Nav: Home

Why screen time can disrupt sleep

November 27, 2018

LA JOLLA--(November 27, 2018) For most, the time spent staring at screens--on computers, phones, iPads--constitutes many hours and can often disrupt sleep. Now, Salk Institute researchers have pinpointed how certain cells in the eye process ambient light and reset our internal clocks, the daily cycles of physiological processes known as the circadian rhythm. When these cells are exposed to artificial light late into the night, our internal clocks can get confused, resulting in a host of health issues.

The results, published November 27, 2018, in Cell Reports, may help lead to new treatments for migraines, insomnia, jet lag and circadian rhythm disorders, which have been tied to cognitive dysfunction, cancer, obesity, insulin resistance, metabolic syndrome and more.

"We are continuously exposed to artificial light, whether from screen time, spending the day indoors or staying awake late at night," says Salk Professor Satchin Panda, senior author of the study. "This lifestyle causes disruptions to our circadian rhythms and has deleterious consequences on health."

The backs of our eyes contain a sensory membrane called the retina, whose innermost layer contains a tiny subpopulation of light-sensitive cells that operate like pixels in a digital camera. When these cells are exposed to ongoing light, a protein called melanopsin continually regenerates within them, signaling levels of ambient light directly to the brain to regulate consciousness, sleep and alertness. Melanopsin plays a pivotal role in synchronizing our internal clock after 10 minutes of illumination and, under bright light, suppresses the hormone melatonin, responsible for regulating sleep.

"Compared to other light-sensing cells in the eye, melanopsin cells respond as long as the light lasts, or even a few seconds longer," says Ludovic Mure, staff scientist and first author of the paper. "That's critical, because our circadian clocks are designed to respond only to prolonged illumination."

In the new work, the Salk researchers used molecular tools to turn on production of melanopsin in retinal cells in mice. They discovered that some of these cells have the ability to sustain light responses when exposed to repeated long pulses of light, while others become desensitized.

Conventional wisdom has held that proteins called arrestins, which stop the activity of certain receptors, should halt cells' photosensitive response within seconds of lights coming on. The researchers were surprised to find that arrestins are in fact necessary for melanopsin to continue responding to prolonged illumination.

In mice lacking either version of the arrestin protein (beta arrestin 1 and beta arrestin 2), the melanopsin-producing retinal cells failed to sustain their sensitivity to light under prolonged illumination. The reason, it turns out, is that arrestin helps melanopsin regenerate in the retinal cells.

"Our study suggests the two arrestins accomplish regeneration of melanopsin in a peculiar way," Panda says. "One arrestin does its conventional job of arresting the response, and the other helps the melanopsin protein reload its retinal light-sensing co-factor. When these two steps are done in quick succession, the cell appears to respond continuously to light."

By better understanding the interactions of melanopsin in the body and how the eyes react to light, Panda hopes to find new targets to counter skewed circadian rhythms due to, for example, artificial illumination. Previously, Panda's research team discovered that chemicals called opsinamides could block melanopsin's activity in mice without affecting their vision, offering a potential therapeutic avenue to address hypersensitivity to light experienced by migraine sufferers. Next, the researchers aim to find ways to influence melanopsin to reset the internal clocks and help with insomnia.
-end-
Other authors include former Salk postdoctoral researcher Megumi Hatori, now at Keio University School of Medicine in Tokyo; Kiersten Ruda and James Demas of St. Olaf College; and Salk former visiting graduate student Giorgia Benegiamo.

This work was supported by the Leona M. and Harry B. Helmsley Charitable Trust, the National Institutes of Health and the Glenn Foundation.

About the Salk Institute for Biological Studies:

Every cure has a starting point. The Salk Institute embodies Jonas Salk's mission to dare to make dreams into reality. Its internationally renowned and award-winning scientists explore the very foundations of life, seeking new understandings in neuroscience, genetics, immunology, plant biology and more. The Institute is an independent nonprofit organization and architectural landmark: small by choice, intimate by nature and fearless in the face of any challenge. Be it cancer or Alzheimer's, aging or diabetes, Salk is where cures begin. Learn more at: salk.edu.

Salk Institute

Related Sleep Articles:

Baby sleeping in same room associated with less sleep, unsafe sleep habits
The American Academy of Pediatrics (AAP) recommends parents keep babies in the same room with them to sleep for the first year to prevent sudden infant death syndrome (SIDS).
Alternating skimpy sleep with sleep marathons hurts attention, creativity in young adults
Skimping on sleep, followed by 'catch-up' days with long snoozes, is tied to worse cognition -- both in attention and creativity -- in young adults, in particular those tackling major projects, Baylor University researchers have found.
Sleep trackers can prompt sleep problems
A researcher and clinician in the sleep disorders program in the Department of Behavioral Sciences at Rush University Medical Center and an associate professor at Rush University, Baron says use of these devices follows a pattern reflected in the title of the Sleep Medicine study: 'Orthosomnia: Are Some Patients Taking the Quantified Self Too Far?'
UW sleep research high-resolution images show how the brain resets during sleep
Striking electron microscope pictures from inside the brains of mice suggest what happens in our own brain every day: Our synapses -- the junctions between nerve cells -- grow strong and large during the stimulation of daytime, then shrink by nearly 20 percent while we sleep, creating room for more growth and learning the next day.
What is good quality sleep? National Sleep Foundation provides guidance
The National Sleep Foundation (NSF) recently released the key indicators of good sleep quality, as established by a panel of experts.
Homeless sleep less, more likely to have insomnia; sleep improvements needed
The homeless sleep less and are more likely to have insomnia and daytime fatigue than people in the general population, findings researchers believe suggest more attention needs to be paid to improving sleep for this vulnerable population, according to a research letter published online by JAMA Internal Medicine.
Losing sleep over discrimination? 'Everyday discrimination' may contribute to sleep problems
People who perceive more discrimination in daily life have higher rates of sleep problems, based on both subjective and objective measures, reports a study in Psychosomatic Medicine: Journal of Biobehavioral Medicine, the official journal of the American Psychosomatic Society.
Mouse mutants with sleep defects may shed light on the mysteries of sleep
The first unbiased genetic screen for sleep defects in mice has yielded two interesting mutants, Sleepy, which sleeps excessively, and Dreamless, which lacks rapid eye movement (REM) sleep.
Brain circuit that drives sleep-wake states, sleep-preparation behavior is identified
Stanford University School of Medicine scientists have identified a brain circuit that's indispensable to the sleep-wake cycle.
Recharge with sleep: Pediatric sleep recommendations promoting optimal health
For the first time, the American Academy of Sleep Medicine has released official consensus recommendations for the amount of sleep needed to promote optimal health in children and teenagers to avoid the health risks of insufficient sleep.

Related Sleep Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".