For decades, the public health advice on sleep has been a single number: seven to eight hours. But a new study by Ultrahuman , developed with Stanford University’s Snyder Lab, Bangor University’s Hans-Peter Kubis, and La Trobe University’s Driller Lab, suggests that might only be half the story.
The other half might be consistency: keeping your sleep on a steady schedule from one night to the next. The study found that people with steadier sleep had lower overnight glucose, and that your heart rate while you sleep moves in step with your blood sugar.
The study is available as a preprint on medRxiv and hasn’t yet been peer reviewed.
The study
The Ultrahuman study analyzed 105,196 nights of data from 2,648 adults across 87 countries, all wearing an Ultrahuman Ring and a continuous glucose monitor at the same time between January 2024 and June 2025.
What makes the dataset unusual is that sleep and glucose were captured simultaneously, in everyday life, on the same people. Most sleep studies rely on a single sensor or take place in a lab. This study combined sleep and heart rate data from the Ultrahuman Ring with continuous glucose data from the M1 CGM, drawn from a consumer CGM program that has been collecting data for years.
The work builds on earlier Ultrahuman research published in Scientific Reports , with further work underway with Mayo Clinic, Harvard, Pfizer and Unilever .
What the data showed
The research team looked at two things, night by night, alongside overnight glucose: how steady each person’s sleep was, and their average heart rate during sleep.
Sleep consistency stood out as a long-term trait. People whose sleep length varied by an extra 30 minutes from night to night had about 4 mg/dL higher overnight glucose. It is a difference that builds up between people over time. On any single irregular night, the effect for the same person was small.
Sleeping heart rate told the night-to-night story:
- Overnight glucose was 5.7 mg/dL higher for every 10 bpm rise in a person’s own sleeping heart rate
- Between people, the gap was 6.5 mg/dL per 10 bpm
- Higher-heart-rate nights also came with less time in a healthy glucose range and more variable glucose
- 701 of the 911 people who wore both devices for at least two months showed the same pattern individually
- The link held across every BMI group and all five regions studied
The effects are modest, and the researchers are clear about that. Together they point in one direction: steadier sleep and a calmer heart rate overnight both go with healthier overnight glucose.
Why this matters
Chronically elevated blood sugar, even below the diabetic threshold, is linked to impaired cognition, disrupted appetite regulation, and a higher long-term risk of type 2 diabetes and cardiovascular disease. Those are two of the leading causes of preventable death globally.
What this dataset suggests is that how steadily you sleep, and how hard your heart is working while you do, may both be early signals worth paying attention to, long before anything would show up in a clinical test.
The encouraging part is that the most practical lever here doesn’t need a prescription or a gym membership: keep your sleep on a steady schedule, weekends included. And your Ring already tracks your sleeping heart rate, so you can see how your nights are going.
How health ecosystems can help
This study was only possible because two sensors were measuring the same person at the same time. That’s the underlying argument for an integrated health ecosystem: being able to see how systems in the body interact, rather than looking at sleep, glucose, heart rate and recovery in isolation.
It also opens up a second possibility. Once the relationship between sleep patterns and metabolic markers is mapped at population scale, it becomes possible to infer metabolic insights for people who don’t wear a CGM. The sensor data trains the model; the model can then read signal from the sensors people already have.
Regulators are moving in the same direction. The FDA is explicitly targeting connected health devices as tools for managing chronic disease, including pre-diabetes.
Conclusion
“We’ve long suspected that circadian consistency was upstream of metabolic health, and this dataset lets us see sleep regularity, heart rate and blood sugar moving together in everyday life,” said Ultrahuman CEO Mohit Kumar. “What’s striking is how accessible the habit is. Going to bed at roughly the same time each night is something anyone can start tonight.”
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