Most people who own iPhones use them as their alarm clock — making it all too easy to check email one last time before falling asleep and hard to ever feel unplugged from work and social networks.
Several years ago my boss passed out from exhaustion after staying up late to catch up on work. She banged her head on the way down and ended up with five stitches — and became what she calls a "sleep evangelist." Now she leaves her phone charging in another room when she goes to bed and encourages friends to do the same.
"I sent all my friends the same Christmas gift — a Pottery Barn alarm clock — so they could stop using the excuse that they needed their very tempting iPhone by their bed to wake them up in the morning," she said.
If your phone wakes you up in the morning, it may also be keeping you up at night. A 2008 study funded by major mobile phone makers themselves showed that people exposed to mobile radiation took longer to fall asleep and spent less time in deep sleep.
"The study indicates that during laboratory exposure to 884 MHz wireless signals components of sleep believed to be important for recovery from daily wear and tear are adversely affected," the study concluded.
And that's just a physical symptom of sleeping near the phone — "sham" exposure to a phone without radiation failed to produce the same effect. The itch to check in at all hours of the night or wake up to the sound of a text message disrupts our sleep, too.
A quarter of young people feel like they must be available by phone around the clock, according to a Swedish study that linked heavy cell phone use to sleeping problems, stress and depression. Unreturned messages carry more guilt when the technology to address them lies at our fingertips. Some teens even return text messages while they are asleep.
Most of us choose not to set limits on our nighttime availability. Nearly three-quarters of people from the age of 18 to 44 sleep with their phones within reach, according to a 2012 Time/Qualcomm poll. That number falls off slightly in middle age, but only in people 65 and older is leaving the phone in another room as common as sleeping right next it.