People who work in offices lit by natural light sleep 37 minutes more

People who work in offices lit by natural daylight sleep for 37 minutes more per night and are better at making strategic decisions, study shows

  • Volunteers spent a week working in a poorly lit office and a week in a well lit one
  • They were all asked to wear sleep tracking devices and complete cognitive tests
  • After one day those in the well-lit office were sleeping and performing better 

An office full of natural daylight, rather than artificial light, can help boost decision making skills and help workers get 37 minutes more sleep at night, study shows.

Researchers from the University of Illinois had 30 office staff work in either a room with the windows partially covered or one that let in more natural light.

Volunteers spent a week working in one office, with a fabric blind covering three-quarters of its window, then a week in a one with electronically-tinted glass.

After a week working in the room with the electrochromic glass – which can be tinted to let the maximum natural light while minimising glare – participants slept better at night. 

Study authors found that having access to natural daylight during the working day also led to people scoring 42 per cent higher on strategic thinking tests than they did while in the office with lower levels of natural light.

Researchers from the University of Illinois had 30 office staff work in either a room with the windows partially covered (left) or one that let in more natural light (right)

The study was carried out by Professor Mohamed Boubekri and a team of researchers at the University of Illinois School of Architecture.

‘A growing awareness has recently emerged on the health benefits of exposure to daylight and views,’ the team wrote. 

They said that daylight exposure is linked to circadian rhythm regulation, which can have significant impacts on sleep quality and cognitive function. 

Views of nature have also been shown to impact people’s emotions and performance.  

This study explored the impact of optimised daylight levels on the sleep and cognitive performance of office workers. 

The two offices were identical in furnishings and layouts – the only difference was the amount of light the workers were exposed to.  

Participants in the optimised daylight office slept 37 minutes longer than they did when working in the lower-light level office.

This was measured by wrist-worn devices that tracked their sleep patterns.

Volunteers were split into two groups – the first group started in the poorly-lit office, the other started in the well-lit space. They switched places after a week.

They were selected for each of the two groups based on having a similar set of demographics in terms of sex, age, education, race, job function and health. 

‘Both sleep and cognitive function were impacted after one day in the space,’ the study authors wrote in a paper on the findings.

They said that the impacts became more significant over the course of the week. 

‘The positive effect of optimised daylight and views on cognitive function was comparable for almost all participants,’ they found.

Increases in sleep duration were significantly greater for those with the lowest baseline sleep duration. 

So those that usually slept the least had the biggest improvement in their sleep pattern – when compared to people who usually get a good night sleep.

‘This study stresses the significance of designing with daylight in order to optimize the sleep quality and performance of office workers,’ said Boubekri. 

The team say that our circadian rhythm that influences our sleep and wake cycle gets its clues from the daily light and dark patterns from our environment.

In the modern world we spend 87 per cent of our time indoors and so that lighting should mirror the characteristics of light provided by the natural environment.

The layout of the two officers were identical apart from the type of window covering and the amount of natural light available to the workers

That includes its intensity, spectral characteristics, timing and exposure duration.

Sleep quality and quantity are important health indicators much like our vital signs as they impact our mood, cognitive performance, and a variety of other health outcomes.

Deficient sleep has been associated with leading causes of death in the United States, the authors wrote in their paper.

This including cardiovascular disease, malignant neoplasms, cerebrovascular disease, work accidents, diabetes, and hypertension, among others.

This isn’t the first time researchers have examined the impact increased exposure to daylight can have on sleep patterns.

An unrelated study looked at daylight in a primary school classroom and found those children exposed to daylight through a large window slept 36 minutes longer than those with little daylight during the school day.

‘Electric lighting solutions alone cannot provide the necessary light levels for circadian rhythm entrainment without excessive energy consumption,’ they said.

‘Harnessing and optimizing daylight exposure therefore presents a practical approach for achieving proper circadian rhythm entrainment and by doing so, unlocks significant potential to positively impact occupant health while meeting sustainability goals,’ according to Boubekri and colleagues.

‘Developers and architects should consider the substantial benefits of access to daylight and views when designing, constructing, and renovating office buildings.’ 

The research has been published in the International Journal of Environmental Research and Public Health. 

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