3. Results
The demographic and clinical characteristics of the enrolled subjects
are summarized in Table 1. Table 1 presents the descriptive statistics
from the objective test-based gustatory dysfunction perspective. In
total, 180 subjects were identified as having normal gustatory function,
and 39 were identified as having gustatory dysfunction. The mean age was
46.0 ± 18.8 years in the normal gustatory function group and 56.5 ± 18.1
years in the gustatory dysfunction group. The difference in age between
the two groups was statistically significant (p = 0.0016). The
composition of sex and the prevalence of diabetes mellitus (DM) were
statistically significant (p = 0.001). The prevalence of
hypertension and the proportion of smokers were not different between
the two groups.
Regarding subjective olfactory function, the proportions of subjective
normosmia, hyposmia, and anosmia in the normal gustatory function group
were 8.3%, 20%, and 71.7%, respectively. In the gustatory dysfunction
group, the proportions of subjective normosmia, hyposmia, and anosmia
were 38.5%, 25.6%, and 35.9%, respectively. There was a statistically
significant difference between the two groups (p <
0.0001). Regarding objective test-based olfactory function, the
proportions of normosmia, hyposmia, and anosmia were 43.3%, 18.3%, and
38.4%, respectively, in the normal gustatory function group. In the
gustatory dysfunction group, the proportions of normosmia, hyposmia, and
anosmia were 46.2%, 33.3%, and 20.5%, respectively. There was a
statistically significant difference between the two groups (p =
0.041). The mean threshold, discrimination, identification, and TDI
scores also significantly differed between the two groups (p< 0.0001).
Next, the relationships between objective gustatory function and the
other variables were evaluated. Among the exploratory variables, age,
sex (male), DM, subjective olfactory function, threshold,
discrimination, identification, and TDI scores were significantly
associated with the presence of objective gustatory dysfunction in the
univariate analysis (Table 2). In the multivariate analysis, age, sex,
objective olfactory function, threshold, and discrimination score were
selected based on the AIC criteria. Age, sex (male), and objective
olfactory function were positively associated with objective gustatory
dysfunction, and the threshold and discrimination score were negatively
associated with objective gustatory dysfunction. However, when the
relationships between subjectively recognized gustatory function and
other variables were evaluated, smoking (p = 0.028) and
subjective olfactory function (p = 0.007) were positively
associated with subjective gustatory dysfunction in the univariate and
multivariate analyses (Supplementary Table 1). Figure 1 shows the violin
plots for the continuous variables (age, threshold, discrimination,
identification, and TDI) for the objective gustatory function. As shown
by the mean and variance information in Table 2 and Supplementary Table
2, there were no significant differences among the continuous variables
for subjective gustatory dysfunction (Figure 1A). However, for the
test-based objective gustatory function, differences were observed in
all the continuous variables (Figure 1B). Significant differences were
observed in the threshold, discrimination, identification, and TDI. This
was confirmed by the fact that the p -values for these variables
were less than 0.0001 (Table 2).
Finally, the relationships between objective gustatory function and
other clinical variables were investigated according to age (age ≥ 60
years and age < 60). Since there were only two patients with
hypertension in the under 60 group, the logistic regression did not
converge, and hypertension was excluded from the analysis. In the group
aged less than 60, subjective olfactory function, threshold,
discrimination, identification, and TDI score were significant variables
in the univariate analysis, and sex (male) (p = 0.046) was
positively associated with objective gustatory dysfunction and the
threshold score (p = 0.013) and discrimination score (p =
0.010) were negatively associated with objective gustatory dysfunction
in the multivariate analysis. In the group aged ≥ 60 years, sex (male),
subjective olfactory function, threshold, identification, and TDI score
were significant variables in the univariate analysis. Sex (male)
(p = 0.012) was positively associated with objective gustatory
dysfunction, and the threshold score (p = 0.0312) was negatively
associated with objective gustatory dysfunction in the multivariate
analysis (Table 3).