The Sun is Critical to Your Sleep

by Stephen Mills on February 23, 2009

Sunny Sailboat

If you want to have more energy in the day and sleep better at night, you need to get plenty of sunlight and get it at the right time of the day.  Our biology developed in the absence of indoor lighting.  Our ancestors woke up with and were active in the sunlight.  They slept in the dark.  The cycle of sunlight and darkness regulates hormonal systems in our body and is very important in maintaining a healthy circadian rhythm.  Sunlight + Activity = Awake.  Darkness + Inactivity = sleep.  Our modern technological society and culture have damaged this cycle for most people.  Artificial lighting and indoor living have dimmed the day and brightened the night.  Instead of a sharply rising and falling cycle, it is flattened out to varying degrees for most people.  As a result they are sleepy in the daytime and can’t sleep well at night.

Your internal circadian clock needs to be reset daily and the best way to do that it to get early morning sunlight.  An hour of sunlight and activity before 8:30 AM seems to be the best but any amount at any time in the morning is better than nothing.  Early morning walks are an ideal way to do this.  I can’t get that much activity or sunlight in each day, but I try to get 20-30 minutes of outdoor walking before 10:00 AM and when possible I get it before 8:30 AM.  The more problems you have with sleep the more important this is, but it will benefit almost everyone.

To understand the magnitude of differences between the indoor and outdoor light intensities which are measured in LUX, consider the following:

Typical family living room = 50 LUX

Typical office = 300 LUX

Overcast daylight = 1,000 LUX

Full Sunlight = 10,000 LUX

Looking at the Sun = 100,000 LUX

Going outside in the Sun, which is the environment in which our biology developed is 200 times brighter than being in your living room and even 20 or 30 times brighter than being in your office.  While dim indoor lighting will disturb your sleep cycle it is not bright enough to reset your clock correctly.  Thus being indoors with lights during the day is bad for you and so is being indoors at night with lights.

What Should I do?

  1. Get at least 20 minutes of morning sunshine or at least 30 minutes overcast (cloudy) daylight.  If you find yourself getting sleepy in the evening then also get some afternoon sunshine.  Do this by walking and you’ll get some quality exercise at the same time.
  2. More light is better.  Brighter indoor lights are better than dim indoor lights and full sun is better than overcast conditions.  Facing towards the sun is better than away, but of course do not look directly at it.  Light boxes are better than indoor lights, but outdoor light is better than light boxes.  Sun coming through a window is better than indoor lighting.  Being in the sunshine coming into a room is better than being in the shade in the same room.
  3. The light must enter your eyes.  The circadian rhythm is not impacted by the light hitting your skin.  So do not wear sunglasses or you will be defeating the purpose of the light exposure.
  4. Earlier in the day is better than later in the day.  Morning is better than afternoon and afternoon is better than evening.

I personally have found morning walks in the sun have dramatically helped my sleep, improved my mood, and provided some much needed exercise.

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{ 5 comments… read them below or add one }

Michael Bungartz February 25, 2009 at 8:49 am

Stephen…Great article on the sun effect on our sleep cycles. Quality stuff, well done sir!


Stephen - Rat Race Trap February 25, 2009 at 12:38 pm

Thank you Micheal! I’m glad you enjoyed it.


Clement Yeung February 28, 2009 at 10:32 pm

You know, I was just thinking about how I miss sunshine today!

Here in the UK, we have sunlight deficiency. Also, being a blogger won’t help as you’re always stuck behind the PC in the darkened room.

So, being a blogger in the UK really will take its toll on your biology, right?!



Stephen - Rat Race Trap February 28, 2009 at 11:15 pm

Clement, you are doomed to a life of being tired. LOL.


Cynthia December 28, 2010 at 12:49 pm

hey, i live in BARBADOS, & I really njoyed the article re benefits of the morning sunshine!!!
i would like 2 kno where they got the ides re cancer from sunlight??

we all living here will be doomed!!!


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