목적: The Apnea-Hypopnea Index (AHI), used to assess the severity of sleep apnea, can show daily variability due to various factors such as sleep quality, position, and alcohol consumption. However, polysomnography (PSG), the standard diagnostic test, is difficult to perform repeatedly due to time and cost constraints, making it challenging to validate the representativeness of a single measurement. Our group previously reported a significant correlation between PSG- measured AHI and smartwatch-estimated AHI. Based on this, we evaluated AHI variability over one month using smartwatch measurements in the same patients. 방법:Adult patients presenting with suspected Obstructive Sleep Apnea (OSA) symptoms were prospectively recruited from June 2023 to December 2024. Participants wore a Samsung Galaxy Watch 6 (Samsung Electronics Co., Ltd.) every night for one month to measure AHI during sleep. Additionally, they underwent Type 1 PSG while simultaneously wearing the smartwatch on one day during the study period. One-sample t-tests were performed to evaluate differences between PSG-day AHI and one- month mean AHI values, and Clinically Important Mean Difference (CIMD) analysis was conducted to assess whether differences exceeding certain thresholds were clinically significant. 결과:A total of 53 patients were included in the analysis, with a mean age of 42.2 ± 11.8 years, of whom 38 (71.7%) were male and 15 (28.3%) were female. The average sleep measurement period per patient was 19.8 ± 6.7 days (range: 5-30 days), with a mean sleep duration of 358.2 ± 45.3 minutes (range: 180.0-650.4 minutes). One-sample t-tests revealed significant differences between PSG-day AHI and one-month mean AHI in 42 patients (79.2%). CIMD analysis showed that 21 patients (39.6%) had differences of ±10 or greater between PSG-day AHI and one-month mean AHI values. 결론:Single PSG-measured AHI values appeared to differ from one-month mean AHI values in most patients, with different severity classifications observed in a considerable portion of patients. Therefore, daily variability should be considered when making clinical judgments based on single PSG test results.