Detection of Cyclic Variation in Heart Rate (CVHR) During Sleep Using a Ring-Type Silicon Sensor and Evaluation of Intra-Weekly Variability

Patients with sleep apnea syndrome (SAS) have a risk of stroke that is more than three times higher than that of healthy individuals. Early detection and appropriate treatment are crucial for preventing serious complications, and detecting cyclic variation in heart rate (CVHR) plays a key role in early diagnosis. This study investigated the feasibility of detecting CVHR during sleep using a wearable, comfortable device and evaluated the ability to assess weekly fluctuations. Heart rate, blood oxygen saturation, and bio-acceleration were measured for seven consecutive nights in eight healthy subjects (45.7 ± 10.1 years old). The CVHR values obtained using a ring-type sensor were compared to those derived from the apnea–hypopnea index (AHI) measured with a Holter ECG. The results revealed that CVHR values measured with the ring-type sensor were higher than those measured with the Holter monitor. Although correction is required, the ring-type sensor successfully detected intra-weekly fluctuations. These findings suggest that a ring-type sensor could be a practical tool for monitoring CVHR and identifying weekly trends in a comfortable, non-invasive manner.