Early detection of obstructive sleep apnea (OSA) is critical due to its link to cardiovascular diseases. Our previous study validated an algorithm-based photoplethysmography (PPG) smartwatch for OSA risk detection. This study aimed to characterize OSA features and assess its association with arrhythmia risk among smart wearable device (SWD) consumers in China in a real-world setting. Between December 15, 2019, and January 31, 2022, SWD consumers across China were screened for OSA risk using HUAWEI devices. OSA diagnosis was confirmed via telecare follow-ups, including clinical evaluations and sleep test records. Disease characteristics and arrhythmia risks were analyzed. In a large cohort of 1,056,494 participants, smart wearable devices (SWDs) effectively identified 19,563 individuals at high risk for OSA, with 1054 confirmed cases. OSA patients demonstrated high prevalence of obesity (46.8%), hypertension (19.8%), and arrhythmia (17.17%). SWDs detected abnormal heart rhythms or suspected arrhythmia in 95.9% of confirmed OSA cases. Age emerged as an independent predictor of arrhythmia risk, while hypertensive OSA patients were older, more obese, and experienced prolonged nocturnal hypoxia (Time length of SpO<90%, P=0.020). These findings underscore the utility of SWDs in OSA screening and highlight the significant cardiovascular risks associated with OSA. PPG-based SWD effectively screened for OSA and identified elevated arrhythmia risks. These findings support their utility for large-scale OSA screening and highlight cardiovascular risks management. Mobile Health (mHealth) technology for improved screening, patient involvement and optimizing integrated care in atrial fibrillation. ChiCTR-OOC-17014138. 2017-12-26. 2018-11-18.