing new lighting practices that can optimize health benefits for federal employees working in our federal buildings.”

This study is the first to measure personal circadian light exposure in office workers using a device calibrated to measure circadian-effective light. It is also the first to directly relate circadian-effective light measures to mood, stress, and sleep outcomes. 

Leave a Reply

Your email address will not be published. Required fields are marked *