The Impact of Reduced Salivary Flow Rate and Aging on Oral Candidiasis in Patients with Stomatitis

doi:10.21203/rs.3.rs-4877239/v1

Download PDF

Research Article

The Impact of Reduced Salivary Flow Rate and Aging on Oral Candidiasis in Patients with Stomatitis

https://doi.org/10.21203/rs.3.rs-4877239/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

Aim: We elucidated the relationship between the comorbidity of oral candidiasis and stomatitis and a reduced salivary flow rate, and identify predictors for oral candidiasis.

Methods: A total of 259 patients with stomatitis (mean age 59.77±15.93 years, range 10 –87 years, 201 females) were diagnosed with oral candidiasis through Candida albicansculture test. Clinical characteristics of the Candida–positive and Candida–negative groups were statistically analyzed.

Results: Out of the total 259 stomatitis patients, 81 (31.27%) had oral candidiasis based on Candida albicans culture. Regarding age, the stomatitis with oral candidiasis group (64.25 ± 14.66 years) was significantly older than the stomatitis without oral candidiasis group (57.73 ± 16.10 years) (p=0.002). Regarding salivary flow rates, both unstimulated salivary flow rate (UFR) (0.36 ± 0.32 mL/min vs. 0.47 ± 0.28 mL/min, p=0.006) and stimulated salivary flow rate (SFR) (1.21 ± 0.68 mL/min vs. 1.41 ± 0.69 mL/min, p=0.032) were significantly lower in patients with oral candidiasis compared to those without. The proportion of xerostomia based on UFR 0.2mL/min (xerostomia_UFR) was significantly higher in the stomatitis with oral candidiasis group (49.4%) compared to the stomatitis without oral candidiasis group (18.5%) (p<0.001). Similarly, the proportion of xerostomia based on SFR of 0.7mL/min was significantly higher in the stomatitis with oral candidiasis group (27.2%) compared to the stomatitis without oral candidiasis group (10.7%) (p<0.001). The prediction accuracy of oral candidiasis based on age was 62.2% (AUC=0.622, 95% CI: 0.547-0.696, p=0.002), with a cutoff value of 64.50 years for age. The prediction accuracy based on UFR was 65.8% (AUC=0.658, 95% CI: 0.582-0.734, p<0.001), with a cutoff value of 0.3350 mL/min for UFR. The prediction accuracy based on SFR was 58.7% (AUC=0.587, 95% CI: 0.510-0.663, p=0.025), with a cutoff value of 1.150 mL/min for SFR. From the generalized linear model for oral candidiasis, xerostomia_UFR was significant predictor (B=0.328, 95% CI: 0.177 - 0.480, p<0.001).

Conclusion: Although a decrease in salivary flow rate and aging were associated with the occurrence of oral candidiasis in patients with stomatitis, these factors alone did not result in high predictive accuracy.

oral candidiasis

Candida albicans

xerostomia

salivary flow rate

age

elderly

Stomatitis is an umbrella term for inflammation of the mouth and lips and encompasses all inflammatory processes affecting the mucous membranes of the oral cavity and lips, regardless of the presence of oral ulcers [1]. The term is derived from the Greek word "stoma," meaning "mouth," and the suffix "-itis," indicating "inflammation." Stomatitis can present with various etiologies and manifestations, including a range of clinical conditions such as aphthous stomatitis, angular cheilitis, denture-related stomatitis, allergic contact stomatitis, migratory stomatitis, and herpetic gingivostomatitis [2]. The prevalence of stomatitis varies widely, ranging from 19–79% [3, 4]. Despite the high prevalence of stomatitis in humans, clinical studies aimed at elucidating its aetiopathophysiology and clinical characteristics remain insufficient.

However, the etiology of stomatitis remains unclear. Common causes of stomatitis include contamination by microorganisms, such as fungi or yeast; viral infections; xerostomia; inflammation; nutritional deficiencies in iron, folic acid, zinc, and members of the vitamin B family (riboflavin, pyridoxine, cobalamin, and niacin); poor oral hygiene; smoking; and oral trauma [5–7]. Additionally, allergic reactions, various medically compromised conditions, side effects following radiation therapy, diabetes mellitus, and genetic factors are associated with stomatitis [4, 6, 8, 9]. Regarding SARS-CoV-2, the pathogen responsible for the coronavirus disease 2019 (COVID-19) pandemic, the most common oral symptoms are xerostomia and stomatitis, which are present in 40% of cases [10]. Xerostomia refers to the sensation of oral dryness, and stomatitis due to viral infections may occur in conjunction. Xerostomia is the quantitative reduction in saliva that exhibits anti-viral and anti-fungal effects [11]. In a recent meta-analysis, xerostomia and oral candidiasis were found to be closely interrelated [12]. Consequently, individuals with xerostomia may have increased susceptibility to microbial infections. In this study, we focused on the interconnections among stomatitis, candidiasis, and xerostomia.

Candida albicans infections are among the most common fungal infections of the oral cavity, with Candida spp. being one of the leading fungal pathogens affecting humans. Oral candidiasis is an opportunistic infection affecting the oral mucosa and is caused by the increased virulence of commensal Candida species. Candida albicans is the causative agent of various forms of stomatitis, including denture-related stomatitis, angular cheilitis, and median rhomboidal glossitis [13–15]. Candida albicans is a robust gram-positive dimorphic yeast that can exist as a normal commensal in the oral cavity of healthy individuals and patients with stomatitis. Approximately 18% of healthy young people are carriers of Candida albicans [13]. The primary location of Candida albicans in the oral cavity is the posterior tongue and other oral sites, such as the mucosa and gingiva, while secondary colonization occurs on dental surfaces and plaque over dental prostheses [16]. The significance of oral-derived Candida albicans extends beyond stomatitis, as it can penetrate blood vessels and cause severe brain diseases in premature infants and the elderly [17, 18]. Particularly in the elderly, Candida infections are a significant and expanding clinical problem [19]. This is attributed to the prevalence of polypharmacy, reduced salivary flow rates, and higher likelihood of frailty or concurrent systemic diseases.

The occurrence of stomatitis and candidiasis not only reduces the patient's quality of life but also increases pain and discomfort in the mouth. This study hypothesized that the co-occurrence of oral candidiasis in patients with stomatitis may have significant clinical implications. Specifically, we aimed to determine whether oral candidiasis is correlated with a reduction in salivary flow rate, extension of symptom duration from onset, and an increase in subjective pain intensity. We also investigated the principal factors that could predict oral candidiasis and evaluated their predictive accuracy. Additionally, this study aimed to determine whether oral candidiasis occurs more frequently as age increases in patients with stomatitis by examining individuals across a broad age spectrum (from teens to 80s).

Procedures involving human subjects were conducted following the ethical standards of the Committee on Human Experimentation at our institution and the 1975 Declaration of Helsinki. This study was approved by the Ethics Review Board of Kyung Hee University Dental Hospital (IRB No. KH-DT23022). Informed consent was obtained from all the participants involved in this study. Informed consent was obtained from all participants. For participants under the age of 16 years, informed consent was obtained from their parents or legal guardians.

Study population and study design

This observational study included consecutive patients presenting with stomatitis at the Department of Orofacial Pain and Oral Medicine of Kyung Hee University Dental Hospital between January 2022 and May 2024. A total of 259 patients (58 males and 201 females; mean age: 59.77 ± 15.93 years; range: 10–87 years) were included. Subject selection was based on a standardized clinical examination. The male-to-female ratio of patients with stomatitis is 1:3.47. Patients were divided into two groups based on the presence or absence of oral candidiasis. Their clinical characteristics, unstimulated and stimulated salivary flow rates, presence of xerostomia based on each salivary flow rate, and prevalence of common systemic diseases was investigated and analyzed. Among the 259 patients with stomatitis, 81 patients (69 females and 12 males; mean age 64.25 ± 14.66 years) had oral candidiasis (defined as a level of a few or more in Candida albicans culture), while 178 patients (132 females and 46 males; mean age 57.73 ± 16.10 years) did not have oral candidiasis. Thus, we divided the patients into two groups for the analysis: stomatitis without oral candidiasis and stomatitis with oral candidiasis. We collected data and conducted various analyses to identify factors associated with oral candidiasis in the entire cohort of 259 patients, as well as differences in outcomes based on the presence or absence of oral candidiasis. Patients with insufficient data for analysis or unclear Candida albicans culture results were excluded.

1) Diagnosis of oral candidiasis

Candida cultures were performed on oral lesions by an oral medicine specialist on the first day of their visit. The area of the patient's mouth that experienced pain or discomfort was swabbed using a sterile cotton applicator of Copan Transystem™ (COPAN Italia S.p.A., Brescia, Italy) and inoculated onto a culture dish containing Sabouraud dextrose agar. The dish was covered, sealed with paraffin wax, and incubated at 30°C. The observation period spanned four weeks, with daily observations during the first week. From the second week onward, the intervals between observations were gradually extended to monitor the growth of Candida albicans. The final analysis and conclusions were drawn at the end of the fourth week. The results were categorized into four stages based on the quantity of Candida albicans cultured, as indicated by the area and density: none (no growth), few (covering less than half of the medium), moderate (covering more than half of the medium), and many (colonies covering most of the medium).

2) Clinical characteristics

Subjective pain intensity was assessed using a visual analog scale (VAS). Pain was rated on an 11-point scale ranging from 0 to 10, with 0 indicating no pain and 10 indicating the worst possible pain. The patients were instructed to rate their pain accordingly, and their self-reported scores were recorded. Thus, scores closer to 10 indicated higher levels of subjective pain intensity. Duration of stomatitis symptoms in the oral cavity was recorded in months. Chronic pain was defined as pain persisting for more than six months, indicating the chronicity of the condition [20]. The lesion sites were categorized into the tongue, lips, gingiva, palate, and entire mouth based on the areas where patients reported discomfort or pain. The number of lesion sites was also determined. Oral hygiene was categorized into three levels: good, acceptable, and poor. This classification was used to analyze the relationship between oral hygiene and the presence or abundance of Candida albicans in patients with oral candidiasis. This study also investigated systemic diseases known to affect salivary flow rate, specifically hypertension, diabetes, osteoporosis, and cardiovascular diseases. These data were recorded based on patient reports of diagnoses or medications used for these conditions. The presence and number of systemic diseases were examined to determine their effects on oral candidiasis.

3) Salivary flow rate and xerostomia

Prior to the saliva sampling session, the participants were instructed to refrain from caffeine and nicotine for at least 4 hours and alcohol for at least 24 hours. Whole saliva samples, both stimulated and unstimulated, were collected between 9:30 and 11:30 a.m. to minimize diurnal variability. The mean time difference between waking up and collecting was 3 hours. All participants refrained from drinking alcohol the previous day and were instructed to abstain from eating, drinking, and brushing their teeth before the collection of saliva samples. The unstimulated whole salivary flow rate (UFR) was measured for 10 minutes using the spitting method. The stimulated whole salivary flow rate (SFR) was measured for 5 minutes while chewing 1 g of gum base after a 2-minute pre-stimulation period to remove saliva retained in the ducts. The UFR and SFR were expressed in mL/min [21, 22]. The diagnostic criteria for xerostomia were set at a UFR of 0.2 mL/min and an SFR of 0.7 mL/min [23, 24].

Statistical analysis

Data were analyzed using the Statistical Package for Social Sciences (SPSS) for Windows (version 26.0; IBM Corp., Armonk, NY, USA). Descriptive statistics were presented as mean ± standard deviation or as frequencies with percentages, as appropriate. To analyze the distribution of categorical data, we employed the χ2 test and Bonferroni correction for equality of proportions. A t-test was used to compare the means between the two groups. Spearman's correlation analysis was conducted to evaluate the strength of the association between two variables, where the absolute value of the correlation coefficient (r) indicates the strength of the correlation, ranging from − 1 to + 1, with values closer to 1 indicating a stronger correlation, and values closer to 0 indicating a weaker correlation. Receiver operating characteristic (ROC) curves were plotted, and the corresponding area under the curve (AUC) values were calculated to assess the performance of the models at the classification threshold (above the mean value of each laboratory parameter). AUC values were interpreted as follows: AUC = 0.5 (no discrimination), 0.6 ≥ AUC > 0.5 (poor discrimination), 0.7 ≥ AUC > 0.6 (acceptable discrimination), 0.8 ≥ AUC > 0.7 (excellent discrimination), and AUC > 0.9 (outstanding discrimination) [25]. A generalized linear model was used to investigate the correlation between oral candidiasis and other factors that were either significantly correlated with oral candidiasis or showed significant differences based on oral candidiasis. Beta weights (B), standard errors, p-values, and 95% confidence intervals (95% CIs) were investigated. The intra-rater reliability of muscle thickness and cross-sectional area measurements was assessed using the ICC coefficient, with a mean value of 0.84. A two-tailed p-value of less than 0.05 was considered statistically significant for all analyses.

Demographics

Of the 259 patients with stomatitis, 81 (31.27%) had oral candidiasis based on Candida albicans cultures. Regarding age, the stomatitis with oral candidiasis group (64.25 ± 14.66 years) was significantly older than the stomatitis without oral candidiasis group (57.73 ± 16.10 years) (p = 0.002). The proportion of females was significantly higher in the stomatitis with oral candidiasis group (male-to-female ratio = 1:5.75) than in the stomatitis without oral candidiasis group (male-to-female ratio = 1:2.87) (p = 0.048) (Table 1).

Table 1

Demographics and clinical characteristics
	Stomatitis without oral candidiasis (n = 178)	Stomatitis with oral candidiasis (n = 81)	p-value
Demographics
Age (years) ^a	57.73 ± 16.10	64.25 ± 14.66	0.002**
Sex ^b
Male	46 (25.8%)	12 (14.8%)	0.048*
Female	132 (74.2%)	69 (85.2%)	0.048*
Clinical symptoms
VAS (0–10) ^a	3.47 ± 3.07	3.89 ± 2.82	0.279
Symptom duration (months) ^a	16.39 ± 30.45	12.65 ± 35.12	0.033*
Chronicity ^b	94 (52.8%)	32 (39.5%)	0.047*
Lesion site
Tongue ^b	99 (55.6%)	43 (53.1%)	0.788
Buccal mucosa ^b	17 (9.6%)	11 (13.6%)	0.333
Lips ^b	8 (4.5%)	12 (14.8%)	0.010*
Gingiva ^b	6 (3.4%)	3 (3.7%)	1.000
Palate ^b	7 (3.9%)	1 (1.2%)	0.245
Entire mouth ^b	68 (38.2%)	28 (34.6%)	0.575
Number of lesion sites ^b	1.12 ± 0.47	1.17 ± 0.52	0.418
Oral hygiene ^b
Good	39 (21.9%)	13 (16.0%)	0.547
Acceptable	126 (70.8%)	62 (76.5%)
Poor	13 (7.3%)	6 (7.4%)
^a Results were analyzed using t-tests. ^b Results were obtained using χ2 test between two age groups.
VAS: visual analogue scale.
P-value significance was set at < 0.05. p-value < 0.05, *p-value < 0.01.

Pain characteristics

The VAS for subjective pain intensity was higher in patients with stomatitis and oral candidiasis than those without, but the difference was not statistically significant (mean 3.89 ± 2.82 vs. 3.47 ± 3.07, p = 0.279).

Contrary to expectations, the symptom duration was significantly shorter in patients with stomatitis with oral candidiasis than those without (16.39 ± 30.45 months vs. 23.56 ± 36.72 months, p = 0.033). Additionally, the proportion of patients with symptoms of ‘chronicity’ was lower in the stomatitis with oral candidiasis group than in the stomatitis without oral candidiasis group (39.5% vs. 52.8%, p = 0.047). Further studies are needed to determine whether Candida albicans cause pain that prompts patients with stomatitis to seek medical attention sooner.

Regarding lesion sites, the most commonly reported discomfort was the tongue (stomatitis without oral candidiasis, 55.6%; stomatitis with oral candidiasis, 53.1%; p = 0.788). In stomatitis patients without oral candidiasis, the lesion sites were most frequently located on the tongue (55.6%), entire mouth (38.2%), buccal mucosa (9.6%), lips (4.5%), palate (3.9%), and gingiva (3.4%). In patients with stomatitis and oral candidiasis, the lesions were most frequently located on the tongue (53.1%), entire mouth (34.6%), lips (14.8%), buccal mucosa (13.6%), gingiva (3.7%), and palate (1.2%). The lips were the only site where lesions were more frequently found in patients with oral candidiasis than those without (4.5% vs. 14.8%, p = 0.01).

Over 90% of the patients with stomatitis have acceptable to good levels of oral hygiene. There was no significant difference in the distribution of good, acceptable, and poor levels between the two groups (p = 0.547). Both groups had acceptable levels of oral hygiene (> 70%). Good oral hygiene was observed in 21.9% of the patients with stomatitis only and in 16.0% of the patients with both stomatitis and oral candidiasis. Poor oral hygiene was observed in 7.3% of patients with stomatitis only and 7.4% of patients with both stomatitis and oral candidiasis (Table 1).

Salivary flow rate and xerostomia

Regarding salivary flow rates, the UFR and SFR were significantly lower in patients with oral candidiasis than those without. UFR was significantly lower in the stomatitis with oral candidiasis group (0.36 ± 0.32 mL/min) compared to the stomatitis without oral candidiasis group (0.47 ± 0.28 mL/min) (p = 0.006). Similarly, SFR was significantly lower in the stomatitis with oral candidiasis group (1.21 ± 0.68 mL/min) compared to the stomatitis without oral candidiasis group (1.41 ± 0.69 mL/min) (p = 0.032). For reference, the UFR of all stomatitis patients was 0.43 ± 0.29 mL/min, and the SFR was 1.34 ± 0.69 mL/min. The proportion of xerostomia based on UFR (xerostomia the UFR) was significantly higher in the stomatitis with oral candidiasis group (49.4%) than in the stomatitis without oral candidiasis group (18.5%) (p < 0.001). Similarly, the proportion of xerostomia based on SFR (xerostomia_SFR) was significantly higher in the stomatitis with oral candidiasis group (27.2%) than in the stomatitis without oral candidiasis group (10.7%) (p < 0.001) (Table 2).

Table 2

Salivary flow rate, xerostomia, and systemic diseases
	Stomatitis without oral candidiasis (n = 178)	Stomatitis with oral candidiasis (n = 81)	p-value
Salivary flow rate
UFR (mL/min) ^a	0.47 ± 0.28	0.36 ± 0.32	0.006**
SFR (mL/min) ^a	1.41 ± 0.69	1.21 ± 0.68	0.032*
Xerostomia_UFR ^b	33 (18.5%)	40 (49.4%)	< 0.001***
Xerostomia_SFR ^b	19 (10.7%)	22 (27.2%)	0.002**
Systemic diseases
Hypertension ^b	66 (37.1%)	30 (37.0%)	1.000
Diabetes mellitus ^b	21 (11.8%)	11 (13.6%)	0.687
Osteoporosis ^b	9 (5.1%)	2 (2.5%)	0.511
Cardiovascular diseases ^b	14 (7.9%)	3 (3.7%)	0.283
Number of systemic diseases ^a	0.62 ± 0.84	0.57 ± 0.71	0.619
^a Results were analyzed using t-tests. ^b Results were obtained using χ2 test between two age groups.
UFR: unstimulated salivary flow rate, SFR: stimulated salivary flow rate.
P-value significance was set at < 0.05. p-value < 0.05, p-value < 0.01, **p-value < 0.001.

Systemic diseases

No significant differences were observed in the distribution of systemic diseases according to the presence of oral candidiasis. In the stomatitis without oral candidiasis group, the distribution was as follows: hypertension (37.1%), diabetes (11.8%), cardiovascular disease (7.9%), and osteoporosis (5.1%). In the stomatitis with oral candidiasis group, the distributions were as follows: hypertension (37.0%), diabetes mellitus (13.6%), cardiovascular disease (3.7%), and osteoporosis (2.5%). There was also no significant difference in the number of systemic diseases between the two groups (p = 0.619) (Table 2).

Factors associated with oral candidiasis

When considering oral candidiasis in all patients, an increase in Candida albicans significantly correlated with advancing age (r = 0.219, p < 0.01). Additionally, there were significant positive correlations between age and the number of systemic diseases (r = 0.471, p < 0.001) and poor oral hygiene (r = 0.293, p < 0.001). The UFR and SFR were also significantly positively correlated with each other (r = 0.488, p < 0.001). Interestingly, in cases of oral candidiasis, the increase in the amount of Candida albicans was significantly correlated with a decrease in UFR (r=-0.265, p < 0.001) and SFR (r=-0.150, p = 0.016) (Fig. 2). This indicates that a decrease in salivary flow rate and the presence of xerostomia is associated with increased Candida albicans.

The cutoff value for oral candidiasis

To predict the presence of oral candidiasis, we performed ROC curve analysis using age, UFR, and SFR (which showed the most significant differences based on oral candidiasis) as independent variables and oral candidiasis as the dependent variable. The prediction accuracy for oral candidiasis based on age was 62.2% (AUC = 0.622, 95% CI: 0.547–0.696, p = 0.002), with a cut-off value of 64.50 years for age. The prediction accuracy based on the UFR was 65.8% (AUC = 0.658, 95% CI: 0.582–0.734, p < 0.001), with a cutoff value of 0.3350 mL/min for UFR. The prediction accuracy based on SFR was 58.7% (AUC = 0.587, 95% CI: 0.510–0.663, p = 0.025), with a cutoff value of 1.150 mL/min for SFR. Thus, the predictive accuracy for oral candidiasis based on the UFR was 7.1% higher than that based on the SFR (Fig. 3).

Distribution of oral candidiasis and xerostomia by age

The incidence of oral candidiasis significantly increased in the 80s age group (22.2%) compared to that in the 10s (22.2%), 20s (0.0%), and 30s (20.0%) age groups (p = 0.047) (Fig. 4). When examining the quantity of Candida albicans more closely, the proportion of moderate (22.2%) and high (33.3%) Candida albicans was higher in the 80s age group. In contrast, the distribution of moderate to many Candida albicans in the 10s–30s age groups was nearly 0.0%. However, there was no significant difference in the overall distribution of the four categories of Candida albicans (none, a few, moderate, and many) across different age groups (p = 0.238).

When examining the distribution of xerostomia by age group, the xerostomia_UFR, based on a threshold of 0.2 mL/min for UFR, showed a statistically significant difference (p = 0.044). The xerostomia _SFR, based on a threshold of 0.7 mL/min, is also differently distributed by age groups (p = 0.005) (Fig. 4). The presence of xerostomia, based on the UFR and SFR, increased with age. The prevalence of Xerostomia_UFR was 11.1% in the 10s, 0.0% in the 20s, 20.0% in the 30s, 23.3% in the 40s, 27.1% in the 50s, 27.9% in the 60s, and 29.2% in the 70s, showing a significant increase to 61.1% in the 80s. The prevalence of Xerostomia_SFR was 0.0% among those in their 10s and 20s, 10.0% among those in their 30s, 20.0% among those in their 40s, 15.3% among those in their 50s, 13.1% among those in their 60s, and 12.3% among those in their 70s, with a significant increase to 50% in the 80s. More than half of stomatitis patients aged > 80 years had xerostomia (Table 3).

Table 3

Distribution of oral candidiasis and xerostomia according to age
	10s (n = 9)	20s (n = 7)	30s (n = 10)	40s (n = 30)	50s (n = 59)	60s (n = 61)	70s (n = 65)	80s (n = 18)	p-value
Proportion of oral candidiasis
Oral candidiasis	2 (22.2%)	0 (0.0%)	2 (20.0%)	8 (26.7%)	16 (27.1%)	17 (27.9%)	25 (38.5%)	11 (61.1%)	0.047*
Quantity of Candida albicans
None	7 (77.8%)	6 (85.7%)	8 (0.8%)	22 (73.3%)	43 (72.9%)	44 (72.1%)	40 (61.5%)	7 (38.9%)	0.238
A few	2 (22.2%)	1 (14.3%)	1 (0.1%)	3 (0.1%)	7 (11.9%)	7 (11.5%)	10 (15.4%)	1 (5.6%)
Moderate	0 (0.0%)	0 (0.0%)	1 (0.1%)	2 (6.7%)	5 (8.5%)	3 (4.9%)	5 (7.7%)	4 (22.2%)
Many	0 (0.0%)	0 (0.0%)	0 (0.0%)	3 (10.0%)	4 (6.8%)	7 (11.5%)	10 (15.4%)	6 (33.3%)
Xerostomia
Xerostomia_UFR	1 (11.1%)	0 (0.0%)	2 (20.0%)	7 (23.3%)	18 (27.1%)	17 (27.9%)	19 (29.2%)	11 (61.1%)	0.044*
Xerostomia_SFR	0 (0.0%)	0 (0.0%)	1 (10.0%)	6 (20.0%)	9 (15.3%)	8 (13.1%)	8 (12.3%)	9 (50.0%)	0.005**
Results were obtained using repeated χ2 test between age groups.
UFR: unstimulated salivary flow rate, SFR: stimulated salivary flow rate.

Generalized linear model for oral candidiasis

When a generalized linear model was performed to predict oral candidiasis, significant predictors were xerostomia_UFR (B = 0.328, 95% CI: 0.177–0.480, p < 0.001) and lesions on the lips (B = 0.280, 95% CI: 0.085–0.475, p < 0.005). Age (B = 0.001, 95% PI: -0.017–0.019, p = 0.907) was not a significant predictor of oral candidiasis when considered alongside the UFR. Thus, when multiple parameters were included in the analysis, only xerostomia based on UFR and lip lesions significantly predicted oral candidiasis. This suggests that the salivary flow rate in a neutral state without chewing stimulation is most closely associated with the occurrence of oral candidiasis (Table 4).

Table 4

Generalized linear model for predicting oral candidiasis
Parameter	B	SE	95% CI lower	95% CI upper	p-value
Female [ref.=male]	0.110	0.065	-0.017	0.237	0.090
Xerostomia_UFR [ref.=none]	0.328	0.077	0.177	0.480	< 0.001***
Xerostomia_SFR [ref.=none]	0.059	0.092	-0.120	0.239	0.517
Age	0.001	0.009	-0.017	0.019	0.907
Symptom duration	0.016	0.049	-0.080	0.112	0.743
Lips [ref.=none]	0.280	0.099	0.085	0.475	0.005**
Constant	0.178	0.016	0.150	0.212	0.168
The results were obtained using a generalized linear model. The likelihood ratio chi-square statistic (G²) was 49.014 with p < 0.001.
UFR, unstimulated salivary flow rate; SFR, stimulated salivary flow rate; CI, confidence interval.
P-value significance was set at < 0.05. p-value < 0.0, *p-value < 0.001.

Approximately one-third of the patients with stomatitis had oral candidiasis. Patients with oral candidiasis were significantly older than those without candidiasis. The unstimulated and stimulated salivary flow rates were significantly lower in patients with oral candidiasis. The proportion of patients with xerostomia, based on both unstimulated and stimulated salivary flow rates, was significantly higher in the oral candidiasis group. The predictive accuracy of oral candidiasis based on age, UFR, and SFR was assessed, and the UFR showed the highest predictive accuracy. From the generalized linear model, xerostomia based on the UFR was identified as a significant predictor of oral candidiasis. Additionally, with increasing age, the occurrence of xerostomia based on the UFR and oral candidiasis increased. Contrary to our expectations, age alone was not a factor that increased the likelihood of oral candidiasis, and there was no significant difference in the subjective pain intensity between patients with and without oral candidiasis. This study is valuable as it diagnoses oral candidiasis in patients with stomatitis through direct culture of Candida albicans, investigates its incidence rate, and comprehensively examines its relationship with xerostomia based on salivary flow rate, patient age, and systemic diseases.

First, the oral cavity serves as a marker area that reflects the health of the oral cavity and the entire body. It is often considered a window to the body because oral manifestations can indicate many systemic diseases or conditions [26]. The first line of defense against microbial infection or inflammation of the oral cavity, as well as physical friction and chemical stimulation, includes saliva and oral mucosa, which are essential for the human body [27]. The average age of the stomatitis patients in this study was relatively high (59.77 years, with the prevalence of xerostomia and candidiasis increasing with age. Major aphthous stomatitis predominantly occurs in individuals aged 35–59, whereas minor aphthous stomatitis is more common in individuals aged < 30 [4, 28]. Although the precise prevalence of stomatitis is not well-documented, it has been theoretically posited that the likelihood of developing oral diseases increases with age.

As age increases, the likelihood of developing oral mucosal diseases increases due to decreased saliva secretion, difficulties in maintaining oral hygiene, the presence of dental prostheses, smoking, alcohol consumption, polypharmacy, and an increase in systemic diseases [29]. The salivary flow rate of the submandibular and sublingual salivary glands decreases with age. Still, the parotid gland, responsible for 90% of saliva production, shows no significant change in salivary flow rate with age [30]. Xerostomia can occur at any age; however, approximately 25% of the elderly suffer from oral dryness and related complaints [31]. The decrease in salivary flow rate with increasing age has not yet led to consistent conclusions owing to the comorbidities and complexities associated with systemic diseases in the elderly. Regarding the oral mucosa, even when it appears clinically normal, aging can cause changes, such as a reduction in the thickness of the epithelial and keratinized layers [32]. The mucosa becomes thinner, smoother, more fragile, and more susceptible to infection by Candida albicans and other microorganisms. Consequently, they are more prone to damage and exhibit slower healing [33]. Therefore, in humans, the reduction in saliva, stomatitis, and oral candidiasis can be closely related, with aging being a significant factor to consider in these relationships.

Among the various analytical methods, unstimulated salivary flow rate has consistently emerged as a predictor of oral candidiasis in patients with stomatitis. Many patients experienced xerostomia (28.2% xerostomia_UFR and 15.8% xerostomia_SFR), and the UFR had a higher weight on xerostomia than the SFR. The normal range for UFR is 0.3–0.4 mL/min [31]. Generally, xerostomia is diagnosed when UFR is below 0.1–0.2 mL/min [24]. However, when employing advanced machine learning techniques, the absolute salivary flow rate that induces xerostomia varies according to the patient's age, sex, and the number of systemic diseases [34]. The cutoff value of the UFR for predicting oral candidiasis was 0.3350 mL/min. This was higher than the threshold for diagnosing dry mouth based on the UFR and lower than the lowest point of the normal UFR reference range. Complex factors of the stomatitis patient must be considered. An adequate amount of saliva is crucial for oral health because it contains various antimicrobial constituents, antibodies, enzymes, hormones, growth factors, lubricants, and water [35]. These components enable the saliva to perform various functions, including antifungal action, immunological protection, and lubrication. Studies have indicated that decreased unstimulated or residual saliva is associated with oral dryness [36, 37]. Additionally, the microbiome profile differs, and species diversity is lower in unstimulated saliva than in stimulated saliva [38]. However, further studies with larger sample sizes are required to examine the compositional differences between unstimulated and stimulated saliva. The key factors causing the quantitative and qualitative differences between saliva under these two conditions remain unknown.

In this study, we focused on the relationship between the growth of Candida albicans and the presence of oral candidiasis in patients with stomatitis. However, there is a significant lack of research on the role of Candida albicans in patients with stomatitis. Oral candidiasis is a common opportunistic infection of the oral cavity caused by overgrowth of Candida species, the most common being Candida albicans [39]. Local factors associated with oral candidiasis include impaired salivary gland function, xerostomia, and unsanitized dental prostheses [40]. In a recent meta-analysis, xerostomic patients had a three-fold higher risk of oral Candida growth and candidiasis development than controls [12]. The tongue is the most common lesion site for stomatitis symptoms, regardless of oral candidiasis. The tongue is a suitable habitat for microorganisms [41]. Metabolic sources such as food particles and shed cells, as well as environmental factors such as humidity and temperature, create an optimal environment for microbial growth. Microorganisms that colonize the islets may provide a putative mechanism for oral pain or discomfort. Systemic factors for oral candidiasis include antibiotics and some other drugs, aging, malnutrition, and immunosuppression [19, 42]. The prevalence of oral candidiasis in the elderly ranges from 13 to 47% [42]. In this study, oral candidiasis occurred in 31.3% of patients with stomatitis, with a steep increase observed in 27.9% of patients in their 60s, 38.5% of those in their 70s, and 61.1% of those in their 80s. Individuals who are extremely old or have an immature or weakened immune system are particularly susceptible to candidiasis [43]. Oral carriage of Candida spp. is generally found in 30–45% of the healthy adult population [39]. In this study, the age group in which Candida spp. occurred beyond the normal range (up to 45%) was > 80 years. However, the cutoff value for predicting oral candidiasis in patients with stomatitis was 64.50 years. To clarify our findings and link them with previous research, the influence of microorganisms residing on the tongue coating or in the fissures of the tongue on oral stomatitis warrants further investigation in neonates and infants with immature immune systems as well as in elderly patients with compromised or fragile immune systems.

Candida spp. leave the oral cavity in the bloodstream and move to various organs in the body. Overgrowth of Candida spp. in the oral cavity may lead to their dissemination to distant organs, potentially having clinical implications at a distance as well [44]. Systemic candidiasis is less frequent than oral candidiasis but has a mortality rate of 71–79% [45]. Unlike young and healthy individuals, Candida albicans can cause fatal outcomes in frail and debilitated elderly patients, necessitating prompt diagnosis and treatment. This study was conducted during the ongoing COVID-19 pandemic. During this period, several cases of oral candidiasis in SARS-CoV-2-positive individuals have been reported [46, 47]. The immune-inflammatory hypo-reactions and immunosuppression found in individuals with COVID-19 could favor the proliferation of Candida species and subsequent infections [48]. Therefore, to prevent the sequelae of systemic candidiasis, prompt management and control of oral candidiasis is imperative. Further research is needed to understand the relationship between Candida albicans and other microbes, their role in the overall microbiome profile, and the systemic and oral health conditions of the host.

The limitations of this study include the uneven distribution of patients across different age groups despite the large sample size of over 250 participants. Future studies with a larger number of participants evenly distributed across age groups are required to mitigate potential biases in age-related analyses. Additionally, we did not comprehensively examine the impact of oral candidiasis on pain intensity, symptom chronicity, or overall quality of life in patients with stomatitis. Advanced and sophisticated analytical methods are required to identify individual factors contributing to the occurrence of oral candidiasis in patients with stomatitis and to elucidate the interrelationships between these factors. Furthermore, a multicenter prospective study with healthy controls, aligned with the concept and perspective of this research, would provide more robust support for our findings.

A notable strength of this study is the scientific demonstration that oral candidiasis in patients with stomatitis has significant clinical implications. In patients with stomatitis, oral candidiasis is associated with a decrease in the salivary flow rate and an increase in age. Specifically, the cut-off value for predicting oral candidiasis based on unstimulated salivary flow was 0.3350 mL/min. Additionally, oral candidiasis occurred significantly more frequently with increasing age in patients with stomatitis, with a cutoff value of 64.50 years for age. Another strength of this study is the validation of our hypotheses across a broad age range, from teenagers to individuals in their 80s. Expanding on this study, utilizing cutting-edge oral microbiome analysis to derive specific profiles of stomatitis patients and microorganisms related to Candida albicans will be instrumental in enhancing our understanding of this disease.

Acknowledgments:

The authors thank Sung-Woo Lee of the Department of Oral Medicine and Oral Diagnosis at the Seoul National University School of Dentistry.

Funding:

This work was supported by the Korea Medical Device Development Fund grant funded by the Korean government (Ministry of Science and ICT, Ministry of Trade, Industry, and Energy, Ministry of Health & Welfare, Republic of Korea, Ministry of Food and Drug Safety) (Project Number: KMDF_PR_20200901_0023, 9991006696).

Author contributions:

Y. -H. L. and S.-W.L. wrote the manuscript. Y.-H.L., S. S, and T.-S.K. contributed to the data acquisition and analysis. Y.-H.L. and S.-W.L. contributed to data interpretation. Y.-H.L., H.-K. P., and S.-W.L. provided expertise. Y. H. L. contributed to the figures. Y.-H.L. and H.-K. P. provided expertise and contributed to revisions. All the authors have read and agreed to the published version of this manuscript.

Data Availability Statement:

The datasets used and/or analyzed in the current study are available from the corresponding author upon reasonable request.

Conflict of Interests: The author declares no conflict of interests.

Ethics declaration:

The research protocol for this study was reviewed to ensure compliance with the principles of the Declaration of Helsinki and approved by the Institutional Review Board of Kyung Hee University Dental Hospital in Seoul, South Korea (KHD IRB, IRB No-KH-DT23022). Informed consent was obtained from all participants.

Consent to participate:

N/A

Consent to publish:

The author has read and agreed to the published version of the manuscript.

Edgar NR, Saleh D, Miller RA. Recurrent Aphthous Stomatitis: A Review. J Clin Aesthet Dermatol. 2017;10(3):26–36.
Gendreau L, Loewy ZG. Epidemiology and etiology of denture stomatitis. J Prosthodont. 2011;20(4):251–60.
Kaur R, Behl AB, Punia RS, Nirav K, Singh KB, Kaur S. Assessment of Prevalence of Recurrent Aphthous Stomatitis in the North Indian Population: A Cross-Sectional Study. J Pharm Bioallied Sci. 2021;13(Suppl 1):S363–6.
Manoj MA, Jain A, Madtha SA, Cherian TM. Prevalence and risk factors of recurrent aphthous stomatitis among college students at Mangalore, India. PeerJ. 2023;11:e14998.
Sheetal A, Hiremath VK, Patil AG, Sajjansetty S, Kumar SR. Malnutrition and its oral outcome - a review. J Clin Diagn Res. 2013;7(1):178–80.
Dose AM. The symptom experience of mucositis, stomatitis, and xerostomia. Semin Oncol Nurs. 1995;11(4):248–55.
Volkov I, Rudoy I, Abu-Rabia U, Masalha T, Masalha R. Case report: Recurrent aphthous stomatitis responds to vitamin B12 treatment. Can Fam Physician. 2005;51(6):844–5.
Rohani B. Oral manifestations in patients with diabetes mellitus. World J Diabetes. 2019;10(9):485–9.
Abiko Y, Paudel D, Matsuoka H, Moriya M, Toyofuku A. Psychological Backgrounds of Medically Compromised Patients and Its Implication in Dentistry: A Narrative Review. Int J Environ Res Public Health 2021, 18(16).
Qi X, Northridge ME, Hu M, Wu B. Oral health conditions and COVID-19: A systematic review and meta-analysis of the current evidence. Aging Health Res. 2022;2(1):100064.
Furness S, Bryan G, McMillan R, Birchenough S, Worthington HV. Interventions for the management of dry mouth: non-pharmacological interventions. Cochrane Database Syst Rev. 2013;2013(9):Cd009603.
Molek M, Florenly F, Lister INE, Wahab TA, Lister C, Fioni F. Xerostomia and hyposalivation in association with oral candidiasis: a systematic review and meta-analysis. Evidence-Based Dentistry; 2022.
Salerno C, Pascale M, Contaldo M, Esposito V, Busciolano M, Milillo L, Guida A, Petruzzi M, Serpico R. Candida-associated denture stomatitis. Med Oral Patol Oral Cir Bucal. 2011;16(2):e139–143.
Sharon V, Fazel N. Oral candidiasis and angular cheilitis. Dermatol Ther. 2010;23(3):230–42.
Goregen M, Miloglu O, Buyukkurt MC, Caglayan F, Aktas AE. Median rhomboid glossitis: a clinical and microbiological study. Eur J Dent. 2011;5(4):367–72.
Gleiznys A, Zdanavičienė E, Žilinskas J. Candida albicans importance to denture wearers. A literature review. Stomatologija. 2015;17(2):54–66.
Liu Y, Mittal R, Solis NV, Prasadarao NV, Filler SG. Mechanisms of Candida albicans trafficking to the brain. PLoS Pathog. 2011;7(10):e1002305.
Snarr BD, Drummond RA, Lionakis MS. It's all in your head: antifungal immunity in the brain. Curr Opin Microbiol. 2020;58:41–6.
Dekkers BGJ, Veringa A, Marriott DJE, Boonstra JM, van der Elst KCM, Doukas FF, McLachlan AJ, Alffenaar JC. Invasive Candidiasis in the Elderly: Considerations for Drug Therapy. Drugs Aging. 2018;35(9):781–9.
Treede RD, Rief W, Barke A, Aziz Q, Bennett MI, Benoliel R, Cohen M, Evers S, Finnerup NB, First MB, et al. A classification of chronic pain for ICD-11. Pain. 2015;156(6):1003–7.
Lee Y-H, Won JH, Auh QS, Noh Y-K, Lee S-W. Prediction of xerostomia in elderly based on clinical characteristics and salivary flow rate with machine learning. Sci Rep. 2024;14(1):3423.
Lee YH, Kim YY, Chang JY, Kho HS. Changes in oral mucosal MUC1 expression and salivary hormones throughout the menstrual cycle. Oral Dis. 2015;21(8):962–8.
Villa A, Connell CL, Abati S. Diagnosis and management of xerostomia and hyposalivation. Ther Clin Risk Manag. 2015;11:45–51.
Agostini BA, Cericato GO, Silveira ERD, Nascimento GG, Costa FDS, Thomson WM, Demarco FF. How Common is Dry Mouth? Systematic Review and Meta-Regression Analysis of Prevalence Estimates. Braz Dent J. 2018;29(6):606–18.
Lasko TA, Bhagwat JG, Zou KH, Ohno-Machado L. The use of receiver operating characteristic curves in biomedical informatics. J Biomed Inform. 2005;38(5):404–15.
Babu NC, Gomes AJ. Systemic manifestations of oral diseases. J Oral Maxillofac Pathol. 2011;15(2):144–7.
Marcotte H, Lavoie MC. Oral microbial ecology and the role of salivary immunoglobulin A. Microbiol Mol Biol Rev. 1998;62(1):71–109.
Chiang C-P, Yu-Fong Chang J, Wang Y-P, Wu Y-H, Wu Y-C, Sun A. Recurrent aphthous stomatitis – Etiology, serum autoantibodies, anemia, hematinic deficiencies, and management. J Formos Med Assoc. 2019;118(9):1279–89.
Gonsalves WC, Wrightson AS, Henry RG. Common oral conditions in older persons. Am Fam Physician. 2008;78(7):845–52.
Affoo RH, Foley N, Garrick R, Siqueira WL, Martin RE. Meta-Analysis of Salivary Flow Rates in Young and Older Adults. J Am Geriatr Soc. 2015;63(10):2142–51.
Vissink A, Spijkervet FK, Van Nieuw Amerongen A. Aging and saliva: a review of the literature. Spec Care Dentist. 1996;16(3):95–103.
Abu Eid R, Sawair F, Landini G, Saku T. Age and the architecture of oral mucosa. Age (Dordr). 2012;34(3):651–8.
Qi W, Dong N, Wu L, Zhang X, Li H, Wu H, Ward N, Yu J, Liu H, Wang J, et al. Promoting oral mucosal wound healing using a DCS-RuB(2)A(2) hydrogel based on a photoreactive antibacterial and sustained release of BMSCs. Bioact Mater. 2023;23:53–68.
Lee YH, Won JH, Auh QS, Noh YK, Lee SW. Prediction of xerostomia in elderly based on clinical characteristics and salivary flow rate with machine learning. Sci Rep. 2024;14(1):3423.
de Almeida Pdel V, Grégio AM, Machado MA, de Lima AA, Azevedo LR. Saliva composition and functions: a comprehensive review. J Contemp Dent Pract. 2008;9(3):72–80.
Löfgren CD, Wickström C, Sonesson M, Lagunas PT, Christersson C. A systematic review of methods to diagnose oral dryness and salivary gland function. BMC Oral Health. 2012;12:29.
Lee SK, Lee SW, Chung SC, Kim YK, Kho HS. Analysis of residual saliva and minor salivary gland secretions in patients with dry mouth. Arch Oral Biol. 2002;47(9):637–41.
Gomar-Vercher S, Simón-Soro A, Montiel-Company JM, Almerich-Silla JM, Mira A. Stimulated and unstimulated saliva samples have significantly different bacterial profiles. PLoS ONE. 2018;13(6):e0198021.
Akpan A, Morgan R. Oral candidiasis. Postgrad Med J. 2002;78(922):455–9.
Bianchi CM, Bianchi HA, Tadano T, Paula CR, Hoffmann-Santos HD, Leite DP Jr., Hahn RC, FACTORS RELATED TO ORAL CANDIDIASIS IN ELDERLY USERS AND NON-USERS OF REMOVABLE DENTAL PROSTHESES. Rev Inst Med Trop Sao Paulo. 2016;58:17.
Kennedy MS, Chang EB. The microbiome: Composition and locations. Prog Mol Biol Transl Sci. 2020;176:1–42.
Laurent M, Gogly B, Tahmasebi F, Paillaud E. [Oropharyngeal candidiasis in elderly patients]. Geriatr Psychol Neuropsychiatr Vieil. 2011;9(1):21–8.
Weerasuriya N, Snape J. Oesophageal candidiasis in elderly patients: risk factors, prevention and management. Drugs Aging. 2008;25(2):119–30.
Talapko J, Juzbašić M, Matijević T, Pustijanac E, Bekić S, Kotris I, Škrlec I. Candida albicans-The Virulence Factors and Clinical Manifestations of Infection. J Fungi (Basel) 2021, 7(2).
Patil S, Rao RS, Majumdar B, Anil S. Clinical Appearance of Oral Candida Infection and Therapeutic Strategies. Front Microbiol. 2015;6:1391.
Arastehfar A, Carvalho A, Nguyen MH, Hedayati MT, Netea MG, Perlin DS, Hoenigl M. COVID-19-Associated Candidiasis (CAC): An Underestimated Complication in the Absence of Immunological Predispositions? J Fungi (Basel) 2020, 6(4).
Di Spirito F, Iandolo A, Amato A, Caggiano M, Raimondo A, Lembo S, Martina S. Prevalence, Features and Degree of Association of Oral Lesions in COVID-19: A Systematic Review of Systematic Reviews. Int J Environ Res Public Health 2022, 19(12).
Pisano M, Romano A, Di Palo MP, Baroni A, Serpico R, Contaldo M. Oral Candidiasis in Adult and Pediatric Patients with COVID-19. Biomedicines 2023, 11(3).

No competing interests reported.

Download PDF

Version 1

posted

You are reading this latest preprint version

The Impact of Reduced Salivary Flow Rate and Aging on Oral Candidiasis in Patients with Stomatitis

Status:

Version 1

Abstract

Figures

INTRODUCTION

METHODS

Study population and study design

1) Diagnosis of oral candidiasis

2) Clinical characteristics

3) Salivary flow rate and xerostomia

Statistical analysis

RESULTS

Demographics

Pain characteristics

Salivary flow rate and xerostomia

Systemic diseases

Factors associated with oral candidiasis

The cutoff value for oral candidiasis

Distribution of oral candidiasis and xerostomia by age

Generalized linear model for oral candidiasis

DISCUSSION

Conclusion

Declarations

References

Additional Declarations

Status:

Version 1