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 or abnormal sleep patterns, one of the things that I always discuss with them is how to best manage exposure to blue light in the evening.
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 part of the brain that maintains the body's internal clock, the suprachiasmatic nucleus, which is embedded deep in the brainstem.
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 wavelength of the light spectrum. Essentially, when light stimulates the retinal ganglion cells, your brain gets feedback that it's time to wake up. When you are exposed to blue light in the evening, your light suppresses the release of melatonin, the natural sleep-promoting hormone. Your brain normally releases melatonin automatically in dim light. Interestingly, blue light may have farther reaching implications for sleep as shift work has been determined by the World Health Organization to be a probable carcinogen; we believe that this is probably related to excessive exposure to blue light or getting it at a time that our bodies don't want.
Some people have intrinsic and fixed problems with melatonin secretion. Delayed sleep phase disorder is associated with melatonin release later than normal causes difficulty falling asleep and the tendency to sleep in too late. Advanced sleep phase disorder is associated with melatonin being released too early and results in falling asleep and waking up very early. If you think that you might suffer from one of these disorders, you can check your dim light melatonin onset (DLMO) through a saliva test.
The retinal ganglion 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.
What to Do Before Bed
I recommend avoiding blue light for at least one hour prior to your desired bedtime, and two hours is even better. Avoid electronic devices like smartphones, tablets, and computers that emit a lot of blue light. If you just can't stay away from these devices, use a pair of quality blue blocker glasses, a blue blocker screen, or use an app like F.Lux to reduce your exposure to blue light.
In the Bedroom
It's important to make sure that while you're sleeping you're not exposed to light. You'll have to manage external and internal light.
- 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.
- Unplug or turn around electronics in the bedroom so that you can't see any light. Do not sleep with the TV on!
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:
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.