Can immersive olfactory training serve as an alternative treatment for patients with smell dysfunction?

Objectives: Olfactory training (OT) has emerged as a first-line therapeutic approach to the management of olfactory dysfunction. Conventional OT (COT) involves the systematic home-based exposure to four distinct odors. Previous research has demonstrated that immersive OT (IOT) involving full-body exposure to dozens of distinct odors could also improve overall olfactory function. This study compared IOT and COT in terms of efficacy.

Methods: A total of 60 patients were enrolled and assigned to three groups. The IOT group ( = 25) underwent immersive exposure to 64 odors once daily in a specialized theater. COT participants ( = 17) sniffed four typical odors in a set of four jars twice daily at home. A control group ( = 18) underwent passive observation. Olfactory function was assessed before and after training.

Results: Significant improvements in composite threshold-discrimination-identification (TDI) scores were observed after training in both the IOT (mean difference = 2.5 ± 1.1.  = .030) and COT (mean difference = 4.2 ± 1.3,  = .002) groups. No changes were observed in the control group. A significantly higher proportion of patients in the COT group (41%) presented improvements of clinical importance (TDI ≥5.5) compared to the controls ( = .018). The improvements attained in the IOT group (20%) were less pronounced ( = .38).

Conclusion: While IOT did not exhibit the same efficacy as COT in restoring olfactory function, it still demonstrated promising outcomes. Future efforts to advance olfactory recovery should focus on cross-modal integration.

Level Of Evidence: Level 3.