Laryngopharyngeal Reflux and Olfaction Disorders. Is There Any Connection? A Scoping Review

Objectives: To review the evidence regarding olfaction in patients with laryngopharyngeal reflux. Methods: Conducting a scoping review of studies evaluating olfactory sense in patients with laryngopharyngeal reflux. Online databases were searched and studies evaluating laryngopharyngeal reflux impact on other nasal functions were excluded. Other exclusion criteria were the presence of severe nasal anatomical issues, rhinosinusitis, allergic rhinitis and nasal polyps in the study group. Results: Seven studies, between 2016 and 2019, met our inclusion criteria. Olfaction threshold was significantly lower in patients with laryngopharyngeal reflux than controls in three studies and in two of these studies, all three assessed parameters, including threshold, identification and discrimination, were significantly affected in the laryngopharyngeal reflux group. In three other studies, where the Connecticut Chemosensory Clinical Research Center test had been used, smell test scores were also statistically significantly lower in the reflux group. Finally, in a survey-based study evaluating olfaction, olfactory anomalies were positively related to gastroesophageal reflux disease and gastroparesis symptom severity. Conclusions: There is scarce evidence regarding the effect of laryngopharyngeal reflux on olfaction, but preliminary evidence shows that laryngopharyngeal reflux may cause olfactory abnormalities. Thus, olfactory abnormalities can be an additional reflux manifestation. Gastroparesis, gastroesophageal reflux disease, laryngopharyngeal reflux and Helicobacter pylori infection are factors that can potentially cause olfactory sensory disturbance.