The efficacy of olfactory training in improving olfactory function: a meta-analysis

Study the efficacy of olfactory training in smell recovery.

An extensive search was performed through different databases in order to find articles analyzing the efficacy of olfactory training as a treatment for olfactory dysfunction. Methodological quality of primary studies within the final sample was assessed following PRISMA guidelines. Standardized mean differences in pre–post olfactory training groups, and also in experimental-control and pre-follow up if possible, were computed by Hedges’ g effect size statistic. Each effect size was weighted by its inverse variance.

Final sample was composed of 36 articles (45 pre–post effect sizes). Contrasts were performed separately for odor identification, odor discrimination, odor threshold and general olfactory function. Moderate to large and heterogeneous effect was obtained for olfactory function (g = 0.755, k = 45, SE = 0.093, CI 95% = [0.572, 0.937]), different moderators had a significant effects, such as, training duration, age and anosmia diagnosis.

Olfactory training was found to have a positive and significant effect on rehabilitating the olfactory function.