Retronasal Olfactory Function After Olfactory Training: A Prospective Single‐Arm Study

Background Retronasal olfaction is essential for aroma perception. Its impairment in individuals with olfactory dysfunction (OD) negatively affects dietary behaviour and quality of life. Regular exposure to odours in a form of olfactory training (OT) is used to rehabilitate the sense of smell. However, retronasal recovery following OT remains insufficiently characterised. Objective To verify whether OT improves retronasal odour identification and whether such improvement is related to orthonasal odour identification recovery. Study Design Prospective, single‐arm clinical study. Methods Fifty‐three patients with OD (predominantly post‐COVID‐19) completed at least 3 months of OT (conducted bi‐daily with four odours). Retronasal function was assessed with the ThreeT test and orthonasal function with the Sniffin’ Sticks battery before and after training. Results OT significantly improved both retronasal (9.40 ± 0.42 vs. 10.85 ± 0.48; p < 0.001) and orthonasal odour identification (8.75 ± 0.50 vs. 10.53 ± 0.50; p < 0.001). Changes in retronasal performance positively, moderately correlated with changes in orthonasal identification ( r = 0.38, p = 0.006). Clinically meaningful retronasal improvement was associated with a higher likelihood of orthonasal recovery, χ 2 (1) = 5.08, p = 0.024; OR = 4.00 (95% CIs: 1.16–13.83). Conclusions OT improves retronasal odour identification. The mechanisms of orthonasal and retronasal recovery may be partially overlapping.