E-readers may make it particularly hard to get a good night's sleep, according to research out this week.
A study that followed every nightly twitch, turn and snore of 12 volunteers for a couple weeks found that those who read from an iPad before hitting the sack had a harder time falling asleep, spent less time in a crucial phase of sleep, and were less alert the next day.
This is cause for concern because sleep disruptions may be associated with a variety of health problems, according to the study's leader, Anne-Marie Chang, who studies sleep and circadian rhythms at the Brigham & Women's Hospital in Boston. "Sleep deficiency is associated with negative consequences for health," including obesity, diabetes, cardiovascular disease, Chang says.
Previous research has indicated that exposure to certain types of light seems to disrupt sleep more than others, Chang says. Devices that emit shorter-wavelength, blue light might be especially problematic, she and her team suspected, because it has the greatest effect on the hormone melatonin, which regulates sleep.
"We knew that light in the evening affects circadian rhythms and affects sleep and alertness," Chang says. "But we wanted to test if light from light-emitting devices, such as e-readers, which were gaining in popularity, would have the same effect if people were using them to read before bedtime."
So the researchers asked 12 healthy young people to spend a couple of weeks in a sleep lab. For five nights, they read what they considered to be relaxing material on an iPad for four hours before going to sleep. For another five nights, they read the same kind of material from books made of paper.
In the study published in this week's issue of the Proceedings of the National Academy of Sciences, the researchers found that on the nights participants read from iPads, it took longer for them to fall asleep and they spent less time in an important phase of slumber known as rapid eye movement (REM) sleep.
"They also reported feeling less sleepy in the evening but more sleepy the following morning," Chang says.
The team also discovered that the light from the iPad was suppressing and delaying the production of melatonin.
Based on the findings and others, Chang recommends that if people want to read before bed, they should consider devices that don't emit light — or just pull out an old-fashioned paper book.
ROBERT SIEGEL, HOST:
There are some good reading suggestions there. But you should think carefully about when to read them and what you read them on. New research says that combination matters. NPR's Rob Stein reports.
ROB STEIN, BYLINE: Lots of people like to read in bed before going to sleep. And more and more people these days are reading tablets, laptops and other devices. So Anne-Marie Chang at the Brigham & Women's Hospital in Boston and her colleagues decided to test whether doing that affects someone's sleep. It's been known for a long time that being exposed to certain kinds of light at night could disrupt sleep.
ANNE-MARIE CHANG: But we wanted to test if light from light-emitting devices, such as e-readers, which were gaining in popularity, would have this same effect if you people were using them to read before bedtime.
STEIN: So the researchers asked 12 volunteers to live in the lab for a couple of weeks. For five nights they read what they considered to be relaxing material on an iPad for four hours before going to sleep. For another five nights, they read the same kind of stuff from an old-fashioned book. The researchers reported what they found in the proceedings of the National Academy of Sciences.
CHANG: We found that when study participants were reading on the iPad, it took longer for them to fall asleep following. And they had shorter duration of REM sleep, which is a particular stage of sleep. They also reported feeling less sleepy in the evening, but more sleepy the following morning.
STEIN: The researchers also discovered that the kind of light emitted from the iPad and other electronic devices was messing up a really important hormone.
CHANG: They had decreased levels of melatonin, which is the sleep-promoting hormone that normally rises in the evening and peaks at night.
STEIN: Chang says all this is a big worry because other studies have suggested messed up sleep patterns and melatonin levels may increase the risk for some serious health problems.
CHANG: For example, obesity, diabetes, cardiovascular disease, certain cancers.
STEIN: So Chang recommends that if people want to read before bed, they should consider devices that don't emit light or just pull out an old-fashioned paper book. Rob Stein, NPR News. Transcript provided by NPR, Copyright NPR.