Blue light, devices might crimp teens’ zzzs

Young people aren't getting enough sleep, sacrificing quality shut-eye for greater nighttime device use that might only further disrupt normal sleep-wake cycles, and blue light partly could be to blame.

Published in the journal Sleep Medicine, a recent meta-analysis from San Diego State University (SDSU) posited that more adolescents than ever are receiving less than seven hours of sleep nightly, generally regarded as insufficient, while longer daily device use among this age group correlated with less overall sleep.

Analyzing data from the "Monitoring the Future" survey and Youth Risk Behavior Surveillance System—totaling responses from more than 360,000 teenagers—researchers found that 40% of adolescents in 2015 slept less than seven hours nightly. This is more than 58% higher than in 1991 and 17% higher than in 2009, a date when researchers suggest smartphone usage took off.

On top of that, researchers determined adolescents spending more than five hours online daily were 50% more likely to not sleep enough, as compared to peers who spent only an hour online daily.

Study authors note that besides the time spent using devices offsetting sleep, previous research suggests blue light exposure could interfere with the body's natural circadian rhythm.

"Given the importance of sleep for both physical and mental health, both teens and adults should consider whether their smartphone use is interfering with their sleep," says study author Jean Twenge in an SDSU news release. "It's particularly important not to use screen devices right before bed, as they might interfere with falling asleep."

This sleep research appears only days after an unrelated study from a Nova Southeastern University College of Optometry student concluded blue-light-filtering lenses nearly doubled melatonin levels at night, helping promote sleep and reduce awakenings during sleep.

As first reported in Medscape Medical News, student Ryab-Quang Van conducted a randomized, cross-over study to determine the effects of blue light filtering lenses worn after 6 p.m. nightly for one week. Participants wearing those lenses were found to have melatonin levels almost double that of control subjects, and reported less awakenings during sleep. Medscape reports Van intends to continue the study on a larger scale to see if these findings hold.

AOA offers pediatric, blue light resources

Blue light's detrimental effect on sleep centers on melatonin production. Melatonin, a natural hormone that helps regulate the body's circadian rhythm, typically elevates in the evening hours; however, exposure to artificial blue light (short-wavelength, high-energy visible light) at nighttime can trick the eyes into suppressing melatonin in much the same way natural sunlight does. This suppression is believed to correlate with wakefulness and a delayed or poor sleep cycle.

"Exposure to high levels of short-wavelength visible energy (blue light) also has the potential to cause photochemical retinal damage, which is known to occur with direct sun viewing," states the AOA's Comprehensive Pediatric Eye and Vision Examination guideline.

"In addition, the increased evening use of laptops and other broad-spectrum, self-illuminated devices rich in blue light has been suggested to interfere with good sleep hygiene, especially in adolescents."

While prolonged, natural UV exposure from direct sunlight can have long-term consequences on vision, the artificial blue light emitted from digital device screens isn't harsh enough to have this effect. That said, extended device use can cause other problems, such as dry eyes, blurred vision or headaches.

The AOA's Infant & Children's Vision Committee offers resources for helping doctors discuss pediatric blue light exposure with patients and parents, including the "Blue Light Impact in Children" fact sheet. This resource provides not only a background into the blue light debate, but also references for further reading on the subject.

Doctors can access the AOA's evidence-based clinical practice guideline Comprehensive Pediatric Eye and Vision Examination.