Blue light-blocking glasses may be a gateway to better sleep

Wearing blue light-filtering glasses for at least 2 hours before bedtime may be the solution to a better night's sleep and also a better performance the following day, suggests findings from two studies.

“We found that wearing blue-light-filtering glasses is an effective intervention to improve sleep, work engagement, task performance and organizational citizenship behaviour, and reduced counterproductive work behaviour,” said lead author Dr Cristiano Guarana of Indiana University Bloomington in Bloomington, Indiana, US.

“Wearing blue light-filtering glasses creates a form of physiologic darkness, thus improving both sleep quantity and quality,” he explained.

Participants were randomized to wear either a pair of blue light-filtering glasses or sham glasses as control for 2 weeks, before switching the other pair of glasses. All glasses were worn for at least 2 hours before bedtime each night. The first study involved 63 managers (mean age 36.75 years, 40 percent female) from a multinational financial firm while the second study involved 67 call centre representatives (mean age 31.54 years, 64 percent female) from the same company. [J Appl Psychol 2020;doi:10.1037/apl0000806]   

Wearing blue light-filtering glasses led to significant improvements in both sleep quantity assessed on the Pittsburgh Sleep Diary (p<0.01) as well as sleep quality measured using two items adopted from Karolinska Sleep Diary (p<0.01) compared with control glasses.

Consequently, participants showed better attitudinal aspect towards work as reflected in daily work engagement when they wore blue light-filtering glasses vs control glasses at night.

Furthermore, improvements in behavioural aspects including organizational citizenship behaviour, task performance, and counterproductive work behaviour were also seen during the period blue light-filtering glasses were worn compared with control glasses.

When stratified by chronotypes, the researchers found that the benefit of wearing blue light filtering glasses was greater in participants whose sleep periods were later in the day (night owls) than those with earlier sleep periods (morning larks).

“Although most of us can benefit from reducing our exposure to blue light, owl employees seem to benefit more because they encounter greater misalignments between their internal clock and the externally controlled work time,” Guarana explained. “Our model highlights how and when wearing blue-light-filtering glasses can help employees to live and work better.”

Essentially, the findings support the investigators’ speculation that blue-light exposure is one reason contributing to poor sleep and affected work outcomes.

“Blue-light exposure should also be of concern to organizations,” pointed out Guarana. “The ubiquity of the phenomenon suggests that control of blue-light exposure may be a viable first step for organizations to protect the circadian cycles of their employees from disruption.”

“This study provides evidence of a very cost-effective means of improving employee sleep and work outcomes, and the implied return on investment is gigantic,” said study co-investigator Professor Christopher Barnes from the University of Washington's Foster School of Business in Seattle, Washington, US. “I personally do not know of any other interventions that would be that powerful at that low of a cost.”