What disturbs sleep for teens is ...

... gadget lights! Who would have guessed? And yes, sarcasm. Original article from the Post is here.

The pervasive glow of electronic devices may be an impediment to a good night’s sleep. That’s particularly noticeable now, when families are adjusting to early wake-up times for school. Teenagers can find it especially hard to get started in the morning. For nocturnal animals, it spurs activity. For daytime species such as humans, melatonin signals that it’s time to sleep.

As lamps switch off in teens’ bedrooms across America, the lights from their computer screens, smartphones and tablets often stay on throughout the night. These devices emit light of all colors, but it’s the blues in particular that pose a danger to sleep. Blue light is especially good at preventing the release of melatonin, a hormone associated with nighttime.
 

Ordinarily, the pineal gland, a pea-size organ in the brain, begins to release melatonin a couple of hours before your regular bedtime. The hormone is no sleeping pill, but it does reduce alertness and make sleep more inviting.

However, light — particularly of the blue variety — can keep the pineal gland from releasing melatonin, thus warding off sleepiness. You don’t have to be staring directly at a television or computer screen: If enough blue light hits the eye, the gland can stop releasing melatonin. So easing into bed with a tablet or a laptop makes it harder to take a long snooze, especially for sleep-deprived teenagers who are more vulnerable to the effects of light than adults.

During adolescence, the circadian rhythm shifts, and teens feel more awake later at night. Switching on a TV show or video game just before bedtime will push off sleepiness even later even if they have to be up by 6 a.m. to get to school on time.

The result? Drowsy students struggling to stay awake, despite the caffeinated drinks many kids now consume.

“Teenagers have all the same risks of light exposure, but they are systematically sleep-deprived because of how society works against their natural clocks,” said sleep researcher Steven Lockley of Harvard Medical School. 

Based on what parents reported, sleep quality was better among children age 6 to 17 who always turned their devices off: 45 percent of them were described as having excellent sleep quality vs. 25 percent of those who sometimes left devices on.

“It is known that teenagers have trouble falling asleep early, and every teenager goes through that,” said light researcher Mariana Figueiro of the Rensselaer Polytechnic Institute in Troy, N.Y.

Figueiro investigates how light affects human health, and her recent research focused on finding out which electronics emit blue light intense enough to affect sleep. When comparing melatonin levels of adults and teenagers looking at computer screens, she was astonished by the younger group’s light sensitivity. Even when exposed to just one-tenth as much light as adults were, the teens actually suppressed more melatonin than the older people.

In another experiment, she had adults use iPads at full brightness for two hours and measured their melatonin levels with saliva samples. One hour of use didn’t significantly curtail melatonin release, but two hours’ did.

So although teenagers may be particularly susceptible, we all should be aware that artificial light can affect our circadian rhythms.

“The premise to remember is [that] all light after dusk is unnatural,” Lockley said. “All of us push our sleep later than we actually would if we didn’t have electric light.”

A study from 2013 found that people who spent a week camping in the Rocky Mountains, exposed to only natural light and no electronic devices, had their circadian clocks synchronized with the rise and fall of the sun. Although there were only eight campers, they all reacted in the same way, whether they considered themselves early birds or night owls. 

So light serves as a cue, but how? It has long been known that the retina contains two types of photoreceptors, or light sensors: rods and cones. The cones allow us to see colors, while the ultra-sensitive rods are used for night vision, motion detection and peripheral vision. But surprisingly, neither of them is the body’s primary tool for detecting light and darkness and synchronizing our circadian clocks.  

“Sleep is important for learning, memory, brain development, health,” Lockley said. “We’re systematically sleep-depriving kids when their brains are still developing, and you couldn’t design a worse system for learning.” Many Americans may believe early risers are more successful and that people can learn to live on little sleep, Lockley said, but that notion is neither true nor healthy. “There’s no training people to live without sleep,” Lockley said. “It’s like trying to train people to live without food.”