Office Windows with Daylight and Views Improve Sleep and Cognition

by | Jun 29, 2020 | 2020, Cognitive Health, Sleep

Written by Joyce Smith, BS. This crossover study explores the effect of optimized levels of daylight on the sleep and cognitive performance of office workers.

sunlightThe maintenance of our circadian rhythms requires environmental exposure to varying degrees of light and dark 1. Light or the absence of it affects the brain’s secretion of cortisol and serotonin that support our daytime activities while our melatonin levels affect our sleep. Past research has demonstrated that when office workers were exposed to minimal natural light during their workday shifts, they tended to experience shorter sleep duration and diminished cognitive ability compared to those who had more daytime sunlight exposure. Adequate and quality sleep affect both our mood and cognitive performance 2-5 and when deficient, sleep is associated with many negative health outcomes in the U.S. Among them are cardio- and cerebrovascular diseases, malignancies, work accidents, diabetes, and hypertension 6. Today, we spend 87% of our time indoors, yet our buildings underutilize the healthful impact of adequate daylight in the workplace and in schools 7. A 2014 study revealed that office workers who received adequate daylight at their workstations slept longer per night than their coworkers  with no office windows 8,  while another study validated that sleep improved (36 minutes longer sleep duration) for children exposed to sunlight from large classroom windows compared to classrooms with very little light.

Thus, researchers, using a case-crossover study design 9, sought to explore the sunlight/sleep connection by determining the differences in sleep patterns for thirty people working in adjacent identical office environments with the exception of lighting and a view. One office had traditional dark fabric roller blinds drawn to obscure 75% of sunlight coming through the large glass windows as well as no outdoor view 10. The second office had no drawn blinds but had windows that were treated with electrochromic glazing technology which allowed more sunlight to pass through while still minimizing glare and provided an outdoor view. For the experiment, typical office workers were asked to work in one office for one week, then switched offices for the following week. Wrist actigraphs (devices for monitoring rest/activity cycles) worn by participants measured and recorded the hours of sleep achieved every night for the two-week period.

After controlling for lifestyle factors that are known to affect sleep (melatonin, evening exercise, number of alcoholic drinks, afternoon caffeine intake, and evening screen time), researchers found that working in the office with optimized daylight conditions increased sleep per night by 37 minutes (p < 0.001) compared to working in the office with blinds. When comparing the effect of individual lifestyle factors, melatonin supplementation was associated with an increased sleep duration of 27 min (p = 0.396), evening exercise with an increased sleep duration of 22.5 minutes (p = 0.137), alcohol consumption with a loss of 2.5 minutes of sleep time per drink (p = 0.796), afternoon caffeine with a loss of 16 minutes (p = 0.316), and a loss of 7 minutes per hour of screen time (p = 0.313). In addition, participants scored 42% higher on cognitive assessments when exposed to optimized daylight and views compared to the roller blinds with restricted daylight and view.

Participants who were categorized as “poor sleepers” had an expected significantly shorter sleep duration in their baseline week; however, they were also the recipients of significantly improved sleep duration when they worked in the office with optimized daylight and view. Starting at a shorter baseline of sleep duration, poor sleepers gained 52.8 minutes of sleep (p < 0.001), while good sleepers, who started at a longer baseline of sleep duration, gained 18.1 minutes of sleep (p = 0.214).

Based on study results, increasing sunlight exposure in office settings may be a practical approach to achieving more optimal circadian rhythms that support improved sleep, cognitive skills, and better health.

Source: Boubekri, Mohamed, Jaewook Lee, Piers MacNaughton, May Woo, Lauren Schuyler, Brandon Tinianov, and Usha Satish. “The Impact of Optimized Daylight and Views on the Sleep Duration and Cognitive Performance of Office Workers.” International journal of environmental research and public health 17, no. 9 (2020): 3219.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open accessarticle distributed under the terms and conditions of the Creative Commons Attribution(CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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