A new study from the Haifa University and Assuta's sleep lab shows that the blue light emitted from screens harms the length and quality of sleep.
The study also found that screens which emitted red light did not harm sleep, and those sleeping near them experienced sleep similar to normal sleep.
"The light emitted from most screens - computers, smartphones, tablets - is blue light, and harms the body's rhythm and sleep cycles. The solution is to use the filters which prevent the blue light emissions," said study co-author Haifa University Professor Abraham Haim.
Previous studies showed that exposure to blue light on radio wavelengths shorter than 450-500 nanometers harms the production of melatonin - the hormone which your body secretes during sleep and which controls the body's sleep-wake rhythms and healthy sleep. The current research, which was published in Chronobiology International, investigated whether there was a difference in sleep patterns when people were exposed to blue light versus red light before going to sleep.
19 people participated in the study, all of them aged 20-29. None of them knew what the purpose of the study was. In the first section, participants wore an actigraphy monitoring system, which recorded the time they went to sleep and woke up. They also filled in a sleep chart and questionnaire on their sleep habits.
The second part of the research included a sleep lab at Assuta, where participants were exposed to screens between the hours of 9 and 11p.m. These hours were chosen because they are when the pineal gland begins to make melatonin.
Participants were exposed to four types of lights: Strong blue lights, weak blue lights, strong red lights, and weak red lights. After their exposure to the lights, participants were hooked up to machines which read their brain waves and were able to determine the sleep stages they went through during the night, and whether they woke up. In the morning, participants filled in a questionnaire about how they felt after the night's sleep.
The study showed that while red lights produced results similar to normal sleep (before which no screens were viewed), blue lights of both frequencies harmed the quality of sleep. It also found that strong blue lights harm sleep more than weak blue lights, but the difference between them is much less than the difference between red and blue lights. What this means is that the wavelength is what makes a difference, not the quality of the light.
"Body temperature drops during sleep, until it reaches its lowest point at around 4:00a.m," Haim said. "From there the temperature rises, and when it reaches its normal temperature, we wake up. Those exposed to red light continued this cycle as usual, but exposure to blue light caused the body to retain its usual temperature during the entire duration of sleep. It's one more proof that this light harms our body's rhythm."
"Exposure to screens during the day and especially during the night is an integral part of life today, and it will only become stronger. In this study, we found that it's not the screens which harm the body's biological clock and our sleep cycles - it's the blue light that they emit. Thankfully, there are apps which filter the problematic blue light and place a red light filter on the screen. This helps lower the harm caused by melatonin suppression."