The blue light emitted by our smartphones, computers and a lot of other screens around us are hurting our sleep. We figured as much, but now it's scientific.
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Short-wavelength blue light damages both duration and crucially, the quality of our sleep, says a joint study by the University of Haifa and Assuta Sleep Clinic. The study was a small one, but its findings fit with previous research. And maybe it all explains why modern man is so short-tempered.
Red light screens don't do a thing to our sleep, the researchers say.
“The solution? Stop doing that before sleep, or use filters to block the harmful radiation," suggests Prof. Abraham Haim of Haifa University.
Maybe the worst bit is that the blue light significantly disrupts the continuity of sleep, say the scientists. If after exposure to red light, people woke an average of 4.5 times a night without noticing, after blue light, they awoke 6.7 times on average.
Previous studies have found that blue light with wave lengths of 450-500 nanometers suppresses the production of melatonin, a hormone secreted at night that is associated with body and sleep cycles.
The study participants were 19 healthy adults aged 20 to 29 and crucially, they did not know the purpose of the study. Knowing you're being studied for sleep patterns is a good way to stay awake.
Their sleeping patterns were measured by self-reporting and using actigraphs for one week (devices that record when you fall asleep and wake up).
In the second part of the trial, at Assuta’s Sleep Laboratory, the participants were exposed to computer screens from 9 p.m. to 11 p.m., which are the hours of night that the pineal gland typically begins to produce melatonin.
Then the participants were exposed to four types of light: high-intensity blue light, low-intensity blue light, high-intensity red light, and low-intensity red light, and their quality and duration of sleep were gauged by instruments that measure brain waves, and questionnaires.
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Long story short: exposure to blue light reduced the duration of sleep by about 16 minutes, on average. Doesn't sound too earth-shattering, but it also significantly reduced the production of melatonin – which means, say the scientists, that the body's biological clock and natural mechanisms are badly disrupted.
Just one example is that blue light prevents the body from activating the natural mechanism that lowers body temperature ahead of sleep.
“Naturally, when the body moves into sleep it begins to reduce its temperature, reaching the lowest point at around 4:00 a.m. When the body returns to its normal temperature, we wake up,” Haim explains. “After exposure to red light, the body continued to behave naturally, but exposure to blue light led the body to maintain its normal temperature throughout the night – further evidence of damage to our natural biological clock.”
In short, after blue light exposure, people report waking up more tired and cranky. Knowing that and getting good filters or changing your habits could save your marriage.
The new study, published in the journal Chronobiology International, was undertaken by researchers Haim, head of the Israeli center for interdisciplinary research in chronobiology at the University of Haifa; doctorate student Amit Shai Green of the Center for Interdisciplinary Chronobiological Research at the University of Haifa and the Sleep and Fatigue Center at Assuta Medical Center; Dr. Merav Cohen-Zion of the School of Behavioral Sciences at the Academic College of Tel Aviv-Yafo; and Prof. Yaron Dagan of the Research Institute for Applied Chronobiology at Tel Hai Academic College.