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bedroom light causing insomnia

Sleep Hygiene Defined and Why It's Important

Sleep hygiene is the term the sleep medicine community uses to refer to behaviors that impact the quality and quantity of sleep. According to the CDC, one in ten people in the United States has chronic insomnia - that's roughly 32 million Americans! Sleep hygiene, when poor, can be a major contributor to sleep difficulties. When patients report poor sleep quality, one of the things that I always discuss with them is how to tune-up their bedroom for better sleep. 

The Light-Brain Connection 

You may remember from high school biology class that the retina contains rods and cones which help us see. But what your teacher probably didn't tell you is that there is actually a third type of photosensitive cell that is critical for maintaining our normal sleep-wake patterns (circadian rhythms).  Intrinsically photosensitive ganglion cells relay light perception to the body's internal master clock, the suprachiasmatic nucleus, which is embedded deep in the brainstem. 

intrinsically photosensitive retinal ganglion cell

intrinsically photosensitive retinal ganglion cell

These cells are rare, accounting for only about 1% of retinal ganglion cells. They are activated by a specific wavelength of light - 480 nanometers (nm) to be exact - which corresponds to the blue part of the light spectrum. Essentially, when light stimulates the retinal ganglion cells, your brain gets feedback that it's time to wake up. These cells are extraordinarily sensitive to blue light. To give you an example, a person can be nearly 100% blind and these cells will still work to regulate circadian rhythms. This is why "cave-like" sleeping conditions are one of the primary recommendations for sleep hygiene: by keeping your sleep environment completely dark, you are telling your brain it's time to sleep, not wake up.  This can be achieved in various ways:

(1) Black Out the Bedroom

Black Trash Bags

A traditional recommendation has been to adhere black trash bags to all bedroom windows to achieve complete light blockage. This is the most inexpensive approach, but not particularly aesthetically appealing. 

Black Out Window Treatments

This is a great option for those who can afford it. However, you should be aware that the tiniest amount of light seepage above, below or through the window treatments will negate the benefit. 

(2) Manage Internal Bedroom Light

Beware: lights from inside your bedroom such as alarm clocks, phone chargers and other electronics can emit enough blue light to stimulate your photoresensitive retinal ganglion cells. 

(3) Use A Sleep Eye Mask

An alternative (and cost-effective) strategy to blacking out the bedroom is to regularly use a premium eye mask that provides complete blackout. The mask that I personally have used every night for over 3 years, and have found to be extremely comfortable and effective is the Dream Essentials Escape:

dream essentials escape eye mask black


Singular Sleep began to offer Sleep Master masks after I read Tim Ferriss' rave review. There are two models and they have both been top sellers since we added them to our online store:

sleep master mask

Sleep Master Sleep Mask

sleep master deluxe

Sleep Master Deluxe Sleep Mask

 I'll See You on The Dark Side...of The Bedroom

Managing bedroom light is an essential component of overall sleep hygiene. That's why taking the simple steps above to reduce your bedroom light exposure can have a big impact on your sleep quality. Stay tuned as other key aspects of sleep hygiene will be addressed in future articles. 


sleep apnea test home sleep study Joseph Krainin Joseph Krainin, M.D., FAASM is the founder of Singular Sleep, the world's first online sleep center.  He is a Fellow of the American Academy of Sleep Medicine and board-certified in both sleep  medicine and neurology. He has been practicing medicine for over 10 years.

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