“Modified Olfactory Training in Patients With Post-Infectious Olfactory Loss”, Aytug Altundag, Melih Cayonu, Gurkan Kayabasoglu, Murat Salihoglu, Hakan Tekeli, Omer Saglam, Thomas Hummel2015-06-02 (human olfaction)⁠:

Objective: Patients with olfactory dysfunction benefit from repeated exposure to odors, so-called olfactory training (OT). This does not mean occasional smelling but the structured sniffing of a defined set of odors, twice daily, for a period of 4 months or longer. In this prospective study, we investigated whether the effect of OT might increase through the use of more odors and extension of the training period.

Study Design & Methods: This study shows OT results when performed with 4 or 12 odors for 36 weeks in patients with post-infectious olfactory dysfunction. A total of 85 subjects participated (mean age 45.6 ± 10.5 years, range 24–68 years). 3 groups were formed: (1) In the modified olfactory training (MOT) group, patients used three sets of 4 different odors sequentially. (2) Participants in the classical odor training (COT) group used 4 odors. (3) Participants in the control group did not perform OT. All groups were matched for age and sex distribution of participants.

Results: Both participants in the COT and MOT groups reached better scores than controls in terms of odor discrimination and odor identification. Continuing OT with 4 different odors after the 12^th and 24^th weeks produced better results in terms of odor discrimination and odor identification scores as compared to using the same 4 odors throughout the entire study.

Conclusion: This study confirmed the effectiveness of OT. Increasing the duration of OT and changing the odors enhances the success rate of this therapy.