Olfactory dysfunction in patients with Parkinson's disease: A systematic review and meta-analysis

Abstract

Background: Parkinson's disease (PD) is a progressive neuro-degenerative disease and olfactory dysfunction is considered as an important issue in these patients. The prevalence of olfactory dysfunction in patients with PD was reported variously in previous studies. Therefore, we designed this systematic review and meta-analysis to estimate the pooled prevalence of olfactory dysfunction in patients with PD. Methods: Two expert researchers systematically searched PubMed, Scopus, EMBASE, Web of Science, Google Scholar, references of the papers, and conference abstracts. The titles and abstracts of the potential studies were evaluated after deleting the duplicates. We extracted data regarding the total number of participants, first author, publication year, the country of origin, mean age, mean disease duration, female/male, number with olfactory dysfunction, and name of the test. We evaluated the risk of potential bias by the Newcastle-Ottawa Quality Assessment Scale (adapted for cross-sectional studies). All statistical analyses were done using Stata software. To determine heterogeneity between the findings of included studies, inconsistency (I2) was calculated. We applied random effect model when I2 was more than 50. P-value less than 0.05 was considered significant.