November 18, 2012
Bright Light At Night Elevates Stress Hormone

We've created unnatural environments that we are not evolutionarily adapted to. This causes us many problems including obesity, metabolic syndrome, and assorted addictions. Another item on the list: blue-shifted bright lights at night might be boosting depression, impairing learning, and increasing stress hormones in the blood.

For most of history, humans rose with the sun and slept when it set. Enter Thomas Edison, and with a flick of a switch, night became day, enabling us to work, play and post cat and kid photos on Facebook into the wee hours.

According to a new study of mice led by a Johns Hopkins biologist, however, this typical 21st- century scenario may come at a serious cost: When people routinely burn the midnight oil, they risk suffering depression and learning issues, and not only because of lack of sleep. The culprit could also be exposure to bright light at night from lamps, computers and even iPads.

"Basically, what we found is that chronic exposure to bright light -- even the kind of light you experience in your own living room at home or in the workplace at night if you are a shift worker -- elevates levels of a certain stress hormone in the body, which results in depression and lowers cognitive function," said Samer Hattar, a biology professor in the Johns Hopkins University's Krieger School of Arts and Sciences.

Of course, we might not be like mice in this regard. But the applicability of these results to humans seems very plausible.

Dr. Hattar says when we read at night we should use red-shifted light, not blue-shifted light.

Pay attention to Kelvin numbers when buying bulbs for evening use. Got a room you read in? Go for 2700K at most. I just checked a lot of light bulbs I've got in a closet and most do not have Kelvin numbers. Though some are at 2700K. Looking at an online light bulb site it appears CFL bulbs below 2700K are rare. But if you look for high pressure sodium bulbs you can find them in the 1900k to 2200K range.

Dr. Hattar also says go for less bright bulbs in the evening.

"I'm not saying we have to sit in complete darkness at night, but I do recommend that we should switch on fewer lamps, and stick to less-intense light bulbs: Basically, only use what you need to see. That won't likely be enough to activate those ipRGCs that affect mood," he advises.

What would be handy: A way to record 2 color settings on a PC and then shift between them depending on what you are doing. Go to red/black only for evening text reading.

Share |      Randall Parker, 2012 November 18 05:26 PM 

William Sullivan said at November 18, 2012 5:42 PM:

Flux helps regulate the light from computers -

adam said at November 18, 2012 6:12 PM:

f.lux is great. If you're on linux, I recommend redshift:

I use redshift on all my computers. I just wish I had it for my phone.

Placebo said at November 20, 2012 11:22 AM:

And yet the incandescent street lights in my neighborhood are being replaced with white-blue LED. Is the cost savings worth the stress?

Brett Bellmore said at November 24, 2012 7:01 AM:

One of the reasons I recently unplugged my alarm clock; The light from it was interrupting my sleep. Now I just need to deal with the glare from the smoke detector.

Why does every electronic device in the house have to be lit up, even when supposedly "off"? You can walk from one end of my home to the other at midnight by the LED displays of all the appliances. My wife's tablet has a charging light on it that actually *pulses* when it's plugged in and turned off. What genius thought that up?

If I ever build another house, it's going to have a sleeping chamber off the bedroom, with no windows, and an "airlock" to block light transmission. Best sleep I ever got was when I lived in the basement without a window.

libfree said at November 24, 2012 9:00 AM:

Wifi lights seem be the answer to this. They can be tuned automatically at different times of the day.

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