Using Wearable Sensors to Capture the Synchrony of Circadian Rhythms Across Physiological Processes in Free-living Conditions

Biological rhythms, such as the circadian rhythm, are cycles in our physiology and behaviour that can be important predictors of poor health. Wearable sensors offer the potential to measure these rhythms across multiple aspects of our physiology simultaneously, allowing a detailed assessment of circadian cycles and a measure of circadian synchronisation across physiological processes. However, multi-modal measurement poses methodological challenges in terms of acceptability to participants, and data integration. Here we investigate the concurrent use of a smartwatch, continuous glucose monitor, and ambulatory electrocardiogram over two weeks in a sample of 7 participants. We assess the the acceptability of each wearable sensor, demonstrate methods for extracting circadian fluctuations in 6 bio-behavioural metrics, and calculate a measure of phase-locking (synchrony) between them as a novel marker of circadian health. This further develops the potential of wearable health sensors to be used in biological rhythm research, and for integrating a measure of circadian rhythm synchrony into wearable health monitoring systems.