Daily rhythm and metabolic syndrome: a study of 272 adults
Study of 272 adults with a wrist device: metabolic syndrome was linked more to heart rate rhythms than to sleep. An association, not a cause.
Blog · Sleep
Sleep and atrial fibrillation: a study of 52,952 people
Study of 52,952 people with wearable devices: less deep and REM sleep was linked to more atrial fibrillation. An association, not a cause.
The study, published in JACC: Advances (2025), analyses the association between sleep stages measured with wearable devices and the development of atrial fibrillation in 52,952 participants from the All of Us Research Program, followed for a median of 935 days. Over that period, 437 people developed atrial fibrillation.
The concrete numbers
Participants who went on to develop atrial fibrillation already showed, at the start of the study, shorter deep sleep (0.82 versus 0.98 hours, p<0.001) and shorter REM sleep (1.14 versus 1.31 hours, p<0.001) than those who did not.
In both cases the difference is about ten minutes a night, seen on average across a very large group.
“Independent”: what it means
Longer total sleep, less deep and REM sleep and more light sleep are independently associated with the risk of atrial fibrillation.
“Independent” means the finding holds even after taking into account age, sex, BMI, hypertension, diabetes and other traditional risk factors. The authors point to a possible role in risk stratification and prevention.
What remains
It is an observational study: it shows an association in a group. It does not show that changing your sleep stages protects your heart, and it says nothing about the risk of any single person.
One night is a data point. Months of nights are a story.
The Digital Twin and this research
The Digital Twin lines up the data your devices write to your phone, such as steps, heart rate and sleep, and shows you how they change over time. It does not build cardiovascular risk profiles and it does not diagnose: this research describes groups of people, not you. These are data to read together with your doctor.
The source is at the bottom. Open it.
The source
This summary starts from research by others. It is not medical advice for you: talk it over with your doctor.
- Yazdanpanah et al., JACC: Advances (2025/2026), (opens in a new tab)pmc.ncbi.nlm.nih.gov
Their study. Your data.
Related reading
Early Parkinson’s and REM disorder: a study of 413 people
Study of 413 people with early Parkinson's: probable REM sleep behaviour disorder was linked to faster cognitive decline. An association, not a cause.
Irregular sleep and the heart: a study of 1,992 adults
Study of 1,992 adults: highly variable sleep duration and timing were linked to about double the cardiovascular risk. An association, not a cause.
More studies, same rule: read the source.