You're probably tired, is blue light to blame?

What's the deal about avoiding blue lights when you are preparing for sleep?


Adequate sleep. What, exactly, is that? It’s certainly not the same for everyone. The amount of sleep you need depends on your age and on your own physiology. The average adult needs 7-8 hours of sleep, but some people (this is rare!!!) do fine with 5 or 6 hours and some need 9-10 (see our earlier blog on sleep). So, how do you know how much sleep you need? Do an experiment. For several days, go to bed when you are ready – you know when that is, and allow yourself to wake up naturally, whenever that is. If you feel rested, that is how much sleep you generally need.


Of course, feeling rested depends on the quality of sleep, not just how much. Quality of sleep depends on a whole host of factors, such as whether you are sleep-deprived in general, level of stress, certain medications, temperature of the room, sleep disorders, partner movement and sounds, child requirements in the night, menstruation, pain, too much caffeine, and many others reasons. Some of these can be mitigated; others are hard to change. That 2 am feeding is typically non-negotiable!


In the Western world, most adults are sleep-deprived. Many think they can get along just fine on 4

or 5 hours of sleep, and in fact brag about it! Others are juggling many responsibilities, and completing them often takes them into the wee hours of the morning. There are people who are genetically night owls and others who are genetically morning larks. Teenage brains usually shift to later sleep times and struggle to awaken for school. For the night owls with morning jobs or the teenager with early school start times, sleep time is often compromised. Yet sleep has now robustly been shown to be essential to physical vigor, emotional control, cognitive competence, a strong immune system, mental health, and probably some protection against dementia in old age.


Given the demands on us that make getting enough sleep hard, what do you do to make getting to sleep easier. You’ve probably heard by now about “good sleep hygiene.” Cooler bedroom temps, phone outside your room if possible, or at least set to silence notifications during your sleep hours, a bedtime routine, and not looking at computer screens, phone screens, TVs, or most electronic screens in the couple of hours before going to bed. That’s hard when you have homework or work to do after the kids have gone to bed. You can put your phone and computer screens on a “night” setting if they don’t do so automatically. There’s a good reason for this last recommendation!


The brain has several ways to track time of day so that it can put the appropriate sleep-wake cycle in place. One begins in the retina. You normally think of the photoreceptors – the rods and cones – as the cells that detect light. That’s true, of course. But there is another set of cells, a small subset of the group of neurons that normally send signals about light from the retina to the brain, that also are sensitive to light, specifically blue light. These cells have the ability to signal continuously, all during the time that light is on; they fire less as light dims in the evening. As long as they are signaling to the brain center that controls the sleep-wake cycle, the center inhibits entry into the sleep cycle. Electronic screens typically emit lots of blue light and so viewing them at night essentially sends the message that the brain should stay awake. While this is only one of the signals to the sleep-wake center in the brain, it is one that is easily controlled by reducing screen time in the hours before bed, and also darkening your bedroom during sleep time, especially all those LED lights that seem to decorate every single piece of electronic equipment in our homes.


Sleep well!
















Read More:

Walker, M (2017) Why We Sleep New York: Scribner. ISBN 978-1-5011-4431-8



Author: Lynne Oland, PhD

The Center for Neurosciences Foundation

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Tucson, Arizona 85718

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