Circadian scores are the new sleep scores and a wave of wearables is making them trackable

Sleep scores had their moment. Now circadian scores are the metric wellness culture is fixating on next, a way to translate your body’s 24-hour internal clock into a number you can actually track, adjust and (inevitably) post about. The science underpinning circadian rhythms is well-established, but until recently, measuring them outside a lab was nearly impossible. A new wave of wearables and apps has changed that, promising to align your daily habits with your biology for better sleep, energy and long-term health.

The pitch is straightforward. Your circadian rhythm influences far more than when you feel sleepy. And if you can measure it, the thinking goes, you can optimize it.

What circadian scores actually measure

Circadian rhythms are found in most living organisms and are regulated by light exposure, behavior and a biological clock mechanism made up of clock genes located in cells throughout the body. Circadian scores attempt to quantify how well your daily behaviors, including light exposure, meal timing, activity, and sleep-wake patterns, are keeping that internal clock in sync with the outside world.

According to Harvard research, “Along with metabolism and sleep patterns, the circadian system influences many important functions, including heart rate, blood pressure, body temperature, hormone levels, and urine production. Circadian disruptions and lack of sleep have been associated with serious health problems ranging from cancer to obesity to depression.”

There is a complication. Our innate cycle is not exactly 24 hours, so biological clocks must reset daily to sync with Earth’s rotation. Each person’s light-dark exposure also differs depending on habits and location, which makes timing the biological clock difficult to measure precisely.

Why your circadian rhythm matters beyond sleep

The reach of circadian biology extends well past bedtime. “It turns out that it has been linked to other important outcomes, like cognition and mortality,” Brienne Miner, MD, MHS, assistant professor of medicine (geriatrics) at the Yale School of Medicine, said.

Miner also pointed to how ordinary routines shape the rhythm. “Daylight, exercise, social activity, meal timing, and a regular sleep-wake schedule allow us to keep a normal rhythm. So any changes to these behaviors or lack of these cues from the environment can disrupt the circadian rhythm.”

Even the ordinary act of scrolling in bed can throw the system off. Neuroscientist Jeanne Duffy, MBA, PhD, associate professor of medicine at Harvard Medical School, has found that repeated evening use of light-emitting tablets suppresses melatonin release and shifts the circadian clock later, resulting in a delayed bedtime and reduced alertness the next morning. Adjusting brightness and color tones on devices may help minimize the effect.

“We’re trying to get to the point where we can easily tell the biological time in your body, versus the biological time in mine,” Duffy said, hinting at where personalized circadian science is headed.

Circadian sunmaxxing, the morning-light trend behind the scores

Much of the current circadian score conversation revolves around a habit called “sunmaxxing,” which involves intentionally stepping outside within roughly an hour of waking for 10 to 30 minutes of natural light, longer on cloudy days. The goal is to anchor the body’s rhythms, sharpen daytime alertness and improve sleep timing.

The reasoning holds up in the literature. Morning light is the primary cue for the body’s master clock, and bright early exposure can phase-advance the sleep-wake cycle while modulating cortisol. An NIH-hosted systematic review covering 12 studies and 337 participants found that bright early-day light significantly increases cortisol compared with dim light. Other bright-light studies have measured roughly 20% to 40% higher peak cortisol in the first hour after waking when people were exposed to bright morning light versus dim conditions.

The wearables generating circadian scores

A growing crop of devices now translates light exposure, temperature, movement and heart-rate data into circadian metrics.

• Rhythm Ring measures light exposure and computes a “Circadian Score,” turning ambient light patterns into behavioral recommendations.
• Larcz uses a dual-wearable system, with one device worn and one placed in the environment, to surface the best times for natural light each morning and coach exposure habits.
• Oura Ring emphasizes morning sunlight in its education content, noting that first-thing sunlight suppresses melatonin and increases cortisol, and positions itself as a tool to track sleep and validate sunmaxxing habits.
• Fibion Krono was built specifically for circadian and sleep research, with sensors for blue-light exposure, high-precision skin temperature and multi-axis movement.
• Whoop is a screen-free fitness band that continuously tracks resting heart rate and heart rate variability, mapping sleep architecture and daily strain.
• The Gem Wearable, shaped like an Apple AirTag and worn on a pendant necklace, monitors sun exposure in real time and alerts the wearer when to seek shade based on skin tolerance, sunscreen habits and vitamin D needs.

The Gem’s approach is designed to fill a gap that generic UV forecasts miss. “[The Gem wearable] has a photodiode sensor that detects UVA, which is the aging UV, and UVB, which is the burning UV,” Stacy Salvi, CEO and co-founder of tech startup The90, told Glossy. “It’s important to understand that you can’t get that information from any weather app that you have on your phone, because that’s all based on UV index, which is like a weather forecast [with a] 100-mile radius [that] doesn’t really tell you anything about your personal exposure.”

Apps and circadian-coaching software

Not every entry point requires a new gadget. Several apps use existing phone sensors, or pair with lighting systems, to coach circadian habits.

• MyCircadian, an Android app, tracks sunrise and sunset, UV index and “sun sessions” while offering lux tools and coaching around optimal exposure times.
• MorningLux, an iOS app, measures ambient lux through the phone’s sensor and turns morning light exposure into a daily metric with personalized recommendations.
• OIO by Korrus markets itself as a circadian day-planning app, where users set an anchor wake time and OIO prescribes a morning bright-light window along with other daily light interventions.

Whether a circadian score becomes the next sleep score or fades as another wellness metric depends on how well the data actually changes behavior. But the underlying science, that light, timing and rhythm shape more of human health than we once realized, is not going anywhere.

This article was created by content specialists using various tools, including AI.