News
It’s True. It’s Getting Harder to Get a Good Night’s Sleep

It’s True. It’s Getting Harder to Get a Good Night’s Sleep

March 1, 2023

By Shantal Riley

Neuroscientist Orie Shafer explains why modern living keeps us up at night and how we can get some decent shuteye.

A woman's hand is trying to stop an alarm clock in the morning

Credit: Getty Images

Sleep plays an essential role in maintaining optimal physical and mental health. It allows the brain and body to reenergize, restore vital functions, and reset our internal body clocks.

Orie Shafer

Our sleep is regulated by circadian rhythms, the physiological changes that follow the 24-hour light cycle. But, more and more, researchers find that this natural process is being interrupted by modern life.

“The modern light environment acting on our circadian rhythms is chronically sleep-depriving a lot of people and creating ‘social jet lag,’” said Professor Orie Shafer (Biology, Cognitive Neuroscience), who is part of the Neuroscience Initiative at the Advanced Science Research Center at the Graduate Center.

And, thanks to modern lifestyles — lit by blue light from computer screens, cell phones, TVs, and other devices — this disruption of sleep patterns is having a negative impact on our health, says Shafer.

Learn More About the Ph.D. Program in Biology

One Clock Rules Them All

Circadian rhythms are largely guided by natural light and darkness, and they affect the vast majority of organisms on the planet. In humans, they guide sleep-wake cycles, digestion, and changes in body temperature. They induce hibernation in animals, and they drive the flowering cycles of plants.

“They can be behavioral, hormonal, or when genes are most highly expressed … almost any aspect of biology that changes predictably every single day, in accordance with the daily rotation of the Earth,” said Shafer, whose research looks at how circadian rhythms function in the brain of the common fruit fly, Drosophila melanogaster.

Typically, neurons in the timekeeping networks of the fly brain communicate through chemical synapses. But, in 2020, Shafer co-authored a study, in Current Biology, that found these neurons appeared to communicate via broadcast signals. “Instead of tapping on someone’s shoulder, it’s like sending out a radio signal,” Shafer said. “There's very good evidence that something very much like this is going in the mammalian brain.”

Learn More About the M.S. Program in Cognitive Neuroscience

In a new preprint study, Shafer looks at how prolonged natural light affects the circadian rhythms of Drosophila, which shares similar time-keeping neurons with humans. The findings show how the timing and quantity of light exposure can impact the fly’s circadian rhythms.

Yet, even in the absence of daylight, humans have circadian clock cycles that run about 24 hours and 15 minutes each day, Shafer said. But it’s daylight that synchronizes, or “entrains” clock cycles to the 24-hour day.

In fact, the word “circadian” comes from the Latin term “circa diem,” meaning about a day. “The circadian clock, by definition, is precise but inaccurate,” Shafer explained. “It's endogenous, meaning that it persists without any time cues from the environment. It runs very reliably, but it runs at a speed that's either a little fast or a little slow, relative to the 24-hour day.”

There are millions of these clocks found inside the human body, Shafer said. “Circadian clocks are molecular clocks,” said the professor, noting the 2017 Nobel Prize in Physiology or Medicine was awarded to scientists who study how these cellular clocks work.

They’re governed by a master clock, located in the hypothalamus, and a group of nerve cells called the suprachiasmatic nucleus, made up of about 20,000 neurons. “That's the conductor that keeps all of the clocks in the body ticking at the right speed and at the right time,” Shafer said.

A Case of Social Jetlag

This process ran, well, like clockwork, powered by neurons that have done the job for millennia. But a problem arose when, suddenly — relative to our time as a species living on Earth — society imposed drastic changes on our daily work schedules.

It was well into the 20^th century before most Americans even had electricity, Shafer explained. “Before electric light, we were outside much more,” he said. “Our light source was the sun, and maybe a candle or a fire for a couple of hours at night. We had extremely bright days, extremely dark nights, and we oscillated between those two environments with clock-like regularity.”

Fast forward to the present: We spend less and less time outside and the light we do get is not the same as the bright sun. “The light that we get under these fluorescent or LED lights is several log units lower than we would get outside, even during a cloudy day,” Shafer said.

Enter screen-lit computers, used at all hours of the night, and outdoor lighting to confuse our clocks further. “We're staring at screens,” said the professor. “We have cheap electric light. Some people never actually experience enough darkness to see starlight anymore.”

Our private time and work schedules don’t always line up with the rise and setting of the sun. Regardless, he said, daylight is still the most important cue to synchronize the primary circadian clock in humans, whose only clock-setting light source is the retina.

“When we track human sleep, the vast majority of human beings now show an interesting pattern where, for five days during the week, we're getting very little sleep,” Shafer said. “Then on the weekends, when we're free to do whatever we want, sleep not only shifts by several hours, but it's much longer because we're making up for the sleep that we lost throughout the work week. So, there's this five on, two off pattern.”

Chronobiologists refer to this phenomenon as “social jetlag.” It’s created unstable sleep cycles for many of us, said Shafer. “It's the equivalent of getting on a plane, for most people, and traveling two, three or four time zones,” he said.

Modern Life Has a Downside

This all takes a steep toll on human health, said Shafer.

“It's becoming very clear that the stronger the social jet lag you experience, you're more likely to get cancer, you're more likely to be obese, you're more likely to be diabetic, you're more likely to be depressed,” he said. “And you're more likely to abuse both stimulants and depressants.”

Shafer pointed to shift workers who work late at night. “That shift worker's clock is going to try to entrain to the light, but they're going to have to be awake and they're going to have to eat when the clock says to be asleep,” he said. “We think that's one of the reasons why shift workers have higher cancer rates and higher obesity rates.”

The National Sleep Foundation recommends healthy adults get between seven and nine hours of sleep per night. Yet, approximately 35% of American adults report sleeping less than seven hours, according to the CDC.

One might wonder if there’s any hope of ever getting a good night’s sleep.

It depends on your work schedule, Shafer said. “If somebody has to go to sleep at 10 p.m. to get eight hours of sleep before rising for work, but their circadian system is saying, ‘Nope, it's not time to sleep yet,’ it's very hard to get that eight hours of sleep,” he said. “If you can't change your work schedule, you've got to change your clock. And we know that the most potent way to reset your clock is bright sunlight in the morning.”

Natural light in the afternoon can help, too, even on a cloudy day, which Shafer says is “bright light, compared to what you're going to get inside.”

At night, try to avoid bright light emitted by artificial light sources, computers, and other electronic devices. “We want to recreate that high-amplitude rhythm of light and dark, to go back to your roots as a human being and to a strongly entrained clock,” he said.

Shafer recommends sleeping in a cool room and taking a hot shower before bed, which boosts blood flow to the extremities, he said. “This is the same mechanism that the body uses to lower core body temperature in preparation for sleep,” Shafer said. “So, after a shower, your body will be primed to radiate body heat and produce the body cooling that supports good sleep.”

The National Sleep Foundation also recommends avoiding heavy meals two to three hours before bedtime and getting at least 20 minutes of exercise a day.

Visit the Shafer Lab online to learn more about Shafer’s research on circadian rhythms.