American scientists find how screen time disrupts sleep

WASHINGTON — American researchers revealed how screen time could disrupt one’s sleep, as some cells in the eye, when exposed to artificial light late into the night, were linked to the confusion of people’s internal clocks.

The study, published on Tuesday in the journal Cell Reports, may help lead to treatments for insomnia, jet lag, and migraines. Those conditions are also tied to cognitive dysfunction, cancer, obesity, and metabolic syndrome.

“We are continuously exposed to artificial light, whether from screen time, spending the day indoors or staying awake late at night,” said Salk Institution professor Satchin Panda, the senior author of the study.

“This lifestyle causes disruptions to our circadian rhythms and has deleterious consequences on health,” Panda said.

The back of one’s eyes contain a sensory membrane called the retina, whose innermost layer contains a tiny population of light-sensitive cells that operate like pixels in a digital camera, according to the study.

When those 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.

The protein plays a pivotal role in synchronizing our internal clock after 10 minutes of illumination and under bright light, it suppresses the hormone melatonin that is responsible for regulating sleep, according to the study.

The Salk researchers used molecular tools to turn on production of melanopsin in retinal cells in mice and they found that some of these cells had the ability to sustain light responses when exposed to repeated long pulses of light, while others become desensitized.

They also found that arrestins, proteins that usually stop the activity of certain receptors, in fact were necessary for melanopsin to continue responding to prolonged illumination.

In mice-lacking arrestin proteins, the retinal cells failed to sustain their sensitivity to light under prolonged illumination.

A better understanding of the interactions of melanopsin and how eyes react to light could lend new targets to counter skewed circadian rhythms due to long screen time.

Panda’s team has discovered that chemicals called opsinamides could block melanopsin’s activity in mice without affecting their vision, offering a potential therapeutic way to address hypersensitivity to light experienced by migraine sufferers.

The researchers plan to find ways to make melanopsin to reset the internal clocks and help with insomnia.