Nov. 6, 2024 – This past weekend, most Americans turned their clocks back an hour, marking the end of daylight saving time and signaling the seasonal transition to shorter days and longer nights. Shorter days means less light exposure, disrupting your circadian rhythm – the internal body clock that controls when you feel sleepy or alert, as well as your metabolism and the release of hormones.
As more and more research reveals the critical role of circadian rhythms in health and disease, interest in circadian medicine has been growing. Disruptions in the internal clock have been linked to a higher risk for heart disease, diabetes, obesity, depression, dementia, and more.
Health tech companies are starting to catch on.
Recently, there’s been a rise in wearable gadgets, apps, and sensors claiming to help realign the body’s circadian rhythm, improving sleep, alertness, and mood. Most leverage the effects of light exposure – the factor researchers say has the strongest influence on circadian rhythms.
But do these devices work? Here’s what to know.
How Light and Darkness Impact Your Health
Our circadian rhythm is controlled by a master clock called the suprachiasmatic nucleus (SCN), located in the center of the brain about 2 centimeters behind the eyes, where the optic nerves cross.
Light exposure helps the SCN synchronize to the sun’s oscillations and release the hormone cortisol, which promotes alertness and wakefulness during the day, said Mariana Figueiro, PhD, director of the Light and Health Research Center at Mount Sinai in New York City.
At night, the SCN sends a sleep signal, suppressing cortisol and releasing the sleep hormone melatonin. When it’s functioning correctly, this system helps the body remain asleep until morning. At the same time, “sleep pressure” – the body’s biological urge to stay awake – builds during the day and diminishes at night.
Unfortunately, our brightly lit modern world – illuminated by streetlamps, neon signs, and backlit electronic devices – isn’t great for regulating this system. Add in longer working hours, night shifts, and the ability to easily travel across time zones, and we’ve found plenty of ways to challenge natural biology.
With any “deviation, the body’s rhythms don’t move at the same pace as the environment and start to dissociate from one another,” said Thomas Kantermann, PhD, professor of health psychology at FOM University of Applied Sciences in Bochum, Germany. Other examples include turning the clocks back or forward and the seasonal changes in light as the earth tilts away from or toward the sun.
The result is an increased risk for sleep disorders plus a host of other health challenges, including mood disorders, cancer, diabetes, obesity, and heart attacks.
Can Technology Help?
Bridget Pilloud, a writer based in Washington State and Arizona, has struggled with seasonal affective disorder (SAD), a low-grade seasonal depression, for years.
“It starts as soon as the light starts to change, in late August,” she said. “Everyone else feels like it’s still summer, but I feel the light changing and I slow down. It takes me longer to get ready in the morning and a lot more effort to get things done.”
Pilloud said that between October and December, her condition becomes progressively worse and systemic.
After trying a host of treatments – antidepressants, vitamin D, light box therapy, and exercise – Pilloud finally turned to Ayo light therapy glasses. They work by delivering blue and red light at customized intensities.
“I started using it this past September, and right away, I felt normal and didn’t have depression again until mid-October,” she said. “So I did a bit more research and started using them for a longer session, and I felt normal again in four to five days.”
Ayo is not the only device competing in the circadian health space. Others include sleep masks (Lumos Smart Sleep Mask and Bia Smart Mask), glasses (Luminette light therapy glasses), and wearable sensors that measure changes in light (like the MiEye sensor, which is available only to researchers). Additionally, apps like Timeshifter and myCircadianClock provide personalized prompts to optimize light exposure and sleep.
Though Pilloud’s experience sounds promising, research shows mixed results on how effective these tools are.
One small clinical trial examined the Ayo glasses in patients with fatigue. “Our findings showed that for some people, the glasses do work,” said study author Mark Butler, PhD, a psychologist and investigator at the Institute of Health System Science at the Feinstein Institutes for Medical Research at Northwell Health in Manhasset, New York. “And in general, there’s a small but significant effect. For others, it didn’t do anything.”
One important limitation of light therapy glasses, said Figueiro, is design and positioning. “If the glasses are not worn in a certain position on the face, they won’t deliver the amount of needed light,” she said.
Timing of light exposure also matters, and so does intensity – the more intense the light, the more likely the response will be, said Kantermann, who has advised AYO’s founders pro bono. Researchers have also been looking into “light temperature," or hues. Cooler hues like blue are believed to suppress melatonin and improve alertness, while warmer hues – reds, oranges, and yellows – do the opposite.
Figueiro and her team are working with a business to commercialize a light meter – a device that measures the amount of light in a given environment and produces feedback for a personalized “light recipe” (how the light can be adjusted or best optimized to be in accord with one’s circadian rhythm). They’ve also been working on indoor lighting solutions – for example, using different lighting intensities or exposures in nursing homes for residents with Alzheimer’s and Parkinson’s. She noted that these solutions led to improvements in sleep, mood, behavior, and cognitive function.
Another consideration is behavior change. “The trickiest thing is that you have to do [the therapy] every day,” said Kantermann, “It has to be a routine so your system becomes stable and synchronizes.”
He believes that to be effective, the intervention needs to be administered passively – meaning the system monitors progress and adjusts automatically “without the person having to do anything,” he said.
“We’re using a series of light flashes that are administered when someone is sleeping in a specific sequence and at different times in the night, but they don’t interfere with sleep or wake the user,” he said. “What it does is basically synchronizes your circadian clock without requiring you to change your behavior.”
Then there’s the price. The Ayo and Luminette glasses are about $200, and sleep masks can cost $300 or more.
For now, the best option for most people is the simplest: “When the sun rises, go outdoors [for] 20 minutes or a half hour or more, depending on your schedule,” said Kantermann.
“Our clocks are looking for bright days and dark nights,” Figueiro said. “Take advantage of as many opportunities you have during the day to get as much light as you can.”
