Blue light makes adolescents more alert

Study shows how blue and red light affects concentration in adolescents.

Do you check your phone in bed in the evening and then wonder why you can’t fall asleep? A number of studies have already dealt with the negative effects media consumption in the evening has on young people’s sleep. One of the reasons for the poor quality of sleep seems to be the blue light emitted by mobile phone screens, as it is similar to the stimulating light at the break of day. Whilst the effects of red and blue light on adults has been relatively well researched, there have hardly been any studies focusing on young people – until now. A team at FAU led by Dr. Petra Studer, neuroscientist, and PD Dr. Oliver Kratz, senior consultant at the Department of Child and Adolescent Mental Health at Universitätsklinikum Erlangen (head of department: Dr. Gunther Moll) has now compared the effects of red and blue light on the sleep and attention of school pupils from Erlangen. The results have been published in the journal ‘Physiology & Behavior’ (vol. 199, pp 11–19).

Can school pupils concentrate and perform better if they are surrounded by light of a particular colour? This is the question investigated by a team led by Dr. Studer and PD Dr. Kratz, who compared the influence of red-enhanced and blue-enhanced light on attention and quality of sleep in adolescents. Approximately 30 school pupils from grammar schools in Erlangen, aged between 11 and 17, took part in the project led by the Department of Child and Adolescent Mental Health at Universitätsklinikum, Erlangen. On two different days, they came to the ‘light laboratory’, a room with bright lighting, where they were exposed once to blue light, and once to red. After 20 to 60 minutes in this environment, the adolescents completed tests aimed at determining how well they could concentrate. They had to complete arithmetic and reading comprehension tasks, and take a computer-based test to determine their attention levels.

Blue in the morning, red in the evening

The researchers came to the conclusion that, similarly to adults, the attention of school pupils increased in blue light, measured on the basis of their mistakes and the consistency of their reactions – in two out of three attention tests they performed better than when exposed to red light. The colour of the light made no difference to reading comprehension, however. Why do the different colours of light affect the ability to concentrate? ‘Our body clock responds to the different shades, which reflect the natural rhythm of day and night,’ explains Dr. Studer. ‘Blue light is reminiscent of the light in the morning and our brain gets into gear, ready to perform throughout the day ahead. Red light, on the other hand, reminds us of the atmosphere of the evening and signalises that it is time for us to unwind and relax. The first results of the study show that adolescents sleep slightly better after being exposed to red evening light rather than blue light.’
This also explains why some people are more likely to have a poorer quality of sleep if they use their mobile phones before going to bed, due in part to the blue light from the screen. Being exposed to this light in the evening leads to our brains being stimulated at the wrong time of day. Some manufacturers offer a night mode for their devices which emits more red colours, aimed at relaxing the eyes and the brain. Dr. Studer and her colleagues hope that their study will encourage further research into the effects of light on attention and sleep in adolescents. Not only that, but it may also lead to new developments such as lighting designed to provide the perfect conditions for focused learning and healthy sleep.

The study can be found (in German) at: www.spektrum.de/news/konzentriert-dank-blauem-licht/1608654

Further information:

Dr. Petra Studer
Phone: +49 9131 85 39123
petra.studer@uk-erlangen.de