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

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.

To verify whether OT improves retronasal odour identification and whether such improvement is related to orthonasal odour identification recovery.

Prospective, single-arm clinical study.

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.

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, χ²(1) = 5.08, p = 0.024; OR = 4.00 (95% CIs: 1.16-13.83).

OT improves retronasal odour identification. The mechanisms of orthonasal and retronasal recovery may be partially overlapping.