Efficacy of olfactory training in chronic rhinosinusitis patients with olfactory dysfunction: A comparative study of different initiation timings

To investigate whether differences exist in the improvement of olfactory function based on the initiation timing of Olfactory Training (OT) in patients with Chronic Rhinosinusitis with Olfactory Dysfunction (CRSwOD) following Functional Endoscopic Sinus Surgery (FESS). A single-center, prospective, randomized controlled study was conducted. We analyzed 101 patients who underwent endoscopic sinus surgery in our department of Otorhinolaryngology-Head and Neck Surgery between October 2024 and April 2025. Patients were randomized into four groups: Group A ( n = 22), Group B ( n = 19), Group C ( n = 20), and Group D ( n = 40). All patients underwent a comprehensive preoperative olfactory assessment, including an Olfactory Identification Test (OIT), Olfactory Threshold Test (OTT), and a Visual Analogue Scale (VAS) for subjective smell perception. Postoperatively, all patients received standardized medical therapy, including systemic antibiotics and corticosteroids, as well as topical corticosteroid nasal sprays and nasal saline irrigation. In addition to this standard medical therapy, Groups A, B, and C underwent OT. Group A initiated OT within 24 h post-surgery, Group B began OT one week post-surgery, and Group C started OT two weeks post-surgery. The OT duration for all three groups was 3 months. Follow-up assessments (using the same OIT, OTT, and VAS measures) were conducted for Groups A, B, and C at 1, 2, and 3 months after the initiation of their respective OT regimens. Group D (control) was assessed at 1, 2, and 3 months post-surgery. No statistically significant differences were observed in the preoperative OIT, OTT, and VAS scores among the four groups. Following the 3-month intervention, the OIT scores of all four groups were significantly higher than their preoperative baselines (P < 0.05), while their VAS scores were significantly lower (P < 0.05). At the 2-month post-intervention mark, the OTT scores of Groups A, B, and C showed a significant increase compared to their preoperative levels (P < 0.05). After 3 months, the OIT and OTT scores in Groups A, B, and C were significantly higher than those in Group D (P < 0.05), and their VAS scores were significantly lower than those in Group D (P < 0.05). Furthermore, upon comparing the three OT groups after the 3-month training period, Group B demonstrated significantly higher OTT and OIT scores than both Group A and Group C (P < 0.05). OT is an effective adjunctive therapy for improving olfactory dysfunction in CRSwOD patients after FESS. This study provides the first evidence that the initiation timing of OT is a critical factor influencing therapeutic outcomes. The one-week postoperative time point appears to be the optimal window for commencing OT, as initiation either earlier or later than this point resulted in inferior outcomes.