A study that came out recently in the Journal of Clinical Sleep Medicine confirmed something slightly obvious but yet vastly underrated: light at night is causing problems with sleep.  

The study used data from the South Korean national health plan to determine how many people were using prescription sleep medication and then combined this data with a bunch of satellite imaging data to determine the light pollution levels.

The study broke up the amount of outdoor light at night into four quartiles. The results showed that there was a statistically significant increase in sleep drug use in each of the four quartiles. In other words, those people who were exposed to light in the 50 - 75th percentile range were taking more sleep drugs than those in the 25 - 50th quartile range of light.

Each quartile of increased light at night = more prescription sleeping pills

There were a couple of things in the findings that surprised me:

1) The study group size was over 52,000 people, and almost 23% of that population was using prescription sleep medications. In comparison, only about 4% of the US population is on prescription sleep drugs. I don't know if there are more people in S. Korea having problems sleeping or if people in the US are buying OTC sleeping meds instead of prescription drugs.

2) The researchers adjusted for a bunch of variables such as income, age, sex, residential area, BMI, smoking, alcohol, psychiatric diseases, etc. And adjusting for all the variables didn't make that much of a difference. The prescription sleep drug use was still significantly greater across each quartile of amount of light at night.

3) The government of any country with socialized health care has a lot of data on its people...  Being able to match up prescription usage to residential areas mapped to satellite imaging to determine light intensity at the street level at night - makes for interesting scientific studies, when the data is used for good.

Science behind light at night causing insomnia:

Light at night in the blue wavelengths shuts off melatonin production and signals to the body that it is daytime. Thus the recommendation to either wear blue blocking glasses at night or shut off your electronics and bright overhead lights.

But that doesn't really explain why low levels of light  - dim light coming through your windows from streetlights and your neighbor's floodlight over their garage door (turn it off!) - cause problems with sleep. When you are sleeping, your eyes are closed and you can't see the light, right?

It turns out that your eyelids don't fully block out the dim light from the streets.  There have been several studies done showing that light delivered through the eyelids can suppress melatonin levels. (study)(study) Studies on breast cancer risk from light at night show a strong correlation between areas with greater than 16 lux. (study) Breast cancer risk is tied in with melatonin levels. Another study found that sleeping with the shutters closed (in Israel) decreased the risk of breast cancer. (study)  

What to do about light at night? #SleepInTheDark

The solutions here are simple:

  • block out the blue wavelengths in your home in the evening
  • sleep in the dark

Buy some room darkening curtains and use them. If you already have fancy curtains in your room that don't do much for the light, you can always double hang some blackout curtains behind your pretty curtains, or you can put up some roller shades behind your regular curtains.

Amazon has blackout panels for less than $9 each. Still too much money? Try Goodwill or another thrift store.

Or put up blackout shades behind the curtains you already have.