Caution: iPad reading may disrupt your sleep cycle

When it comes to sleeping, the human brain is a finely tuned machine. It is designed to allow us the 8 hours of sleep we need each night, without putting us at risk for attack from predators or missing out on meals. Sometimes, without intending to, we can short circuit these built-in protections and disrupt our own sleep pattens. It is a good reminder that light-emitting devices like the Apple iPad can lead to a worse night's sleep, if misused.

Light-emitting devices, including cellphones and yep, the iPad, tell the brain to stay alert. Because users hold those devices so close to their face, staring directly into the light, the effect is amplified compared with, say, a TV across the room or a bedside lamp, said Frisca Yan-Go, director of the UCLA Sleep Disorders Center in Santa Monica.

Your mileage may vary, as the brain is also a very flexible, adaptable machine. But if you find yourself losing sleep after picking up a Netbook or iPad as a portable bedtime reader, it may be time to rethink your investment. Or switch over to paper for your bedtime story.