New Study Shows that Filtering Blue Light Before Bed Improves Sleep of Adolescents

A study has shown that wearing blue blocking glasses in the evening "prevented light-induced melatonin suppression and alerting effects in young adults, and significantly improved subjective sleep quality after a continuous 2-week application"

The study was undertaken by Swiss scientists and published in the Society for Adolescent Health and Medicine. Researchers were attempting to assess if blocking blue light from multimedia devices would result in a measurable improvement in sleep promoting markers.

Details of the Study 

Thirteen healthy, male, high-school students between 15 and 17 years old were recruited for the study. Half the subjects were given blue blocking glasses and the other half given a clear lens (control group). 

The study was conducted in two phases : the preparatory period and the laboratory period. The first phase of the study lasted a week and subjects participated from their homes. During the first phase, subjects were asked to wear their respective lens for 3 hours before bed, while maintaining their natural rhythm. Both groups were asked to refrain from day-time naps, drinking caffeine and evening outings. Sleep metrics were measured using actimetry and sleep logs.  

The second phase of the study lasted a week and was conducted in a laboratory. The subjects reported to the laboratory 5.5 hours before their anticipated sleep times. These sleep times were carefully recorded during the first phase of the study.

At the laboratory, participants were placed in pre-determined lighting conditions:  

• From 5.5 hours to 3.5 hours before bed, participants placed in a dimly lit room (<8 lux="" with="" no="" group="" wearing="" the="" glasses="" li="">
• From 3.5 hours to 3.0 hours before bed, participants placed in a darkened room with no group wearing the glasses
• From 3.0 hours to bed time in front of a LED-backlit computer with the groups wearing either blue blocking glasses or clear lens. The light in the room was turned off and the computer screen was set to maximum brightness. 

During the 5.5 hour pre-sleep period scheduled tests were conducted to measure salivary melatonin, cognition and subjective sleepiness. Polysomnography was used to measure sleep and wakefulness data during the sleep period. The subjects completed followup tests upon waking.   

Results of the Study

As previously mentioned the purpose of the study was to measure the subjective, physiological and cognitive differences between the control group and the group wearing blue blocking lens. The results of study showed that: 

• Participants reporting feeling significantly sleepier and were less vigilant after wearing blue blocking glasses for the 3 hour period prior to bed time (Graph 1)
• Significantly higher levels of melatonin were measured in participants wearing blue blocking glasses just prior to sleep (Graph 2)
• Participants wearing blue blocking glasses perceived the environment as darker and reported less glare  

Graph 1 : Subjective Sleepiness Level on Karolinska Sleepiness Scale (BB = blue blocking glasses group, CL = clear lens control group)

Graph 2 : Measured Salivary Melatonin Levels (BB = blue blocking glasses group, CL = clear lens control group)

It should be noted the scientist did not observe major differences in the sleep parameters measured during sleep and the subjects morning after reports. 

Significance

The study further confirms that even the relatively low-level light exposure of LED screens is sufficient to suppress the evening melatonin rise and that wearing blue blocking lens prevents this light-induced suppressing effect. 

Although the study was only completed on adolescent boys (thought to be most susceptible to the delaying effects of night time use of electronics) the implications for wider society should be considered. 

General use of electronic devices at night suppresses the natural production of melatonin and results in alerting effects at a time when our bodies should be preparing for sleep. Over a long term this could result in a phase shift of our internal 'circadian night' to a later time period. This is not a problem if we can get up at a later time to accommodate the phase shift. However, people with set wake up times due to employment, school or family obligations are likely to feel the impact of the reduced sleep period. 

The scientists  recommended further tests, however concluded the report with "blue blocking glasses therefore have the potential to acutely impede the negative effects modern lighting imposes on circadian physiology in the evening. The impact on the circadian system implicates that multimedia screen use may be harmful for adolescents' health also in the long run and that blue blocking glasses could serve as a countermeasure with beneficial effects on sleep quality, daytime functioning, and even mood."