Green light also alters sleep, television before bed still bad

Sleep experts warn the bright light produced by televisions, computers and iPads can meddle with sleep. There’s a line of products made to counter that effect by blocking out blue light wavelengths, which can reset the body’s circadian clock. Online you can purchase special sunglasses and screen filters, but there’s no guarantee the products will work as advertised and prevent insomnia.

There’s new evidence that its not just blue wavelength light that alters the body’s circadian clock. Researchers at the Brigham and Women’s Hospital in Boston found the green light produced from those same sources has a similar effect.

More than a decade ago, scientists discovered there are special cells in the eye that contain the blue light-absorbing pigment melanopsin. When the eye detects blue light, it delays the body from secreting melatonin.

The authors of the new study wanted to see if the eye’s rods and cones, which respond to green light wavelengths, also contributed to the body’s circadian adjustment.

The researchers exposed a group of volunteers separately to blue and green light, both for several durations and intensities. The experiment happened in the evening, before the body naturally secretes melatonin. Scientists measured the subjects’ melatonin response in each condition.

At low intensity, there was very little difference in the body’s reaction to blue and green light wavelengths. However, blue light produced a greater effect over time and at higher intensities.

The authors suggest there’s room to improve light therapy for sleep disorders based on these findings. The treatment may be more effective if the light devices combined blue and green light.

The study may have potentially substantial implications for the field of sleep research.

AASM President Clete Kushida told USA Today “(the finding) sort of goes against what was believed before.”

He said researchers should explore the possibility that the full spectrum of light may affect the body clock.

For our readers who aren’t scientists, the study reinforces the notion that evening use of electronic screens can hinder sleep, and special sunglasses won’t help. We recommend shutting off the television or other bright electronic devices an hour before bedtime and picking up a book, or better yet, an e-reader.