The Influence of Obstructive Sleep Apnea and Nasal Continuous Positive Airway Pressure Therapy on Olfactory Function

Objective: To investigate the association between clinical sleep parameters and olfactory function (OF) in patients with obstructive sleep apnea (OSA) and to evaluate the therapeutic effect of 12-month continuous positive airway pressure (CPAP) on olfactory dysfunction (OD). Methods: A total of 146 participants were included: 55 healthy controls, 68 untreated OSA patients, and 23 CPAP-treated patients. OSA severity was classified according to the apnea–hypopnea index (AHI). OF was assessed using the Sniffin’ Sticks test. Clinical variables, sleep parameters, and olfactory scores were compared among groups. Subgroup analysis between CPAP-treated and untreated OSA patients used the Mann–Whitney U test. Multivariate logistic regression identified predictors of olfactory improvement. Results: Our findings demonstrated that OD was correlated with the severity of OSA. Olfactory scores were significantly negatively correlated with AHI ( r = −.544, P < .001), but positively correlated with average SpO 2 % ( r = .333, P = .006) and minimum SpO 2 % ( r = .449, P < .001). After 12 months of CPAP treatment, the mean olfactory score reached 13.87 ± 1.96, significantly higher than 9.78 ± 4.217 in the untreated group, demonstrating substantial functional recovery. Conclusion: The results indicated a close relationship between OD and disease severity in patients with OSA and confirmed that long-term CPAP therapy can effectively improve OF. These findings provide new insights into the multisystem impact of OSA and suggest that olfactory assessment may serve as a complementary clinical tool for OSA evaluation.