Seeing Blue

Rosie Blau (as our German readers chuckle) looks at how light affects our health:

In the morning, high concentrations of blue occur naturally; by dusk we are left mostly with green and red. The blue light has the greatest impact on our circadian system, telling the brain that it’s morning and time to be alert, and setting our clock for the day. That is important because we sleep soundly, and our brain and body function better, when the internal signals of the body clock are in sync with external cues of day and night.

The problem is that artificial light does not replicate the colours of the natural world. Much electric light has high intensities of blue, so it deceives our brains into thinking that it’s daytime even when it isn’t. Just ten minutes of regular electric light can make some changes to our internal clock. “We evolved to be blue-sensitive, we need it,” says [professor Satchin] Panda. But many of us get an awful lot of it, particularly in the evening: when we get home we spotlight the kitchen so we can make the dinner, and then plug into our laptops, tablets or smartphones, which beam blue light into our eyes at close range. So we … lessen the contrast between light and dark that our circadian system relies on to work well. All of which makes us more prone to insomnia or disturbed sleep in some way.

But artificial light isn’t all bad:

Teenagers the world over should be cheering on the work of Mariana Figueiro, an expert on light and health at Rensselaer Polytechnic Institute in upstate New York. In 2012 she found that when a group of young adults used an iPad for two hours before bedtime, they suppressed their production of melatonin, a sleep-promoting hormone. The media focused on the obvious conclusion: that using such backlit devices ruins our sleep.

But Figueiro draws another inference too. Because they blast us with blue light, these same backlit items could act as light therapy by day to help invigorate us and reset our clock. She may be the first person to prescribe an hour playing “Angry Birds” each morning as a solution to our ills.

(Photo by Gisela Giardino)