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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.

Updated October 20, 2026

A cross-sectional study in JMIR Medical Informatics (2025) analysed data from 272 people in a citizen cohort in Daejeon, South Korea: 88 with metabolic syndrome and 184 with none of its criteria. Each wore a wrist device for at least five weekdays, recording heart rate, steps and sleep minute by minute. The researchers derived 26 indicators, including sleep markers (midsleep time, total sleep time) and circadian rhythm markers.

To see which indicators mattered most, the authors used explainable artificial intelligence (XAI). Circadian rhythm markers, especially those derived from heart rate, were more closely associated with metabolic syndrome than sleep markers.

A smiling woman on a park bench in the morning looks at her phone, a soft glowing panel of heart-rate, sleep and recovery charts floating beside her.
Ai-generated illustration

What metabolic syndrome is and why it matters

Metabolic syndrome combines abdominal obesity, insulin resistance, high blood pressure, high triglycerides and low HDL. It is associated with a higher risk of type 2 diabetes and cardiovascular disease.

Explainable Ai (XAI): the model explains its results

Unlike many Ai models, XAI does not just give a result: it shows which variables contributed most, in which direction and with what weight. In medicine that matters, because whoever reads a result needs to understand why the model says what it says. This study used three different methods: SHAP, an explainable boosting machine and a neural network for tabular data.

Recording sleep is one thing. Interpreting it is for your doctor.

The most important indicators

Across all the models, the most important marker was a new one proposed by the authors: circadian rhythm energy derived from heart rate (CCE), which was lower in people with metabolic syndrome. Other heart-rate markers, such as relative amplitude and the low-activity period, also mattered. Sleep markers did not reach statistical significance and appeared only as secondary factors. CCE kept its weight after adjusting for age, sex and BMI. It is a cross-sectional study: it describes an association in a group, not a personal risk.

A study is a starting point, not a conclusion.

The Digital Twin and this research

Heart rate and steps recorded by a watch or a wristband are the same kinds of data used in this study, but the study's circadian indicators are not a feature of the app. 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 estimate your risk of metabolic syndrome and it does not diagnose: this research describes groups of people, not you. Reading your values is for 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.

Their study. Your data.

Related reading

More studies, same rule: read the source.