STUDY OBJECTIVES: Mitigating gender inequality in the diagnosis and management of sleep-disordered breathing (SDB) is of paramount importance. Historically, the diagnostic criteria for SDB were based on male physiology and did not account for variations in disease manifestation based on sex. Some payors use a definition of hypopnea that requires a 4% oxygen desaturation (AHI-4) to determine coverage for treatment, whereas the criteria recommended by the American Academy of Sleep Medicine require either a 3% oxygen desaturation or an arousal (AHI-3A). This study examined the diagnostic implications of these 2 definitions for men and women in a clinical setting. METHODS: We reviewed polysomnography reports for all patients who completed a diagnostic polysomnography study at 1 sleep disorders center in 2019. Every polysomnography recording was scored using both sets of criteria to determine AHI-4 and AHI-3A. RESULTS: Data from 279 women (64.7%) and 152 men (34.3%) were analyzed. Overall, the mean AHI-4 was 21.9 ± 27.3 and the mean AHI-3A was 34.7 ± 32.3 per hour of sleep. AHI-3A resulted in a diagnostic increase of 30.4% ( CONCLUSIONS: The definition of hypopnea used in the AHI-3A criteria is more consistent with the pathophysiology of SDB in women and results in higher rates of diagnosis. Use of the AHI-4 criteria may create a sex-based disparity in diagnosis, leading to symptomatic women remaining undiagnosed and untreated. CITATION: Haile K, Mungarwadi M, Ibrahim NA, et al. Using expanded diagnostic criteria mitigates gender disparities in diagnosis of sleep-disordered breathing.