Source: http://www.bbc.com/news/health-27286872

Emerging evidence suggests modern technology is now keeping us up later into the night and cutting sleep.

"Light is the most powerful synchroniser of your internal biological clock," Prof Charles Czeisler, from Harvard University, told the BBC Day of the Body Clock.

He said energy efficient light bulbs as well as smartphones, tablets and computers had high levels of light in the blue end of the spectrum which is "right in the sweet spot" for disrupting the body clock.

"Light exposure, especially short wavelength blue-ish light in the evening, will reset our circadian rhythms to a later hour, postponing the release of the sleep-promoting hormone melatonin and making it more difficult for us to get up in the morning.

"It's a big concern that we're being exposed to much more light, sleeping less and, as a consequence, may suffer from many chronic diseases."