Does positive airway pressure therapy improve olfactory function?

Olfactory function deteriorates in patients with severe obstructive sleep apnea syndrome (OSAS). The effect of positive airway pressure (PAP) therapy on olfactory function has not been investigated before. In this study, we aimed to investigate the role of PAP therapy on olfactory impairment in patients with OSAS.

Thirty patients who had OSAS and planned for PAP therapy were included in the study. All participants underwent a detailed otorhinolaryngological examination and polysomnography. The "Sniffin' Sticks" test was used for the analysis of olfactory function. The participants underwent the smell test before the PAP therapy, and about 3 months after the therapy. Pretreatment and posttreatment results were compared.

The pretreatment and the posttreatment apnea-hypopnea index (AHI) were 57.6 ± 29.8/hour and 9.5 ± 7.9/hour, respectively. Odor threshold (OT), odor discrimination (OD), odor identification (OI), and threshold-discrimination-identification (TDI) scores significantly increased after PAP therapy (p = 0.001, p = 0.002, p = 0.001, and p = 0.001, respectively). The pretreatment and posttreatment total TDI scores were 28.48 ± 4.71 and 32.50 ± 3.88, respectively (p = 0.001).

This study demonstrates olfactory dysfunction in patients with OSAS. We achieved a significant improvement in olfactory function of patients with OSAS after PAP therapy. Further studies are needed to illuminate the pathogenesis of olfactory dysfunction in OSAS, and the role of PAP therapy on olfactory improvement.