Background/Objectives: A retrospective study was conducted to clarify the clinical characteristics of taste disorder cases at the Department of Oral Medicine of Hokkaido University Hospital. The subjects were 322 taste disorder patients (86 male, 236 female, average age: 66 (13.1) years, mean duration of disorder: 15.2 (20.0) months) who were treated at our department from 2007 to 2018. Methods: Associations between symptoms and classification were examined. Results: When looking at the taste symptoms, 154 cases of quantitative taste disorder were observed as taste loss, abscission, and dissociative taste disorder, and 168 cases of qualitative taste disorder were observed as spontaneous abnormal taste, dysgeusia, and maltaste. There was no relationship between sex and quantitative/qualitative taste disorders at V = 0.08. When looking at the causes of taste disorders, the majority were psychogenic, idiopathic, and oral diseases. Conclusions: Approximately 20% of taste disorders are caused by oral diseases, so it should be noted that oral diseases such as oral candidiasis and xerostomia can cause taste disorders and that many of them can be improved with oral treatment.

The relationships among bacterial flora, diseases, and diet have been described by many authors. An operational taxonomic units (OTUs) are the result of clustering the 16S rRNA gene sequences at a certain cutoff value, and they are considered compositional data. As Pearson’s correlation coefficient is difficult to interpret, Aitchison’s ratio analysis was used to develop a method to handle compositional data. Multivariate analysis was developed because univariate analysis can be subject to large biases. Simulations regarding absolute abundance based on certain assumptions and some analyses, such as nonparametric multidimensional scaling (NMDS), principal component analysis (PCA), and ratio analysis, were conducted in this study. The same content as a 100% stacked bar graph could be expressed in low dimensions using PCA. However, the relative diversity was not reproducible with NMDS. Various assumptions were made regarding absolute abundance based on the relative abundance. However, which assumptions are true could not be determined. In summary, ratio analysis and PCA are useful for analyzing compositional data and the gut microbiota.