Sound Sleep Guru

Blue Light and Sleep

A lot of products are emerging on the market for blocking blue light. What is all the hype about blue light?

There are a group of cells in the retina responsible for transmitting non-image related information to the brain. ⁣⁣These retinal ganglion cells are most sensitive to blue light at a frequency of 480 nm with other frequencies being less sensitive. ⁣⁣These cells connect with the master clock in the brain (aka suprachiasmatic nucleus) via the retinohypothalamic tract to entrain the sleep-wake cycle as well as other clocks.⁣⁣ Light is the most potent zeitgeber, which has differing effects depending on when in the sleep-wake cycle it is delivered. ⁣⁣When it comes to sleep initiation insomnia it is important not to get too much light in the evening because it has the effect of delaying sleep onset. Since the retinal ganglion cells are most sensitive to blue light, wearing blue light blocking glasses is a way to mitigate this effect.⁣⁣On the other hand, light exposure in the morning can advance the sleep-wake cycle (shift earlier). ⁣⁣These concepts can be applied depending on the relevant scenario. Light exposure can also help stabilize and reinforce a sleep-wake cycle maintaining regularity. ⁣⁣In our 24/7 technology-driven society we sleep less than any of our ancestors. The ubiquitousness of light has made us almost unaware of the potent effect it has on our bodies and our health. I think of the SCN as the conductor of an orchestra that synchronizes all of our other organ systems to function optimally. The timing of light exposure is central to not only the sleep-wake cycle but the entire body. ⁣⁣In my field, we have a way of estimating and characterizing light exposure with a tool called actigraphy. ⁣⁣These concepts are extremely helpful as non-pharmacological strategies for treating several sleep disorders.⁣

Have you experienced living without electricity – completely in sync with the rhythm of sunrise and sunset?

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