Multimodal Monitoring of Interstitial Glucose and Physiological Signals During Sleep Using Minimally Invasive and Ring-Type Sensors: A Pilot Study

In this pilot study, five healthy participants (1 female) simultaneously wore a minimally invasive interstitial fluid glucose (ISFG) sensor and a ring-type wearable device that continuously recorded heart rate (HR), peripheral oxygen saturation (SpO₂), and actigraphy during sleep (00:00–06:00). Multimodal time-series analyses were performed to characterize associations between ISFG fluctuations and physiological parameters. ISFG levels decreased during sleep in four of five participants. In participants 1, 3, 4, and 5, ISFG increased between 12:00–15:00, followed by a gradual decline toward the night. Paired t-tests demonstrated significantly lower ISFG levels during the latter half of the sleep period compared with the first half (0–3 h vs. 3–6 h, n = 5, p = 0.01). In addition, four participants exhibited a mild decrease in SpO₂ between 03:00–04:00, while one dataset was incomplete. These preliminary findings suggest that nocturnal ISFG reduction may be associated with subtle alterations in oxygen saturation dynamics. Integration of minimally invasive glucose monitoring with ring-type wearable devices offers a promising approach for detecting unrecognized nocturnal hypoglycemia and may enhance remote healthcare services through real-time physiological risk assessment. Future studies with larger cohorts are needed to validate these observations and facilitate clinical application.