Short Sleep Duration Measured by Smartwatch Is Associated With Elevated Resting Heart Rate and Reduced Nocturnal Oxygen Saturation: Insights From Heartbeat

Introduction Sleep duration has been shown to impact cardiovascular outcomes; however, the impact on wearable‐derived metrics such as oxygen saturation and resting heart rate remains underinvestigated. This study aims to determine whether average sleep duration of ≤ 6 h per night impacts resting heart rate (RHR) and maximum nocturnal oxygen saturation (MaxSpO₂). Methods Using data from the HEARTBEAT study, sleep duration and maximum oxygen saturation during sleep were collected via the Samsung Galaxy Watch. Participants were stratified into two groups based on average sleep duration (≤ 6 h vs > 6 h per night) and propensity‐matched for baseline characteristics. The primary outcomes were RHR and MaxSpO₂. Statistical analysis was performed using R, version 4.5.1. Results After propensity score matching, there were 168 patients in each group with well‐balanced baseline characteristics and comorbidities. Participants with average sleep duration ≤ 6 h demonstrated higher RHR compared to those with average sleep duration > 6 h (61.0 ± 5.8 bpm vs 57.7 ± 6.8 bpm; p < 0.001). Additionally, MaxSpO₂ was lower in the group with shorter sleep duration (95.1 ± 2.4% vs 96.2 ± 1.5%; p < 0.001). Conclusion Sleeping ≤ 6 h per night is associated with higher resting heart rate and lower maximum nocturnal oxygen saturation.