Light and Circadian Rhythm

Lots of people have sleep difficulty and depression-like symptoms in the middle of winter.  Some are diagnosed with something called Seasonal Affective Disorder – and some of those are successfully treated with light therapy.

There’s been some compelling research these last few years into the health impacts from our portable electronic devices (smartphones, e-readers, tablet computers) and LCD displays (computers and televisions).  One of the things researchers have discovered is that all of these devices emit much higher levels of white and blue light, and that high levels of white and blue light interrupt production of melatonin – which normally is triggered by red, yellow, and orange light we experience in late afternoon and evening.  Melatonin makes us get sleepy, and is critical to maintenance of our circadian rhythm – our internal clock that governs sleeping and waking.

I tend to think of winter as having lots of darkness and being more conducive to sleep; but, in fact, sunlight coming through the atmosphere in winter (late October to early March in North America) contains a great deal more white and blue light.  Ever noticed how winter sunlight seems crisper and brighter?  Add some reflective snow or ice and it can seem extremely bright.

Evidently, we compound the problem dramatically when we use all these gizmos with LCD, LED and more modern sources of light.  If you put on a pair of good polarized sunglasses, or those goofy orange “blue blockers”, you’ll notice the screen of your smartphone or ipad becomes almost invisible!

Here are some tricks I’ve discovered that help insure better sleep in winter (late December through mid February is when most people seem to report the most difficulty):

Try to (at least temporarily) replace flourescent and LED lighting with old-fashioned clear incandescent lights which emit less blue light and more warm yellow light.  Some people report they “feel warmer” with incandescent lighting in winter.

Start wearing a good pair of sunglasses when outdoors after mid October.  Your sleep probably hasn’t been interrupted by that early in the season but your eyes and body are already sensing the change in light.  By the time sleep is impacted in the dead of winter, your circadian rhythm has already (mal) adjusted to the higher white and blue light; so keep those shades handy and start wearing them before Halloween!

Install software to adjust the light emitted from your computer, tablet, or smartphone screens.  F.Lux is free for Windows and Mac computers (and inexpensive for other devices).  You may find other similar programs with some searching.

You can adjust your LCD flatscreen TV, too, so that more red and yellow light is emitted, and less blue light.

Unplug all those LED nightlights you might have around the house.  You can still get nightlights with low-wattage incandescent bulbs.

Try to reduce usage of your smartphone/tablet/computer devices late in the day and, by all means, don’t use them in the bedroom where you sleep!  For a good example of light that’s severely detrimental to sleep, go in a dark room and switch your laptop computer screen to “blank” or “black”.  Let your eyes adjust to the darkness and you’ll begin to notice an eerie blue shade of light in the room.  Lots of people who report sleep troubles also report they can see very well in this range of light!  Their eyes are more receptive of the kinds of light that clobber sleep!

Finally, give yourself a “longer runway” for going to sleep.  Are those primetime shows (2-3 hours after sundown) really that important??  Remember that, even though you don’t fall asleep as quickly as you might in summer, being in a dark room and restful state give your system its best chance for sleep.

Most importantly, sleep difficulty can be a component of severe anxiety or depression.  These are clinical conditions with well-understood clinical solutions so see a doctor or mental health worker right away!

More information about light and sleep physiology:

In Eyes, a Clock Calibrated by Wavelengths of Light
Light-emitting portable devices and sleep, National Academy of Science