Olfactory Training for COVID-19-Related Olfactory Dysfunction: A Systematic Review and Meta-Analysis of Randomized...

Area of Science:

• Otolaryngology
• Neurology
• Infectious Diseases

Background:

• The COVID-19 pandemic caused widespread olfactory dysfunction (OD), impacting patient quality of life (QoL).
• Persistent COVID-19-associated OD affects a significant patient subset, necessitating effective treatments.
• Olfactory training (OT) is a leading non-invasive therapeutic approach for OD.

Purpose of the Study:

• To systematically review and meta-analyze randomized controlled trials (RCTs) evaluating the efficacy of OT in patients with COVID-19-associated OD.
• To assess the impact of OT on objective olfactory function and QoL in this patient population.

Main Methods:

• A systematic review and meta-analysis of RCTs were performed using data from multiple databases (Web of Science, PubMed, Scopus, CENTRAL, Embase) up to June 2025.
• Ten RCTs involving 628 patients were included.
• Standardized mean differences (SMD) with 95% confidence intervals (CI) were calculated using STATA software to pool outcomes.

Main Results:

• Olfactory training demonstrated a significant improvement in objective olfactory scores compared to control groups (SMD=0.30, 95% CI [0.08, 0.51], p=0.01).
• OT also led to significant improvements in quality of life scores (SMD=-0.40, 95% CI [-0.65, -0.15], p<0.001).
• Low heterogeneity was observed for both primary and secondary outcomes (I²=33.69% and I²=37.47%, respectively).

Conclusions:

• Olfactory training is an effective intervention for improving olfactory function and QoL in patients experiencing persistent COVID-19-related olfactory dysfunction.
• While findings are positive, caution is advised due to variations in OT protocols and study designs.
• Further large-scale RCTs with standardized protocols are recommended to establish definitive clinical guidelines.