Published: 07 December 2015

Ways to reduce the effect of light-emitting devices on sleep, according to study conducted at the University of Surrey

A new study from the University of Surrey, published 13 October in Frontiers in Public Health, has found that preventative strategies may reduce the adverse effects of light-emitting devices on sleep.

The displays of LE devices often generate substantial short-wavelength blue light emissions in an effort to enhance the efficiency, brightness and contrast of LE screens when used during the day. However, it has been found that these blue-enriched light emissions can also adversely affect sleep as they suppress night-time melatonin and increase alertness.

Research conducted by the Chronobiology Team at The Faculty of Health and Medical Sciences at Surrey, set out to measure short-wavelength light emissions from everyday LE devices. Working alongside Guy’s and St Thomas’s NHS Foundation Trust, researchers also worked towards determining the impact of strategies designed to reduce these blue-enriched light emissions.

Researchers assessed the spectral power of a tablet, e-reader and smartphone when displaying identical text. They also compared the text output with that of Angry Birds, a popular gaming app.

Their tests found that all LE devices tested shared very similar short-wavelength peaks when displaying text, and were all bright and characterised by short-wavelength blue-enriched emissions. However, since this type of light is likely to delay sleep time and cause the most disruption to sleep, these brighter and bluer emissions were deemed inappropriate for night-time use of LE devices.

Finally, the researchers measured the impact of two strategies that claimed to reduce the output of short-wavelength blue light emissions. The first solution tested was an inexpensive and commercially available pair of orange-tinted glasses, thought to block blue-enriched light. The second strategy tested was that of an app which was “sleep-aware”, meaning its designers had deliberately made attempts to reduce its short-wavelength light emissions. After extensive testing, both the orange-tinted glasses and the “sleep-aware” app were found to significantly reduce sleep-disruptive blue light emissions.

The research concluded that there needed to be recognition that at night-time “brighter and bluer” was not necessarily “better” and Professor Debra J. Skene, of Surrey’s School of Biosciences and Medicine, commented: “There is a need to find practical, inexpensive ways to reduce the amount of short-wavelength blue light emitted by everyday LE devices.”

The study, published 13 October in Frontiers in Public Health, established that future software should ideally be better optimised when night-time use is anticipated, and hardware should allow an automatic “bedtime mode” that shifts from blue to yellow and red light emissions.

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