The Rhythm app collects data on smartphone usage to estimate sleep duration, interruptions, and routine stability, providing a foundation for analyzing key indicators of circadian rhythms: interdaily stability (IS), relative amplitude (RA), and intradaily variability (IV). These non-parametric indicators quantify different aspects of daily rhythmicity, where IS reflects day-to-day rhythm consistency, RA measures the difference between daytime and nighttime activity, and IV examines hour-to-hour activity fluctuations within a day.

By using Rhythm to monitor these indicators, we can assess circadian rhythm disruptions and their correlation with various health conditions. For example, RAacti and ISacti are useful for tracking post-stroke rehabilitation, ISapp and ISacti help analyze obesity-related behaviors, and IVapp combined with RAacti provides insights into depressive symptoms. This capability positions Rhythm as a versatile tool with applications in sleep medicine, psychiatry, and rehabilitation, enabling long-term health monitoring and advancing our understanding of how daily routines impact overall well-being.

The technology behind “Rhythm” can automatically estimate sleep duration, sleep interruptions, and quantify routine stability based on smartphone usage behavior. With its advantage of extremely low power consumption, it enables long-term objective monitoring with higher recording accuracy. This technology also reflects users’ circadian rhythms, helping to understand the impact of smartphone usage before sleep on sleep quality, as well as the long-term effects of sleep behaviors on health. As a groundbreaking behavioral measurement method, it holds significant potential for clinical applications in fields such as sleep medicine and psychiatry.