BACKGROUND: Obstructive sleep apnea-hypopnea syndrome (OSAHS) affects over 936 million adults globally. Recently, it has been found to contribute to gait disorders, but there is limited information regarding how various indicators of OSAHS affect gait patterns. METHODS: A total of 136 subjects recruited from Nanjing Drum Tower Hospital were categorized based on apnea hypopnea index (AHI) and oxygen saturation (SpO), respectively. All subjects underwent data collection regarding demographics, gait testing, sleep monitoring, multimodal magnetic resonance imaging (MRI), and a battery of clinical evaluations. RESULTS: Subjects with elevated AHI exhibited increased step width and decreased stride length in comparison to those with lower AHI. The nm (no or mild)-hypoxemia group demonstrated faster stride frequency than the ms (moderate to severe)-hypoxemia group. High-frequency obstructive sleep apnea-hypopnea resulted in cortical atrophy of the orbital part of right inferior frontal gyrus and upregulation of functional connectivity between the basal ganglia and left inferior temporal gyrus, basal ganglia and left insula, while the severity of hypoxemia led to functional alternations between right angular gyrus and left gyrus rectus, which manifested as respective alternations in gait. The area under the curve (AUC) for gait tests evaluating moderate-to-severe OSAHS was 0.842, using logistic regression models. CONCLUSION: The frequency of respiratory events and the severity of hypoxemia caused different gait dysfunction and corresponding underlying mechanisms in patients with OSAHS. Gait testing might be a potential tool for rapidly screening OSAHS in the population.