[Progress in research on olfactory dysfunction in patients with obstructive sleep apnea]

Obstructive sleep apnea （OSA） is a common sleep-related breathing disorder characterized by recurrent upper-airway collapse and intermittent hypoxia, which has been widely recognized for its detrimental effects on neurocognitive function and multiple physiological systems. Emerging evidence indicates that olfactory dysfunction （OD） may represent an important yet long-overlooked manifestation in patients with OSA. Numerous clinical studies have demonstrated that olfactory threshold, discrimination, and identification abilities are significantly impaired in individuals with OSA compared with healthy controls, and the severity of olfactory deficits shows a clear negative correlation with the apnea-hypopnea index. The underlying mechanisms appear to be multifactorial:①damage to the cholinergic neurotransmitter system and cognitive impairment induced by intermittent hypoxia and sleep fragmentation;②structural and functional alterations in brain regions involved in olfactory processing, including the prefrontal cortex, hippocampus, and thalamus;③the impact of elevated body mass index and chronic inflammatory responses on the olfactory epithelium and central olfactory pathways. Continuous positive airway pressure （CPAP）, the first-line therapy for OSA, may partially improve olfactory performance by enhancing ventilation, reducing hypoxemia, and alleviating airway inflammation, although current evidence remains limited by sample size and follow-up duration. Beyond standard OSA management, olfactory training, neurophysiological assessment, and inflammation-modulating interventions may serve as promising future strategies. In summary, OD is highly prevalent and clinically significant in OSA patients, with a complex pathophysiological basis involving multiple interacting factors. Larger-sample, mechanism-driven, and intervention-focused studies are warranted to deepen our understanding of OSA-related OD and to support the development of more precise therapeutic approaches.